Topic: Xylem and Phloem Transport; Subtopic: Directionality and Element Mobility
Keyword Definitions:
Phloem: Vascular tissue responsible for translocation of organic solutes, mainly sucrose, from source to sink in plants.
Xylem: Vascular tissue that conducts water and dissolved minerals upward from roots to aerial parts of plants.
Translocation: The movement of organic nutrients through phloem from photosynthetic tissues to other plant parts.
Bidirectional Transport: Movement of substances in two directions, as seen in xylem for water and minerals under specific conditions.
Unidirectional Transport: Movement of substances in a single direction, as seen in phloem sap from source to sink.
Mobile Elements: Nutrients that can be transported from older leaves to newer tissues when deficient.
Immobile Elements: Nutrients that remain in older tissues and cannot be readily remobilized to young leaves.
Lead Question – 2023 (Manipur)
Given below are two statements:
I: The process of translocation through phloem is unidirectional but through xylem, it is bidirectional.
II: The most readily mobilized elements are phosphorus, sulphur, nitrogen and potassium.
In light of the above statements, choose the most appropriate answer from the options given below:
1. Statement I is correct but Statement II is correct
2. Statement I is incorrect but Statement II is correct
3. Both Statement I and Statement II are correct
4. Both Statement I and Statement II are incorrect
Explanation: Translocation in phloem is generally unidirectional, moving nutrients from sources (like leaves) to sinks (such as roots, fruits, and growing tissues). Xylem transport, primarily for water and minerals, is mostly upward but can exhibit limited bidirectional movement under certain conditions. Elements like nitrogen, phosphorus, potassium, and sulphur are highly mobile within plants and can be remobilized from older to younger tissues. Both statements are factually correct and highlight essential differences between xylem and phloem transport mechanisms as well as nutrient mobility, which are crucial for understanding plant nutrition and physiology. Correct answer: 3. Both Statement I and Statement II are correct.
1. Single Correct Answer MCQ:
Which vascular tissue exhibits unidirectional transport of organic solutes?
1. Xylem
2. Phloem
3. Cambium
4. Epidermis
Explanation: Phloem conducts translocation of organic nutrients from source to sink in a unidirectional manner, unlike xylem which primarily transports water upward. Correct answer: 2. Phloem.
2. Single Correct Answer MCQ:
Which element is most readily remobilized within plants?
1. Calcium
2. Sulphur
3. Boron
4. Iron
Explanation: Sulphur is among the highly mobile elements along with nitrogen, phosphorus, and potassium, allowing remobilization from older to younger tissues. Correct answer: 2. Sulphur.
3. Single Correct Answer MCQ:
Xylem transport is primarily:
1. Unidirectional
2. Bidirectional
3. Lateral
4. Non-directional
Explanation: Xylem primarily conducts water and minerals upward from roots to shoots, but under certain physiological conditions, some bidirectional movement can occur. Correct answer: 2. Bidirectional.
4. Single Correct Answer MCQ:
Which nutrient is immobile in plants?
1. Potassium
2. Phosphorus
3. Calcium
4. Nitrogen
Explanation: Calcium is largely immobile in plants and remains in older tissues; deficiency symptoms appear in young leaves. Correct answer: 3. Calcium.
5. Single Correct Answer MCQ:
Translocation in phloem occurs from:
1. Sink to Source
2. Source to Sink
3. Root to Leaf only
4. Stem to Root only
Explanation: Phloem translocation moves sugars and other organic molecules from sources like leaves to sinks such as roots, fruits, and growing tissues. Correct answer: 2. Source to Sink.
6. Single Correct Answer MCQ:
Which element is mobile and deficiency symptoms appear first in older leaves?
1. Nitrogen
2. Calcium
3. Iron
4. Boron
Explanation: Nitrogen is mobile; during deficiency, older leaves show chlorosis first as nitrogen is remobilized to young tissues. Correct answer: 1. Nitrogen.
7. Assertion-Reason MCQ:
Assertion (A): Phloem translocation is unidirectional.
Reason (R): Organic solutes move from source to sink through sieve tubes.
1. Both A and R true, R explains A
2. Both A and R true, R does not explain A
3. A true, R false
4. A false, R true
Explanation: Phloem moves sugars from photosynthetic sources to sinks in a unidirectional manner. The reason correctly explains the assertion. Correct answer: 1.
8. Matching Type MCQ:
Match the element with its mobility:
A. Nitrogen – (i) Mobile
B. Calcium – (ii) Immobile
C. Phosphorus – (iii) Mobile
D. Boron – (iv) Immobile
1. A–i, B–ii, C–iii, D–iv
2. A–ii, B–i, C–iv, D–iii
3. A–iii, B–iv, C–i, D–ii
4. A–iv, B–iii, C–ii, D–i
Explanation: Nitrogen and phosphorus are mobile, while calcium and boron are immobile. Correct matching: A–i, B–ii, C–iii, D–iv. Correct answer: 1.
9. Fill in the Blanks MCQ:
Water transport in plants occurs mainly through ______, whereas sugar transport occurs through ______.
1. Phloem, Xylem
2. Xylem, Phloem
3. Cambium, Phloem
4. Phloem, Cambium
Explanation: Xylem conducts water and minerals primarily upward, while phloem translocates organic nutrients from source to sink. Correct answer: 2. Xylem, Phloem.
10. Choose the Correct Statements MCQ:
Statement I: Xylem transport is mostly upward but can be bidirectional under special conditions.
Statement II: Phosphorus and potassium are mobile nutrients in plants.
1. Both true
2. Both false
3. I true, II false
4. I false, II true
Explanation: Xylem primarily moves water upward but can exhibit bidirectional flow, and phosphorus and potassium are mobile elements remobilized to young tissues. Correct answer: 1.
Topic: Membrane Transport; Subtopic: Symport and Antiport Mechanisms
Symport: Transport mechanism where two molecules move in the same direction across a membrane via the same carrier protein.
Antiport: Transport mechanism where two molecules move in opposite directions across a membrane via the same carrier.
Carrier protein: Membrane protein that facilitates the movement of molecules across the lipid bilayer.
Membrane transport: The movement of ions, nutrients, or molecules across cell membranes.
Co-transport: General term for coupled transport of two substances, including symport and antiport.
Active transport: Movement of molecules against a concentration gradient using energy.
Passive transport: Movement of molecules along the concentration gradient without energy.
Gradient: Difference in concentration, charge, or pressure across a membrane driving transport.
Facilitated diffusion: Passive transport of molecules via carrier or channel proteins.
Lipid bilayer: Basic structural component of cell membranes that forms a barrier to molecules.
Membrane potential: Voltage difference across a membrane influencing movement of charged molecules.
Lead Question - 2023 (Manipur)
During symport, two different molecules move across the membrane:
1. in same direction with the help of different carriers located at a common site
2. in same direction with the help of different carriers located at different sites in the same cell
3. in same direction with the help of same carrier
4. in opposite direction with the help of same carrier
Explanation: Symport involves the simultaneous movement of two molecules in the same direction across the membrane using the same carrier protein. This is a type of co-transport that allows one molecule to move down its concentration gradient while driving the movement of another molecule against its gradient. Antiport, by contrast, moves molecules in opposite directions. Symport ensures coordinated transport and is crucial in processes like glucose-sodium uptake in intestines. Correct answer: 3.
1. Antiport differs from symport in that:
a) Molecules move in opposite directions via the same carrier
b) Molecules move in the same direction via the same carrier
c) Molecules move via different carriers in the same direction
d) It does not involve carrier proteins
Explanation: Antiport moves two different molecules across a membrane in opposite directions using the same carrier protein, unlike symport where molecules move together in the same direction. Both rely on carrier proteins. Choice a correctly identifies the opposite movement characteristic. Correct answer: a.
2. Sodium-glucose transport in intestines is an example of:
a) Symport
b) Antiport
c) Passive diffusion
d) Facilitated diffusion
Explanation: Sodium-glucose transport uses a symporter that moves glucose into intestinal epithelial cells along with sodium ions in the same direction. It couples movement of sodium down its gradient to drive glucose uptake. This is a classic symport example. Correct answer: a.
3. The energy driving symport usually comes from:
a) Gradient of one of the molecules
b) ATP directly
c) Light energy
d) Endocytosis
Explanation: Symport is a secondary active transport where the energy comes from the concentration gradient of one molecule, which drives the transport of another molecule against its gradient. ATP is not directly used. Correct answer: a.
4. Which type of transport does not require a carrier protein?
a) Simple diffusion
b) Symport
c) Antiport
d) Facilitated diffusion
Explanation: Simple diffusion occurs when molecules move along the concentration gradient directly through the lipid bilayer without the assistance of carrier proteins, unlike symport, antiport, or facilitated diffusion. Correct answer: a.
5. Symport transport is classified as:
a) Secondary active transport
b) Primary active transport
c) Simple diffusion
d) Endocytosis
Explanation: Symport is secondary active transport because it utilizes the energy stored in a concentration gradient of one molecule to drive the transport of another molecule against its gradient. Primary active transport directly uses ATP. Correct answer: a.
6. Which of the following is an example of symport?
a) Na⁺/glucose transport
b) Na⁺/Ca²⁺ exchanger
c) Oxygen diffusion
d) Endocytosis
Explanation: The sodium-glucose transporter carries both Na⁺ and glucose in the same direction into cells. Na⁺/Ca²⁺ exchanger is an antiport (opposite direction), oxygen diffusion is simple diffusion, and endocytosis is vesicular transport. Correct answer: a.
7. Assertion (A): Symport requires energy indirectly.
Reason (R): It utilizes the concentration gradient of one molecule to drive the transport of another molecule.
a) Both A and R are true, R explains A
b) Both A and R are true, R does not explain A
c) A is true, R is false
d) A is false, R is true
Explanation: Symport is secondary active transport, meaning it does not use ATP directly. Instead, it relies on the energy stored in the gradient of one molecule to drive the co-transport of another molecule in the same direction. Both assertion and reason are correct and the reason explains the assertion. Correct answer: a.
8. Match the transport type with its characteristic:
List-I: (A) Symport, (B) Antiport, (C) Simple diffusion, (D) Facilitated diffusion
List-II: (I) Moves two molecules in the same direction, (II) Moves two molecules in opposite directions, (III) Movement without carrier, (IV) Carrier-mediated movement along gradient
a) A-I, B-II, C-III
Topic: Transport in Plants; Subtopic: Phloem Transport and Mass Flow Hypothesis
Keyword Definitions:
• Mass flow: Bulk movement of water and solutes driven by pressure differences from source to sink.
• Diffusion: Passive movement of molecules from high to low concentration without energy input.
• Hydrostatic pressure: Pressure exerted by a fluid in a confined space.
• Phloem: Vascular tissue responsible for translocation of sugars and other organic substances in plants.
• Source: Plant tissue where sugars are produced or released, e.g., leaves.
• Sink: Plant tissue where sugars are utilized or stored, e.g., roots, fruits.
• Pressure gradient: Difference in pressure between two points that drives fluid movement.
• Positive hydrostatic pressure: Pressure that pushes fluid away from source.
• Negative hydrostatic pressure: Pressure that pulls fluid toward sink.
Lead Question - 2023 (Manipur)
Identify the correct statements regarding Mass flow hypothesis.
A: Mass flow is faster than diffusion.
B: Mass flow is the result of pressure difference between the end points.
C: Different substances involved in mass flow move at different paces.
D: Mass flow can result through either a positive or a negative hydrostatic pressure gradient.
Options:
1. (A), (C), (D) only
2. (B), (C), (D) only
3. (A), (B), (C) only
4. (A), (B), (D) only
Answer & Explanation: Option 4. Mass flow hypothesis explains translocation in phloem by bulk movement of solutes and water from source to sink due to pressure differences. It is faster than diffusion and can occur via positive or negative hydrostatic pressure gradients. Different solutes move together at the same pace, not individually. Understanding mass flow is essential for plant physiology, crop productivity, and sugar transport mechanisms. The hypothesis integrates pressure-driven movement with phloem structure, sink-source dynamics, and the regulation of nutrient distribution, highlighting its significance in plant growth, development, and energy allocation.
1. Single Correct Answer MCQ
Which tissue is responsible for mass flow in plants?
Options:
A. Xylem
B. Phloem
C. Cambium
D. Cortex
Answer & Explanation: Option B. Phloem is responsible for mass flow, transporting sugars and organic compounds from sources to sinks. Movement occurs through sieve tubes, driven by hydrostatic pressure differences. Understanding phloem transport is vital for crop productivity, carbon allocation, and plant physiology. It demonstrates how pressure gradients facilitate bulk movement, complementing diffusion and allowing efficient distribution of nutrients throughout the plant, ensuring growth, storage, and energy supply.
2. Single Correct Answer MCQ
Mass flow is primarily driven by:
Options:
A. Concentration gradient
B. Temperature difference
C. Hydrostatic pressure difference
D. Osmotic potential only
Answer & Explanation: Option C. Mass flow is driven by hydrostatic pressure differences between source and sink. Water and solutes move together as a bulk stream in the phloem. Understanding pressure-driven flow explains rapid transport over long distances. It is faster than diffusion and allows efficient nutrient allocation. This principle is fundamental for plant physiology, understanding phloem loading/unloading, and optimizing crop growth under various environmental conditions.
3. Single Correct Answer MCQ
Which of the following statements about mass flow is correct?
Options:
A. Each solute moves at its own pace
B. All solutes move together at the same rate
C. Solutes move only by diffusion
D. Solutes move against the pressure gradient
Answer & Explanation: Option B. In mass flow, all solutes move together at the same pace along the pressure gradient. Individual solutes do not move at different rates. This is fundamental to understanding phloem translocation, sink-source dynamics, and bulk transport efficiency. The concept contrasts with diffusion, emphasizing pressure-driven movement. It underpins plant growth, carbohydrate distribution, and energy allocation, highlighting the physiological significance of synchronized movement in vascular tissues.
4. Single Correct Answer MCQ
Positive hydrostatic pressure in phloem occurs at the:
Options:
A. Sink
B. Source
C. Root hair
D. Xylem
Answer & Explanation: Option B. Positive hydrostatic pressure develops at the source where sugars are loaded into sieve tubes, drawing water osmotically and pushing sap toward sinks. This mechanism drives mass flow, complementing phloem unloading. Understanding pressure gradients helps explain rapid nutrient movement, efficient transport, and distribution of carbohydrates to growing tissues. It is critical for crop physiology, sugar allocation, and maintaining growth and storage functions in plants.
5. Single Correct Answer MCQ
Which process is faster: mass flow or diffusion?
Options:
A. Mass flow
B. Diffusion
C. Both same
D. Neither
Answer & Explanation: Option A. Mass flow is faster than diffusion because it is pressure-driven bulk movement, allowing long-distance transport of solutes in phloem. Diffusion relies on concentration gradients and is slower over large distances. Mass flow efficiency is essential for nutrient allocation, sink-source dynamics, and supporting growth in tall plants. Understanding this speed difference is critical for plant physiology and optimizing transport processes under varying environmental conditions.
6. Single Correct Answer MCQ
Which factor can initiate mass flow in plants?
Options:
A. Light intensity
B. Hydrostatic pressure gradient
C. Soil pH
D. Temperature only
Answer & Explanation: Option B. Mass flow is initiated by hydrostatic pressure gradients between source and sink. Loading sugars at the source creates osmotic water influx, generating pressure that drives bulk sap movement toward sinks. Understanding this factor is essential for comprehending phloem transport, growth regulation, and nutrient allocation. It highlights the physical principles underlying plant physiology and the efficiency of pressure-driven translocation in vascular systems.
7. Assertion-Reason MCQ
Assertion (A): Mass flow allows faster transport than diffusion.
Reason (R): Pressure differences drive bulk movement of solutes.
Options:
A. Both A and R are true, R is the correct explanation of A
B. Both A and R are true, R is not the correct explanation of A
C. A is true, R is false
D. A is false, R is true
Answer & Explanation: Option A. Mass flow enables faster transport because hydrostatic pressure differences between source and sink drive bulk movement of solutes together with water. Unlike diffusion, which is slower and gradient-dependent, mass flow ensures rapid delivery of carbohydrates and nutrients to sinks. Understanding this relationship is critical for plant growth, sink-source regulation, and optimizing photosynthate distribution for energy allocation and development.
8. Matching Type MCQ
Match the following:
List-I List-II
(A) Source (I) Positive hydrostatic pressure
(B) Sink (II) Negative hydrostatic pressure
(C) Phloem (III) Vascular tissue transporting sugars
(D) Mass flow (IV) Bulk movement of solutes
Options:
1. A-I, B-II, C-III, D-IV
2. A-II, B-I, C-IV, D-III
3. A-III, B-IV, C-I, D-II
4. A-IV, B-III, C-II, D-I
Answer & Explanation: Option 1. Source exhibits positive hydrostatic pressure, sink has negative pressure, phloem transports sugars, and mass flow is the bulk movement mechanism. This matching highlights pressure-driven movement, vascular tissue function, and the role of source-sink dynamics. Understanding these components is crucial for explaining efficient translocation, nutrient distribution, and plant physiological regulation, emphasizing the integration of hydrostatic forces and transport processes.
9. Fill in the Blanks / Completion MCQ
Mass flow in phloem occurs due to _______ between source and sink.
Options:
A. Concentration gradient
B. Hydrostatic pressure difference
C. Temperature gradient
D. Osmotic equilibrium only
Answer & Explanation: Option B. Mass flow occurs due to hydrostatic pressure differences created by sugar loading at the source and unloading at the sink. This pressure drives bulk sap movement, faster than diffusion. Understanding this mechanism explains long-distance transport, energy allocation, and sink-source interactions. It underpins phloem physiology, plant growth, and distribution of photosynthates to developing tissues, ensuring efficient carbohydrate transport and overall plant health.
10. Choose the Correct Statements MCQ
Statement I: Mass flow is faster than diffusion.
Statement II: Solutes in mass flow move at the same pace.
Options:
A. Both I and II are correct
B. Only I is correct
C. Only II is correct
D. Both I and II are incorrect
Answer & Explanation: Option A. Mass flow is faster than diffusion and all solutes move together at the same pace along the hydrostatic pressure gradient. This mechanism ensures efficient transport of sugars from source to sink. Understanding these statements is essential for plant physiology, phloem translocation, and energy allocation, emphasizing the role of pressure-driven bulk movement in supporting growth, storage, and nutrient distribution across plant tissues.
Keyword Definitions:
Cohesion: Mutual attraction between water molecules due to hydrogen bonding.
Adhesion: Attraction between water molecules and polar surfaces like xylem walls.
Surface tension: The tendency of a liquid surface to resist external force, caused by cohesive forces.
Guttation: Exudation of water droplets from leaf tips or edges through hydathodes.
Hydrogen bonding: Weak interactions between polar molecules responsible for water cohesion and adhesion.
Transpiration: Evaporation of water from aerial parts of plants, different from guttation.
Hydathodes: Specialized leaf structures through which guttation occurs.
Capillarity: Movement of water in narrow tubes due to adhesion and cohesion.
Plant water potential: A measure of potential energy of water in plant tissues driving movement.
Polar surfaces: Surfaces with charges that attract water molecules through adhesion.
Liquid phase: State of water in xylem and plant tissues where cohesion and adhesion act.
Lead Question - 2023:
Match List I with List II:
List - I List - II
A. Cohesion – I. More attraction in liquid phase
B. Adhesion – II. Mutual attraction among water molecules
C. Surface tension – III. Water loss in liquid phase
D. Guttation – IV. Attraction towards polar surfaces
Choose the correct answer:
(1) A-III, B-I, C-IV, D-II
(2) A-II, B-I, C-IV, D-III
(3) A-II, B-IV, C-I, D-III
(4) A-IV, B-III, C-II, D-I
Answer & Explanation: (3) A-II, B-IV, C-I, D-III. Cohesion is the mutual attraction among water molecules (A-II), adhesion is attraction of water molecules to polar surfaces such as xylem walls (B-IV), surface tension arises due to more attraction in the liquid phase at the surface (C-I), and guttation is the process of water loss in liquid form through hydathodes (D-III). These interactions help in water transport and retention in plants. Cohesion and adhesion assist in capillary action, while surface tension maintains water integrity. Guttation occurs mostly at night due to root pressure.
1. Which process results in exudation of water droplets from leaf edges?
(1) Transpiration
(2) Guttation
(3) Evaporation
(4) Condensation
Explanation: Guttation is the process of water exudation in liquid form through hydathodes, typically at night due to root pressure. Correct answer is (2).
2. Cohesion in water is mainly due to:
(1) Covalent bonding
(2) Ionic bonding
(3) Hydrogen bonding
(4) Metallic bonding
Explanation: Cohesion arises from hydrogen bonding between water molecules, enabling water to resist separation. Correct answer is (3).
3. Adhesion helps in:
(1) Water movement through xylem
(2) Photosynthesis
(3) Respiration
(4) Protein synthesis
Explanation: Adhesion causes water molecules to stick to xylem walls, aiding upward movement against gravity. Correct answer is (1).
4. Surface tension is maximum in:
(1) Oil
(2) Water
(3) Alcohol
(4) Acetone
Explanation: Water exhibits high surface tension due to strong cohesion among molecules at the liquid surface. Correct answer is (2).
5. Hydathodes are responsible for:
(1) Photosynthesis
(2) Guttation
(3) Transpiration
(4) Respiration
Explanation: Hydathodes are specialized leaf structures facilitating guttation by releasing liquid water from leaf tips and edges. Correct answer is (2).
6. Root pressure contributes to:
(1) Cohesion
(2) Adhesion
(3) Guttation
(4) Surface tension
Explanation: Root pressure pushes water into xylem, causing guttation at night when transpiration is low. Correct answer is (3).
Assertion-Reason Type Question
7. Assertion (A): Cohesion is essential for water transport in plants.
Reason (R): Cohesion allows water column in xylem to resist breakage during transpiration pull.
(1) Both A and R true, R explains A
(2) Both A and R true, R does not explain A
(3) A true, R false
(4) A false, R true
Explanation: Cohesion maintains continuous water column in xylem, essential for upward transport. R correctly explains A. Correct answer is (1).
Matching Type Question
8. Match the term with definition:
A. Cohesion – i. Attraction to polar surfaces
B. Adhesion – ii. Mutual attraction among water molecules
C. Surface tension – iii. Resistance at water surface
D. Guttation – iv. Exudation of liquid water
(1) A-ii, B-i, C-iii, D-iv
(2) A-i, B-ii, C-iv, D-iii
(3) A-iii, B-iv, C-i, D-ii
(4) A-iv, B-iii, C-ii, D-i
Explanation: Cohesion is mutual attraction (A-ii), adhesion is attraction to polar surfaces (B-i), surface tension is resistance at water surface (C-iii), guttation is exudation of water (D-iv). Correct answer is (1).
Fill in the Blanks Question
9. Water molecules stick to xylem walls due to _______.
(1) Cohesion
(2) Adhesion
(3) Surface tension
(4) Root pressure
Explanation: Adhesion causes water molecules to stick to xylem walls, aiding upward movement. Correct answer is (2).
Choose the Correct Statements Question
10. Statement I: Guttation occurs mainly at night.
Statement II: Transpiration and guttation are identical processes.
(1) Both I and II correct
(2) Only I correct
(3) Only II correct
(4) Neither I nor II correct
Explanation: Guttation occurs at night due to root pressure when stomata are closed (I correct). Transpiration is water loss in vapor form, different from guttation. Correct answer is (2).
Keyword Definitions:
Active Transport: Movement of ions or molecules across a membrane against their concentration gradient using energy, usually from ATP.
Passive Transport: Movement of substances down their concentration gradient without energy expenditure.
Osmosis: Diffusion of water molecules across a selectively permeable membrane.
Facilitated Diffusion: Passive transport of molecules via specific carrier or channel proteins.
Concentration Gradient: Difference in concentration of a substance between two regions.
Ion Pump: Membrane protein that actively transports ions using ATP.
Membrane Potential: Electrical potential difference across a cell membrane.
Endocytosis: Process of internalizing molecules by vesicle formation.
Exocytosis: Secretion of molecules via vesicles fusing with the plasma membrane.
Electrochemical Gradient: Combined concentration and charge gradient driving ion movement.
ATP (Adenosine Triphosphate): Energy currency of the cell used for active transport and other cellular processes.
Lead Question - 2023:
Movement and accumulation of ions across a membrane against their concentration gradient can be explained by:
(1) Passive Transport
(2) Active Transport
(3) Osmosis
(4) Facilitated Diffusion
Answer & Explanation: (2) Active Transport. Active transport involves the movement of ions or molecules against their concentration gradient, requiring energy often derived from ATP. This mechanism allows cells to maintain ion homeostasis, create membrane potentials, and accumulate essential nutrients. Passive transport, osmosis, and facilitated diffusion move substances down their concentration gradients and do not require energy input. Active transport is crucial for functions like Na⁺/K⁺-ATPase operation, proton pumps, and nutrient uptake in plants and animals. It ensures selective accumulation or extrusion of ions for physiological processes, signaling, and maintaining cellular balance.
1. Which transport requires ATP?
(1) Passive Transport
(2) Active Transport
(3) Facilitated Diffusion
(4) Osmosis
Explanation: Active transport uses energy from ATP to move molecules against their concentration gradient, unlike passive transport or facilitated diffusion. Correct answer is (2).
2. Movement of water across a membrane is called:
(1) Active Transport
(2) Osmosis
(3) Facilitated Diffusion
(4) Endocytosis
Explanation: Osmosis is the passive movement of water molecules across a selectively permeable membrane. Correct answer is (2).
3. Sodium-potassium pump is an example of:
(1) Passive Transport
(2) Active Transport
(3) Osmosis
(4) Facilitated Diffusion
Explanation: Na⁺/K⁺-ATPase moves sodium and potassium ions against their gradients using ATP. Correct answer is (2).
4. Which transport moves substances down their concentration gradient?
(1) Active Transport
(2) Facilitated Diffusion
(3) Endocytosis
(4) Exocytosis
Explanation: Facilitated diffusion moves molecules passively down their concentration gradient via carrier proteins. Correct answer is (2).
5. Proton pump is used to:
(1) Pump H⁺ ions against gradient
(2) Transport water
(3) Passive ion movement
(4) Facilitate diffusion
Explanation: Proton pumps actively move H⁺ ions against their electrochemical gradient using energy from ATP. Correct answer is (1).
6. Electrochemical gradient is important for:
(1) Active transport
(2) Osmosis
(3) Facilitated diffusion
(4) Lipid synthesis
Explanation: Electrochemical gradients drive active transport of ions across membranes, combining concentration and electrical differences. Correct answer is (1).
Assertion-Reason Type Question
7. Assertion (A): Active transport moves molecules against the gradient.
Reason (R): It requires energy from ATP or other sources.
(1) Both A and R are true and R is the correct explanation of A
(2) Both A and R are true but R is not the correct explanation of A
(3) A is true, R is false
(4) A is false, R is true
Explanation: Active transport requires energy to move molecules against concentration or electrochemical gradients. Both statements are true, and R correctly explains A. Correct answer is (1).
Matching Type Question
8. Match the transport type with description:
A. Active Transport – (i) Moves against concentration gradient using energy
B. Osmosis – (ii) Passive water movement
C. Facilitated Diffusion – (iii) Passive movement via proteins
D. Passive Transport – (iv) Movement down concentration gradient
(1) A-(i), B-(ii), C-(iii), D-(iv)
(2) A-(ii), B-(i), C-(iv), D-(iii)
(3) A-(i), B-(iii), C-(ii), D-(iv)
(4) A-(iv), B-(ii), C-(iii), D-(i)
Explanation: Active transport requires energy to move molecules against gradients; osmosis and facilitated diffusion are passive. Correct answer is (1).
Fill in the Blanks Question
9. Transport of ions using ATP against a gradient is called _______.
(1) Passive Transport
(2) Active Transport
(3) Osmosis
(4) Facilitated Diffusion
Explanation: Movement against a concentration gradient using energy is active transport. Correct answer is (2).
Choose the Correct Statements Question
10. Statement I: Active transport requires energy.
Statement II: Passive transport moves molecules down the gradient.
(1) Both statements are true
(2) Statement I true, Statement II false
(3) Statement I false, Statement II true
(4) Both statements are false
Explanation: Active transport consumes energy, while passive transport moves substances down their concentration gradient. Both statements are correct. Correct answer is (1).
Keyword Definitions:
Transpiration: Loss of water vapor from aerial parts of plants, mainly through stomata.
Xylem: Tissue responsible for the transport of water and minerals from roots to leaves.
Cohesion-Tension Theory: Explains the upward movement of water in plants due to cohesive and adhesive forces.
Evaporative Cooling: Process by which evaporation of water from leaf surfaces lowers their temperature.
Transpirational Pull: The negative pressure created in xylem due to water loss that pulls water upward.
Lead Question - 2023
Given below are two statements:
Statement I: The forces generated by transpiration can lift a xylem-sized column of water over 130 meters height.
Statement II: Transpiration cools leaf surfaces sometimes 10 to 15 degrees, by evaporative cooling.
In the light of the above statements, choose the most appropriate answer from the options given below:
(1) Statement I is correct but Statement II is incorrect
(2) Statement II is incorrect but Statement I is correct
(3) Both Statement I and Statement II are correct
(4) Both Statement I and Statement II are incorrect
Answer & Explanation: (3) Both Statement I and Statement II are correct. Transpiration generates a negative pressure that helps lift water columns in tall trees, demonstrating the power of transpirational pull. Additionally, the evaporation of water from leaf surfaces removes latent heat, cooling leaves by up to 10–15°C, aiding in temperature regulation and enzyme protection.
1. Which of the following structures directly facilitate transpiration?
(1) Stomata
(2) Phloem
(3) Cortex
(4) Endodermis
Answer & Explanation: (1) Stomata. Transpiration mainly occurs through stomata, small pores in the leaf epidermis that regulate gas exchange and water vapor loss. Their opening and closing depend on light, humidity, and internal water status, thus maintaining water balance and nutrient flow through the plant.
2. In tall trees, the main force responsible for upward movement of water is:
(1) Root pressure
(2) Capillarity
(3) Transpirational pull
(4) Active transport
Answer & Explanation: (3) Transpirational pull. The loss of water from leaves creates a negative pressure in xylem that draws water upward from roots through cohesion and adhesion forces. This passive mechanism maintains water transport over long distances in tall trees efficiently.
3. Root pressure is maximum during:
(1) Daytime with high transpiration
(2) Nighttime with low transpiration
(3) Morning hours
(4) Drought periods
Answer & Explanation: (2) Nighttime with low transpiration. Root pressure develops when transpiration is minimal, usually at night, pushing water into xylem vessels. It helps re-establish continuous water columns and may cause guttation in some plants through leaf margins.
4. The process of guttation occurs through:
(1) Lenticels
(2) Hydathodes
(3) Stomata
(4) Cuticle
Answer & Explanation: (2) Hydathodes. Guttation involves exudation of liquid water from leaf tips or edges through specialized openings called hydathodes, usually when root pressure is high and transpiration is low, maintaining xylem water continuity in small plants.
5. Water potential in a leaf during transpiration is:
(1) Higher than in roots
(2) Equal to roots
(3) Lower than in roots
(4) Same as soil
Answer & Explanation: (3) Lower than in roots. During transpiration, water evaporates from leaf mesophyll cells, reducing water potential and creating a gradient from roots to leaves. This gradient drives water movement upward through xylem by cohesion-tension forces.
6. The cohesion-tension theory of water transport was proposed by:
(1) Dixon and Joly
(2) Strasburger
(3) Mohl
(4) Priestley
Answer & Explanation: (1) Dixon and Joly. In 1894, they proposed that water is pulled upward in xylem due to cohesion between water molecules and adhesion with vessel walls, forming a continuous column under negative pressure generated by transpiration from leaves.
7. (Assertion-Reason Type)
Assertion (A): Transpiration results in the ascent of sap.
Reason (R): It creates a negative pressure in xylem facilitating upward water movement.
(1) Both A and R are true, and R is the correct explanation of A.
(2) Both A and R are true, but R is not the correct explanation of A.
(3) A is true, but R is false.
(4) A is false, but R is true.
Answer & Explanation: (1) Both A and R are true, and R explains A. Transpiration generates tension in leaf xylem, pulling water upward as a continuous column, establishing the ascent of sap due to cohesive and adhesive water properties within xylem vessels.
8. (Matching Type)
Match the column:
A. Stomatal transpiration — (i) Major type of transpiration
B. Cuticular transpiration — (ii) Through leaf surface
C. Lenticular transpiration — (iii) Through bark openings
(1) A–i, B–ii, C–iii
(2) A–ii, B–i, C–iii
(3) A–i, B–iii, C–ii
(4) A–iii, B–i, C–ii
Answer & Explanation: (1) A–i, B–ii, C–iii. Stomatal transpiration is the main pathway through leaf stomata, cuticular transpiration occurs through the leaf cuticle, and lenticular transpiration takes place via lenticels in woody stems, contributing minimally to total water loss.
9. (Fill in the Blanks)
__________ theory explains water ascent due to cohesive and adhesive forces along with transpirational pull.
(1) Pressure-flow
(2) Cohesion-tension
(3) Imbibition
(4) Root pressure
Answer & Explanation: (2) Cohesion-tension. This theory describes how water is pulled upward in xylem as a continuous column due to cohesive forces between molecules and adhesive attraction to vessel walls, sustained by transpirational water loss from leaves.
10. (Choose the Correct Statements Type)
Statement I: Transpiration causes wilting in extreme water loss.
Statement II: Transpiration helps in mineral transport and cooling.
(1) Both statements are correct.
(2) Both statements are incorrect.
(3) Statement I is correct, II is incorrect.
(4) Statement I is incorrect, II is correct.
Answer & Explanation: (1) Both statements are correct. Though excessive transpiration leads to wilting due to water deficit, it plays vital physiological roles—facilitating upward transport of minerals, maintaining temperature balance, and supporting photosynthesis through regulated gas exchange and water flow.
Keyword Definitions:
Transpiration: The process of water loss in the form of vapour from aerial parts of plants, mainly through stomata.
Xylem: A vascular tissue responsible for transport of water and minerals from roots to other parts of the plant.
Cohesion-Tension Theory: Explains upward movement of water through xylem due to cohesion between water molecules and transpiration pull.
Evaporative Cooling: The cooling effect produced when water evaporates from leaf surfaces, reducing leaf temperature.
Ascent of Sap: The upward flow of water and dissolved minerals from roots to leaves through the xylem vessels.
Lead Question (2023): Given below are two statements:
Statement I: The forces generated by transpiration can lift a xylem-sized column of water over 130 meters height.
Statement II: Transpiration cools leaf surfaces sometimes 10 to 15 degrees, by evaporative cooling.
In the light of the above statements choose the most appropriate answer from the options given below:
(1) Statement I is correct but Statement II is incorrect
(2) Statement II is incorrect but Statement I is correct
(3) Both Statement I and Statement II are correct
(4) Both Statement I and Statement II are incorrect
Answer & Explanation: (3) Both Statement I and Statement II are correct. Transpiration creates a strong negative pressure that helps pull water up through the xylem even to great heights, such as in tall trees. It also results in evaporative cooling, which reduces leaf temperature by 10–15°C, preventing overheating and maintaining optimal physiological activity for photosynthesis and enzyme functioning.
Guessed Questions:
1. The major force responsible for movement of water in xylem during transpiration is:
(1) Root pressure
(2) Capillary action
(3) Transpiration pull
(4) Active transport
Answer & Explanation: (3) Transpiration pull. The evaporation of water from mesophyll cells generates a negative pressure in the leaf xylem. This pull, transmitted down the continuous water column, helps lift water from roots to leaves. Cohesion among water molecules and adhesion to xylem walls maintain column stability against gravity.
2. The ascent of sap in tall trees can be explained by:
(1) Capillary force
(2) Root pressure only
(3) Cohesion-tension theory
(4) Diffusion of water molecules
Answer & Explanation: (3) Cohesion-tension theory. This theory explains that water molecules stick together (cohesion) and adhere to xylem walls (adhesion). The continuous water column is pulled upward by tension created through transpiration at the leaf surface. It accounts for the remarkable height water reaches in tall trees.
3. Which of the following statements regarding transpiration is true?
(1) It increases leaf temperature
(2) It causes wilting
(3) It aids in nutrient transport and cooling
(4) It decreases water absorption
Answer & Explanation: (3) It aids in nutrient transport and cooling. Transpiration not only drives the ascent of sap but also helps maintain temperature balance through evaporative cooling. This cooling effect prevents heat stress, while continuous water movement ensures mineral transport and photosynthetic efficiency in green tissues.
4. Root pressure alone cannot explain water movement in tall trees because:
(1) It is too weak to lift water beyond a few meters
(2) It acts only during transpiration
(3) It causes cavitation
(4) It depends on photosynthesis
Answer & Explanation: (1) It is too weak to lift water beyond a few meters. Root pressure results from osmotic flow of water into xylem, generating positive pressure. However, in tall trees, this pressure is insufficient, and transpiration pull through cohesion-tension mechanism is the major driving force for upward water transport.
5. Which component of xylem is mainly responsible for long-distance transport of water?
(1) Xylem fibers
(2) Xylem parenchyma
(3) Vessels and tracheids
(4) Companion cells
Answer & Explanation: (3) Vessels and tracheids. These are elongated dead cells forming continuous tubular structures that facilitate water conduction under tension. Their lignified walls provide mechanical support and prevent collapse under negative pressure generated during transpiration pull, ensuring efficient long-distance water movement in vascular plants.
6. The cooling effect due to transpiration in leaves helps in:
(1) Increasing stomatal opening
(2) Preventing enzyme denaturation
(3) Increasing transpiration rate
(4) Reducing turgor pressure
Answer & Explanation: (2) Preventing enzyme denaturation. Evaporative cooling from transpiration lowers leaf surface temperature, maintaining an optimal range for metabolic and enzymatic processes. This temperature control protects chloroplasts from thermal stress and ensures efficient photosynthesis, particularly under high light or heat conditions in the growing environment.
7. Assertion-Reason Type:
Assertion (A): Water column in xylem does not break under tension.
Reason (R): Cohesive and adhesive forces maintain water continuity.
(1) Both A and R are true, and R is the correct explanation of A
(2) Both A and R are true, but R is not the correct explanation of A
(3) A is true but R is false
(4) A is false but R is true
Answer & Explanation: (1) Both A and R are true, and R is the correct explanation of A. Cohesion between water molecules and adhesion to xylem walls maintain the continuous water column, even under high tension during transpiration. These forces ensure uninterrupted water movement without cavitation in tall plants.
8. Matching Type Question:
Match the following structures with their functions:
A. Stomata
B. Xylem vessels
C. Cuticle
D. Root hair
(1) A–Water loss, B–Conduction, C–Prevention of water loss, D–Absorption
(2) A–Conduction, B–Water loss, C–Absorption, D–Support
(3) A–Support, B–Absorption, C–Conduction, D–Protection
(4) A–Storage, B–Transport, C–Evaporation, D–Protection
Answer & Explanation: (1) A–Water loss, B–Conduction, C–Prevention of water loss, D–Absorption. Stomata control water loss through transpiration, xylem conducts water, the cuticle minimizes evaporation, and root hairs absorb water from soil, collectively maintaining water balance and efficient transport in plants.
9. Fill in the Blanks:
The main negative pressure responsible for upward movement of water is called __________.
(1) Root pressure
(2) Osmotic pull
(3) Transpiration pull
(4) Capillary rise
Answer & Explanation: (3) Transpiration pull. Evaporation of water from leaf cells during transpiration creates negative pressure within xylem. This pressure draws water upwards, maintaining the continuous column of water from roots to leaves. The process is vital for maintaining hydration and nutrient transport throughout the plant body.
10. Choose the Correct Statements (Statement I & II):
Statement I: Transpiration assists in absorption and upward movement of water.
Statement II: Transpiration causes overheating of leaf surfaces.
(1) Both statements are correct
(2) Both statements are incorrect
(3) Statement I is correct, Statement II is incorrect
(4) Statement I is incorrect, Statement II is correct
Answer & Explanation: (3) Statement I is correct, Statement II is incorrect. Transpiration promotes water absorption through transpiration pull and helps in cooling leaf surfaces via evaporation. It does not cause overheating; instead, it regulates plant temperature and supports mineral uptake and physiological functions necessary for survival and growth.
Topic: Membrane Structure and Function; Subtopic: Permeability and Transport Mechanisms
Keyword Definitions:
• Cell membrane: Semi-permeable lipid bilayer enclosing the cell, controlling entry and exit of substances.
• Hydrophobic moiety: Non-polar chemical group that repels water and is lipid-soluble.
• Hydrophilic moiety: Polar chemical group that interacts with water and is water-soluble.
• Lipid-soluble substances: Molecules that dissolve easily in lipids and pass through membranes.
• Permeability: The property of a membrane to allow substances to pass.
• Passive transport: Movement of molecules along concentration gradient without energy.
• Active transport: Energy-requiring movement of molecules against the concentration gradient.
• Semi-permeable: Allows selective passage of certain molecules.
• Transport proteins: Proteins that assist in moving substances across membranes.
• Diffusion: Movement of molecules from high to low concentration.
• Membrane barrier: The hydrophobic core of the lipid bilayer that impedes polar molecules.
Lead Question - 2022 (Ganganagar)
Which type of substance would face difficulty to pass through the cell membrane?
1. Substance with hydrophobic moiety
2. Substance with hydrophilic moiety
3. All substance irrespective of hydrophobic and hydrophilic moiety
4. Substance soluble in lipids
Explanation: The cell membrane's hydrophobic lipid bilayer allows lipid-soluble substances and hydrophobic molecules to pass easily, while polar or hydrophilic molecules face difficulty due to the non-polar core. Such substances often require transport proteins or channels to cross. Therefore, molecules with hydrophilic moieties cannot readily diffuse through the membrane. Correct answer is 2. The selective permeability of the membrane ensures efficient cellular regulation, with transport mechanisms compensating for hydrophilic molecule transport, maintaining homeostasis, and supporting essential metabolic processes within the cell.
1. Single Correct Answer MCQ:
Which molecule type diffuses most easily across the lipid bilayer?
a) Hydrophilic molecules
b) Hydrophobic molecules
c) Ions
d) Polar macromolecules
Explanation: Hydrophobic molecules dissolve in the lipid bilayer and diffuse easily without assistance. Correct answer is b) Hydrophobic molecules.
2. Single Correct Answer MCQ:
Which factor restricts hydrophilic molecules from passing through membranes?
a) Lipid bilayer's non-polar core
b) Presence of water channels
c) Transport proteins
d) Membrane fluidity
Explanation: Hydrophilic molecules are repelled by the non-polar lipid core, restricting passive diffusion. Correct answer is a) Lipid bilayer's non-polar core.
3. Single Correct Answer MCQ:
Transport proteins are mainly required for:
a) Lipid-soluble molecules
b) Hydrophobic molecules
c) Hydrophilic molecules
d) Non-polar gases
Explanation: Hydrophilic molecules require channels or carrier proteins to cross the hydrophobic membrane efficiently. Correct answer is c) Hydrophilic molecules.
4. Single Correct Answer MCQ:
Which molecule passes freely through membranes without protein assistance?
a) Glucose
b) Sodium ion
c) Oxygen
d) Amino acids
Explanation: Non-polar molecules like oxygen diffuse freely through the hydrophobic core of the membrane. Correct answer is c) Oxygen.
5. Single Correct Answer MCQ:
Ions face difficulty crossing membranes because:
a) They are hydrophobic
b) They are charged
c) Membranes have pores
d) Membranes are fluid
Explanation: Charged ions cannot easily pass the non-polar membrane core without channels or pumps. Correct answer is b) They are charged.
6. Single Correct Answer MCQ:
Which substance is least likely to require facilitated transport?
a) Water
b) Sodium
c) Glucose
d) Oxygen
Explanation: Oxygen, being non-polar, diffuses freely across the lipid bilayer without assistance. Correct answer is d) Oxygen.
7. Assertion-Reason MCQ:
Assertion (A): Hydrophilic molecules cannot easily diffuse through the cell membrane.
Reason (R): The cell membrane has a hydrophobic lipid bilayer.
a) Both A and R true, R explains A
b) Both A and R true, R does not explain A
c) A true, R false
d) A false, R true
Explanation: The hydrophobic core repels polar hydrophilic molecules, restricting passive diffusion. Correct answer is a) Both A and R true, R explains A.
8. Matching Type MCQ:
Match molecules with their membrane passage mode:
Column I | Column II
A) Hydrophobic | 1) Free diffusion
B) Hydrophilic | 2) Facilitated transport
C) Ion | 3) Requires channels
D) Lipid-soluble | 4) Free diffusion
Choices: A-__ B-__ C-__ D-__
Explanation: Hydrophobic and lipid-soluble molecules cross via free diffusion (A-1, D-4), hydrophilic molecules require facilitated transport (B-2), ions require specific channels (C-3).
9. Fill in the Blanks / Completion MCQ:
Substances with hydrophilic moieties often require ______ to cross the cell membrane.
a) Simple diffusion
b) Facilitated transport
c) Osmosis
d) Active pumping
Explanation: Hydrophilic molecules cannot pass the hydrophobic membrane easily and need facilitated transport through proteins. Correct answer is b) Facilitated transport.
10. Choose the correct statements MCQ (Statement I & II):
Statement I: Hydrophobic molecules pass easily through cell membranes.
Statement II: Hydrophilic molecules can freely diffuse across lipid bilayers.
a) Both correct
b) Only I correct
c) Only II correct
d) Both incorrect
Explanation: Hydrophobic molecules cross freely due to membrane solubility, whereas hydrophilic molecules face difficulty. Only Statement I is correct. Correct answer is b) Only I correct.
Topic: Transport in Plants; Subtopic: Ascent of Sap and Water Transport Mechanisms
Keyword Definitions:
• Xylem sap: Water and dissolved minerals transported from roots to aerial parts of plants through xylem vessels.
• Ascent of xylem sap: Upward movement of water from roots to leaves against gravity.
• Cohesion: Attraction between water molecules due to hydrogen bonding.
• Adhesion: Attraction between water molecules and xylem vessel walls.
• Root pressure: Osmotically generated pressure in roots pushing water upward.
• Stomatal aperture: Opening of stomata controlling transpiration and gas exchange.
• Distribution of stomata: Location and density of stomata on leaf surfaces affecting transpiration rate.
• Transpiration pull: Suction force created by water loss from leaves that pulls xylem sap upward.
• Water potential: Potential energy of water influencing its movement within plant tissues.
• Vascular tissue: Plant tissue, including xylem and phloem, responsible for water and nutrient transport.
• Hydraulic continuity: Continuous water column maintained in xylem vessels through cohesion and adhesion.
Lead Question - 2022 (Ganganagar)
The ascent of xylem sap in plants is mainly accomplished by the:
1. Size of the stomatal aperture
2. Distribution of stomata on the upper and lower epidermis
3. Cohesion and adhesion between water molecules
4. Root pressure
Explanation: The primary mechanism for ascent of xylem sap is cohesion-tension theory, where water molecules stick to each other (cohesion) and to xylem walls (adhesion), forming a continuous column. Transpiration from leaves generates a negative pressure that pulls water upward. Root pressure and stomatal features assist but are minor contributors. Therefore, the correct answer is 3. Cohesion and adhesion between water molecules. This mechanism ensures continuous water supply to leaves, supporting photosynthesis, nutrient transport, and plant growth, particularly in tall trees where root pressure alone cannot account for sap ascent.
1. Single Correct Answer MCQ:
Transpiration pull in xylem is generated due to:
a) Water evaporation from mesophyll cells
b) Photosynthesis in chloroplasts
c) Soil water absorption
d) Guard cell expansion
Explanation: Transpiration pull arises when water evaporates from mesophyll cell walls into the air spaces of leaves, creating negative pressure in xylem. This pulls water upward from roots through cohesive and adhesive forces. Photosynthesis, soil water absorption, and guard cell expansion are not direct drivers. Correct answer is a) Water evaporation from mesophyll cells.
2. Single Correct Answer MCQ:
Root pressure is most effective in:
a) Tall trees
b) Herbaceous plants
c) Desert shrubs
d) Aquatic plants
Explanation: Root pressure, generated osmotically by ion accumulation in roots, can push water upward but is usually sufficient only in small herbaceous plants. In tall trees, transpiration pull dominates. Correct answer is b) Herbaceous plants.
3. Single Correct Answer MCQ:
Cohesion between water molecules is due to:
a) Ionic bonds
b) Covalent bonds
c) Hydrogen bonds
d) Van der Waals forces
Explanation: Cohesion in water arises from hydrogen bonds between molecules, allowing formation of a continuous column in xylem vessels. Ionic or covalent bonds exist within molecules, not between them. Van der Waals forces are weak and do not account for sap ascent. Correct answer is c) Hydrogen bonds.
4. Single Correct Answer MCQ:
Adhesion of water molecules helps in:
a) Reducing transpiration
b) Sticking water to xylem walls
c) Photosynthesis
d) Root growth
Explanation: Adhesion allows water molecules to cling to hydrophilic xylem walls, supporting the continuous column necessary for ascent. This complements cohesion and prevents cavitation. It does not directly reduce transpiration, aid photosynthesis, or stimulate root growth. Correct answer is b) Sticking water to xylem walls.
5. Single Correct Answer MCQ:
Which plant adaptation helps maximize transpiration pull?
a) Thick cuticle
b) Large number of xylem vessels
c) Low stomatal density
d) Reduced leaf area
Explanation: A large number of xylem vessels ensures efficient water transport, supporting strong transpiration pull and preventing embolism. Thick cuticle or reduced leaves minimize water loss, not pull. Low stomatal density reduces transpiration. Correct answer is b) Large number of xylem vessels.
6. Single Correct Answer MCQ:
Which factor has minimal role in the ascent of xylem sap?
a) Cohesion and adhesion
b) Transpiration pull
c) Root pressure
d) Capillarity
Explanation: While root pressure and capillarity contribute, their effect is minor in tall plants. Transpiration pull mediated by cohesion and adhesion is the dominant mechanism. Correct answer is c) Root pressure.
7. Assertion-Reason MCQ:
Assertion (A): Transpiration pull is the major driving force for xylem sap ascent.
Reason (R): Water molecules exhibit cohesion and adhesion, maintaining a continuous column in xylem.
a) Both A and R are true, R explains A
b) Both A and R are true, R does not explain A
c) A is true, R is false
d) A is false, R is true
Explanation: Transpiration creates negative pressure, pulling water upward, while cohesion and adhesion maintain the water column. Both statements are true and the reason explains the mechanism of ascent. Correct answer is a) Both A and R are true, R explains A.
8. Matching Type MCQ:
Match the term with its role in water transport:
Column I
A) Cohesion
B) Adhesion
C) Root pressure
D) Transpiration
Column II
1) Maintains continuous water column
2) Pulls water upward from roots
3) Clings water to xylem walls
4) Generates osmotic push in small plants
Choices:
A-__ B-__ C-__ D-__
Explanation: Cohesion maintains water continuity (A-1), adhesion sticks water to walls (B-3), root pressure pushes water in small plants (C-4), and transpiration creates pull (D-2). Correct matches: A-1, B-3, C-4, D-2.
9. Fill in the Blanks / Completion MCQ:
The cohesion-tension theory explains __________ of xylem sap.
a) Lateral movement
b) Upward movement
c) Storage in roots
d) Leaf transpiration only
Explanation: Cohesion-tension theory describes upward movement of water from roots to leaves via continuous water column maintained by cohesion and adhesion, driven by transpiration pull. It does not explain lateral movement or storage. Correct answer is b) Upward movement.
10. Choose the correct statements MCQ (Statement I & II):
Statement I: Cohesion and adhesion are essential for ascent of sap.
Statement II: Root pressure alone can drive sap to the top of tall trees.
a) Both I and II are correct
b) Only I is correct
c) Only II is correct
d) Both are incorrect
Explanation: Cohesion and adhesion maintain a continuous water column essential for transpiration pull. Root pressure is minor and cannot move water to tree tops. Statement I is correct, Statement II is false. Correct answer is b) Only I is correct.
Topic: Membrane Transport; Subtopic: Carrier Proteins and Transport Mechanisms
Keyword Definitions:
• Carrier protein: Membrane protein that binds and transports specific molecules across the lipid bilayer.
• Uniport: Transport of a single molecule or ion across a membrane in one direction.
• Symport: Transport of two different molecules simultaneously in the same direction across a membrane.
• Antiport: Transport of two different molecules in opposite directions across a membrane.
• Transport: General movement of substances across membranes, can be passive or active.
• Active transport: Movement of molecules against their concentration gradient, requiring energy.
• Passive transport: Movement of molecules down their concentration gradient without energy.
• Concentration gradient: Difference in solute concentration across a membrane.
• Facilitated diffusion: Passive transport mediated by carrier or channel proteins.
• Membrane: Lipid bilayer that separates intracellular and extracellular environments.
• Molecule: Chemical entity transported across membranes, such as ions, sugars, or amino acids.
Lead Question - 2022 (Ganganagar)
When a carrier protein facilitates the movement of two molecules across the membrane in same direction, it is called:
1. Uniport
2. Transport
3. Antiport
4. Symport
Explanation: When two molecules are transported simultaneously in the same direction across a membrane via a carrier protein, the process is called symport. Uniport transports a single molecule, antiport moves two molecules in opposite directions, and transport is a general term. Symporters couple the movement of one molecule down its gradient to drive the transport of another, often essential for nutrient uptake or ion balance. Hence, the correct answer is 4. Symport. This coordinated transport is crucial in maintaining cellular homeostasis and energy efficiency across membranes.
1. Single Correct Answer MCQ:
Which of the following is an example of symport?
a) Sodium-glucose transporter
b) Sodium-potassium pump
c) GLUT1
d) Aquaporin
Explanation: Sodium-glucose transporters move glucose and sodium ions together into cells, exemplifying symport. Sodium-potassium pump is an antiporter, GLUT1 is a uniporter for glucose, and aquaporins facilitate water movement. Symport couples ion gradient to drive uptake. Correct answer is a) Sodium-glucose transporter.
2. Single Correct Answer MCQ:
Antiport is defined as:
a) Transport of a single molecule
b) Transport of two molecules in same direction
c) Transport of two molecules in opposite directions
d) Passive diffusion
Explanation: Antiport involves movement of two molecules in opposite directions across the membrane. Uniport moves one molecule, symport moves two in same direction, and passive diffusion does not require carrier proteins. Antiporters maintain ion gradients and cellular homeostasis. Correct answer is c) Transport of two molecules in opposite directions.
3. Single Correct Answer MCQ:
Which type of transport does not require energy?
a) Passive transport
b) Active transport
c) Symport
d) Antiport
Explanation: Passive transport moves molecules down their concentration gradient without energy, either by diffusion or facilitated diffusion. Active transport requires ATP or ion gradients, symport and antiport can be secondary active transport. Correct answer is a) Passive transport.
4. Single Correct Answer MCQ:
Uniport carriers transport:
a) Two molecules in opposite directions
b) One molecule in one direction
c) Two molecules in same direction
d) Water only
Explanation: Uniport carriers transport a single molecule across the membrane in one direction. Symport moves two molecules together, antiport moves two in opposite directions, and aquaporins specifically transport water. Correct answer is b) One molecule in one direction.
5. Single Correct Answer MCQ:
The sodium-potassium pump is an example of:
a) Symport
b) Uniport
c) Antiport
d) Facilitated diffusion
Explanation: Sodium-potassium pump moves Na⁺ out of cells and K⁺ in, in opposite directions, using ATP. This is a classic antiporter example. Symport moves molecules together, uniport transports one molecule, and facilitated diffusion is passive. Correct answer is c) Antiport.
6. Single Correct Answer MCQ:
Facilitated diffusion occurs via:
a) Carrier proteins
b) Channel proteins
c) Both carrier and channel proteins
d) Neither
Explanation: Facilitated diffusion is a passive process where specific molecules move down their concentration gradient through carrier or channel proteins. It does not require energy but depends on protein specificity. Both carriers (uniport, symport, antiport) and channels facilitate diffusion. Correct answer is c) Both carrier and channel proteins.
7. Assertion-Reason MCQ:
Assertion (A): Symporters transport two molecules simultaneously in the same direction.
Reason (R): They use the concentration gradient of one molecule to drive the transport of the other.
a) Both A and R are true, R explains A
b) Both A and R are true, R does not explain A
c) A is true, R is false
d) A is false, R is true
Explanation: Symporters move two molecules in the same direction, often using the downhill movement of one molecule (like Na⁺) to drive the uphill transport of another (like glucose). Both statements are true, and the reason explains the mechanism. Correct answer is a) Both A and R are true, R explains A.
8. Matching Type MCQ:
Match the transport type with its characteristic:
Column I
A) Uniport
B) Symport
C) Antiport
D) Passive diffusion
Column II
1) Moves one molecule
2) Moves two molecules in same direction
3) Moves two molecules in opposite directions
4) Moves molecules down gradient without energy
Choices:
A-__ B-__ C-__ D-__
Explanation: Uniport transports one molecule (A-1), symport moves two in same direction (B-2), antiport moves two in opposite directions (C-3), and passive diffusion occurs down gradient without energy (D-4). Correct matches: A-1, B-2, C-3, D-4. This categorization clarifies membrane transport mechanisms.
9. Fill in the Blanks / Completion MCQ:
The movement of glucose with sodium ions into the cell is an example of __________.
a) Antiport
b) Symport
c) Uniport
d) Passive diffusion
Explanation: Sodium-glucose transport couples glucose import with Na⁺ moving down its concentration gradient, transporting both molecules in the same direction. This is a classical example of symport, critical for nutrient absorption in intestines and kidneys. Antiport moves molecules oppositely, uniport moves one molecule, and passive diffusion is gradient-dependent. Correct answer is b) Symport.
10. Choose the correct statements MCQ (Statement I & II):
Statement I: Symport transports two molecules in same direction.
Statement II: Antiport transports two molecules in opposite directions.
a) Both I and II are correct
b) Only I is correct
c) Only II is correct
d) Both are incorrect
Explanation: Symporters move two molecules together in the same direction, while antiporters move two molecules in opposite directions. Both statements accurately describe carrier protein functions in membrane transport, illustrating the mechanisms of secondary active transport. Correct answer is a) Both I and II are correct.
Topic: Amphibolic Pathway and Energy Metabolism ; Subtopic: Role of Porins, Leghemoglobin, and H+ Accumulation
Keyword Definitions:
Porins: Large protein channels present in the outer membrane of mitochondria that allow free movement of small molecules like ions and metabolites.
Leghemoglobin: An oxygen-binding pigment found in root nodules of leguminous plants that facilitates oxygen supply to nitrogen-fixing bacteria.
Thylakoid: Membranous sacs in chloroplasts where light-dependent reactions occur, leading to H+ accumulation inside their lumen.
Amphibolic Pathway: A biochemical pathway that functions both catabolically and anabolically, like the Krebs cycle in respiration.
Respiration: A cellular process that converts biochemical energy from nutrients into ATP, involving glycolysis, Krebs cycle, and electron transport chain.
Lead Question – 2022 (Ganganagar)
Match List-I with List-II:
List-I List-II
(a) Porins (i) Pink coloured nodules
(b) Leghemoglobin (ii) Lumen of thylakoid
(c) H+ Accumulation (iii) Amphibolic pathway
(d) Respiration (iv) Huge pores in outer membrane of mitochondria
Choose the correct answer from the options given below:
(a) (b) (c) (d)
1. (ii) (i) (iv) (iii)
2. (iv) (i) (ii) (iii)
3. (iii) (iv) (ii) (i)
4. (ii) (iv) (i) (iii)
Explanation:
The correct answer is option 2: (a)–(iv), (b)–(i), (c)–(ii), (d)–(iii). Porins are large protein pores in the outer mitochondrial membrane allowing metabolite transport. Leghemoglobin is a pink pigment in root nodules aiding nitrogen fixation. H+ accumulation occurs in thylakoid lumen during photosynthesis, and respiration is an amphibolic pathway involving both energy release and biosynthesis.
1. Single Correct Answer Type
Porins are mainly present in which organelle of eukaryotic cells?
1. Chloroplast
2. Mitochondrion
3. Nucleus
4. Ribosome
Explanation: Porins are large protein channels found in the outer mitochondrial membrane, allowing free passage of small metabolites like ATP, ADP, and ions. They maintain exchange between the cytosol and mitochondria, supporting respiration and energy metabolism. Thus, option 2 is correct, as mitochondria contain porins for efficient transport regulation.
2. Single Correct Answer Type
Leghemoglobin plays an important role in nitrogen fixation by:
1. Releasing oxygen to bacteria
2. Preventing oxygen poisoning of nitrogenase
3. Acting as a carbon source
4. Providing ATP for nitrogenase
Explanation: Leghemoglobin binds oxygen, maintaining a low but steady oxygen concentration inside root nodules. This prevents oxygen inhibition of nitrogenase enzyme while ensuring respiratory ATP synthesis for nitrogen fixation. Hence, option 2 is correct, as leghemoglobin acts as an oxygen buffer promoting efficient nitrogen fixation in legumes.
3. Single Correct Answer Type
H+ accumulation in the lumen of thylakoids occurs during:
1. Glycolysis
2. Light-dependent reactions
3. Calvin cycle
4. Photorespiration
Explanation: During light-dependent reactions of photosynthesis, protons (H+) accumulate inside the thylakoid lumen due to water splitting and electron transport chain activity. This proton gradient drives ATP synthesis through ATP synthase in photophosphorylation. Hence, option 2 is correct as it explains proton motive force formation during photosynthetic reactions.
4. Single Correct Answer Type
Which of the following statements about respiration is true?
1. It is only a catabolic process.
2. It produces ATP without oxidation.
3. It is an amphibolic process.
4. It occurs only in plants.
Explanation: Respiration is an amphibolic process as it functions both catabolically (breaking down glucose to release energy) and anabolically (providing intermediates for biosynthesis). The Krebs cycle acts as a central link between metabolism and biosynthesis. Hence, option 3 is correct as respiration integrates both anabolic and catabolic roles.
5. Single Correct Answer Type
The pink color of root nodules in leguminous plants is due to:
1. Anthocyanin
2. Chlorophyll
3. Leghemoglobin
4. Carotenoid
Explanation: Leghemoglobin, a red-colored oxygen-binding protein similar to animal hemoglobin, imparts a pink coloration to root nodules in leguminous plants. It regulates oxygen supply to nitrogen-fixing bacteria, preventing nitrogenase inactivation. Thus, option 3 is correct as leghemoglobin plays a dual role in oxygen management and symbiotic nitrogen fixation.
6. Single Correct Answer Type
Which of the following is known as the site of oxidative phosphorylation?
1. Thylakoid membrane
2. Mitochondrial inner membrane
3. Cytoplasm
4. Nuclear envelope
Explanation: Oxidative phosphorylation occurs on the inner mitochondrial membrane, where the electron transport chain operates to generate ATP. The proton gradient across this membrane drives ATP synthesis via ATP synthase. Therefore, option 2 is correct, representing mitochondria as the powerhouse of the cell responsible for energy production.
7. Assertion-Reason Type
Assertion (A): Respiration is both a catabolic and anabolic pathway.
Reason (R): Intermediates of the Krebs cycle participate in biosynthesis of amino acids and fats.
1. Both (A) and (R) are correct and (R) explains (A).
2. Both (A) and (R) are correct but (R) does not explain (A).
3. (A) is correct but (R) is incorrect.
4. (A) is incorrect but (R) is correct.
Explanation: Respiration is an amphibolic process since its intermediates such as α-ketoglutarate and oxaloacetate act as precursors for biosynthetic pathways. Hence, both (A) and (R) are correct and (R) properly explains (A). The correct answer is option 1, showing integration of energy and biosynthesis in metabolism.
8. Matching Type
Match the organelle with its function:
A. Mitochondria – (i) ATP synthesis
B. Chloroplast – (ii) Photosynthesis
C. Nucleus – (iii) Genetic control
D. Ribosome – (iv) Protein synthesis
Options:
1. A-(i), B-(ii), C-(iii), D-(iv)
2. A-(ii), B-(i), C-(iv), D-(iii)
3. A-(iii), B-(ii), C-(i), D-(iv)
4. A-(iv), B-(iii), C-(ii), D-(i)
Explanation: Mitochondria produce ATP, chloroplasts carry out photosynthesis, nucleus stores genetic material, and ribosomes synthesize proteins. Hence, option 1 is correct, as each organelle performs a unique but interrelated role in maintaining cellular energy, metabolism, and regulation essential for life processes.
9. Fill in the Blanks Type
Porins are present in the _______ membrane of mitochondria.
1. Inner
2. Outer
3. Cristae
4. Matrix
Explanation: Porins are located in the outer membrane of mitochondria, forming large aqueous channels that allow diffusion of ions and metabolites. They facilitate communication between the cytosol and mitochondrial intermembrane space. Hence, option 2 is correct, as outer membrane porins are essential for metabolic exchange and transport regulation.
10. Choose the Correct Statements Type
Statement I: H+ accumulation occurs in the lumen of thylakoids during light reaction.
Statement II: Respiration is exclusively a catabolic pathway.
1. Both statements are correct.
2. Both statements are incorrect.
3. Statement I is correct, Statement II is incorrect.
4. Statement I is incorrect, Statement II is correct.
Explanation: H+ accumulation indeed occurs inside the thylakoid lumen during light reactions of photosynthesis, while respiration is an amphibolic pathway, not purely catabolic. Hence, Statement I is correct and Statement II is incorrect. The correct answer is option 3, explaining both processes’ functional interdependence in cellular metabolism.
Topic: Translocation of Food; Subtopic: Girdling Experiment and Role of Phloem
Keyword Definitions:
Girdling Experiment: A process where a ring of bark is removed from a plant stem to demonstrate that food transport occurs through phloem.
Phloem: Vascular tissue responsible for translocation of organic nutrients, mainly sucrose, from leaves to other plant parts.
Xylem: Tissue that conducts water and minerals upward from roots to shoots.
Translocation: Movement of food from source (leaves) to sink (roots, fruits, or seeds) in plants.
Apoplast and Symplast: Pathways for water movement in plants; apoplast involves cell walls, while symplast involves cytoplasmic connections.
Lead Question - 2022 (Abroad)
Which of the following was proved by girdling experiment?
1. Apoplastic movement of water occurs through intercellular spaces
2. Symplastic movement of water occurs through interconnected protoplast
3. Xylem is responsible for uptake of water
4. Phloem is responsible for translocation of food
Explanation: The girdling experiment proves that phloem is responsible for translocation of food. When a ring of bark (including phloem) is removed, food accumulates above the ring, causing swelling. This shows that sugars synthesized in leaves move downward through phloem, not xylem, confirming its role in food transport.
1. The main function of phloem in plants is:
1. Transport of water
2. Transport of food
3. Mechanical support
4. Storage of minerals
Explanation: Phloem transports organic food materials, mainly sucrose, from photosynthetic regions (leaves) to non-photosynthetic parts. This process is known as translocation. The direction of movement can be upward or downward depending on the source-sink relationship within the plant body.
2. The process of removing a ring of bark from a tree trunk is called:
1. Pruning
2. Girdling
3. Decortication
4. Layering
Explanation: Girdling involves removing a complete ring of bark, including phloem, to interrupt food transport. Water movement through xylem continues, but the portion above the girdle swells due to sugar accumulation, confirming the phloem’s role in food translocation.
3. The term “source” in phloem translocation refers to:
1. Storage organs
2. Roots
3. Photosynthetic leaves
4. Flowers
Explanation: In plants, the “source” refers to the region where food (mainly sucrose) is synthesized, such as green leaves. This food is then transported through phloem to “sink” regions that require nutrients, such as roots, fruits, and developing seeds, maintaining the plant’s growth and metabolism.
4. Which of the following cells are involved in food transport in angiosperms?
1. Tracheids and vessels
2. Sieve tubes and companion cells
3. Xylem fibers
4. Parenchyma cells
Explanation: Sieve tube elements and companion cells of phloem transport food. Sieve tubes are living, elongated cells that allow nutrient flow, while companion cells regulate their metabolic activity, providing ATP and controlling loading and unloading of solutes during translocation.
5. Which among the following processes does not involve phloem?
1. Transport of amino acids
2. Transport of hormones
3. Transport of minerals
4. Transport of sucrose
Explanation: The correct answer is transport of minerals, as minerals move through xylem along with water. Phloem mainly transports organic solutes like sucrose, amino acids, and hormones in a bidirectional manner depending on plant needs and developmental stages.
6. Translocation of food occurs from:
1. Sink to source
2. Source to sink
3. Root to leaf only
4. Stem to flower only
Explanation: The correct answer is from source to sink. Food synthesized in leaves (sources) is transported through phloem to non-photosynthetic tissues (sinks) like roots, fruits, and seeds for storage or energy use, ensuring balanced plant growth and development.
7. Assertion (A): Phloem is responsible for translocation of food.
Reason (R): Xylem conducts organic solutes.
1. (A) is correct but (R) is not correct
2. (A) is not correct but (R) is correct
3. Both (A) and (R) are correct, and (R) explains (A)
4. Both (A) and (R) are correct, but (R) does not explain (A)
Explanation: The correct answer is option 1. Phloem, not xylem, translocates organic solutes such as sucrose and amino acids. Xylem mainly conducts water and minerals upward from roots to shoots, whereas phloem transports food bidirectionally depending on the metabolic requirements.
8. Match the following:
A. Phloem → 1. Transport of food
B. Xylem → 2. Transport of water
C. Girdling → 3. Removal of bark
D. Sieve tubes → 4. Conducting elements
1. A-1, B-2, C-3, D-4
2. A-4, B-3, C-1, D-2
3. A-3, B-1, C-4, D-2
4. A-2, B-4, C-3, D-1
Explanation: The correct match is A-1, B-2, C-3, D-4. Phloem transports food, xylem carries water, girdling involves bark removal to prove phloem’s role, and sieve tubes serve as conducting channels in phloem for organic solute transport in plants.
9. Fill in the blank: The food prepared in leaves is mainly transported in the form of ________.
1. Glucose
2. Fructose
3. Sucrose
4. Maltose
Explanation: The correct answer is sucrose. Although glucose is the primary product of photosynthesis, it is converted into sucrose for transport because sucrose is non-reducing and chemically stable. It easily dissolves in water, facilitating efficient long-distance movement through phloem tissue.
10. Choose the correct statements:
a. Girdling experiment demonstrates phloem’s role in food transport.
b. Phloem translocation is unidirectional.
c. Companion cells help sieve tubes in food conduction.
d. Bark removal stops upward water flow.
1. a and c
2. b and d
3. a, b, and c
4. a and d
Explanation: The correct answer is a and c. The girdling experiment confirms that phloem transports food, and companion cells support sieve tubes metabolically. Translocation is bidirectional, and bark removal does not affect water transport, as xylem remains intact.
Topic: Phloem Transport; Subtopic: Translocation of Organic Solutes
Keyword Definitions:
Phloem: A vascular tissue that transports organic nutrients, especially sugars, from leaves to other parts of the plant.
Phloem Sap: A fluid rich in sugars, amino acids, and hormones that flows through sieve tubes during translocation.
Sucrose: A disaccharide sugar formed from glucose and fructose, the main form in which sugar is transported in plants.
Translocation: The movement of organic solutes from sources (leaves) to sinks (roots, fruits, etc.) through the phloem.
Lead Question - 2022 (Abroad)
Phloem sap in the plants mainly consists of:
1. Fructose and water
2. Fructose and sucrose
3. Glucose and water
4. Sucrose and water
Explanation (Answer: 4): Phloem sap primarily contains sucrose and water. Sucrose is the main sugar transported from photosynthetic tissues to storage and growing parts through sieve tubes. The flow is driven by osmotic pressure differences between source and sink regions, enabling efficient distribution of energy-rich compounds.
1. The direction of phloem transport is:
1. Always upward
2. Always downward
3. Multidirectional
4. Unidirectional
Explanation (Answer: 3): Phloem transport is multidirectional because organic solutes can move from source to sink in any direction as required by the plant. Unlike xylem, which shows unidirectional upward flow, phloem translocation depends on metabolic needs and sugar demand at various parts.
2. The pressure-flow hypothesis explains:
1. Transpiration
2. Ascent of sap
3. Translocation of sugars in phloem
4. Guttation
Explanation (Answer: 3): The pressure-flow hypothesis describes how sucrose solution moves from source to sink in phloem. High osmotic pressure at the source drives the movement toward low pressure at the sink. This model best explains the mechanism of phloem sap translocation in plants.
3. In phloem transport, the source is generally the:
1. Root
2. Leaf
3. Flower
4. Fruit
Explanation (Answer: 2): Leaves act as the main source in phloem transport because they produce sugars during photosynthesis. These sugars are then loaded into sieve tubes for transport to other parts of the plant, which function as sinks, such as roots or fruits requiring energy for growth.
4. Phloem loading involves:
1. Active transport of sucrose into sieve tubes
2. Diffusion of sucrose into xylem
3. Osmotic uptake of water by xylem
4. Active transport of ions into guard cells
Explanation (Answer: 1): Phloem loading is an active process that transfers sucrose from mesophyll cells into sieve tube elements using ATP. This increases osmotic pressure, drawing water from xylem and initiating bulk flow of phloem sap toward the sink tissues where sugars are consumed or stored.
5. Which one of the following helps in phloem transport?
1. Tracheids
2. Vessel elements
3. Companion cells
4. Guard cells
Explanation (Answer: 3): Companion cells assist sieve tube elements in phloem transport by providing metabolic support and helping with active loading and unloading of sucrose. They maintain the concentration gradient necessary for translocation and ensure continuous flow of nutrients throughout the plant body.
6. Which one is the conducting element of phloem?
1. Xylem vessels
2. Sieve tube elements
3. Tracheids
4. Fibers
Explanation (Answer: 2): Sieve tube elements are the main conducting units of phloem. They are elongated living cells connected end-to-end with sieve plates for sap movement. Though they lack a nucleus, companion cells regulate their functions, enabling efficient transport of sucrose and other solutes through the plant.
7. (Assertion-Reason Type)
Assertion: Phloem transport is an active process.
Reason: Loading and unloading of sugars into the phloem require energy.
1. Both Assertion and Reason are true, and Reason is the correct explanation
2. Both Assertion and Reason are true, but Reason is not the correct explanation
3. Assertion is true, but Reason is false
4. Both Assertion and Reason are false
Explanation (Answer: 1): Phloem transport requires metabolic energy for sugar loading and unloading into sieve tubes, making it an active process. ATP-driven transport establishes osmotic gradients that cause pressure flow, moving sucrose-rich sap from sources like leaves to sinks such as roots or fruits efficiently.
8. (Matching Type)
Match the parts of phloem with their functions:
a. Sieve tube elements
b. Companion cells
c. Phloem fibers
d. Phloem parenchyma
(i) Storage of food
(ii) Mechanical support
(iii) Translocation of food
(iv) Support and loading of sucrose
1. (a)-(iii), (b)-(iv), (c)-(ii), (d)-(i)
2. (a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)
3. (a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)
4. (a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)
Explanation (Answer: 1): Sieve tubes transport food, companion cells support and load sucrose, phloem fibers provide mechanical strength, and phloem parenchyma stores food. These components work collectively to maintain the translocation process and structural integrity of phloem tissue for efficient nutrient distribution.
9. (Fill in the Blanks)
Phloem translocation occurs from ________ to ________.
Explanation (Answer: source, sink): Phloem translocation occurs from source to sink regions. Sources are photosynthetic parts that produce sugars, while sinks are areas like roots, fruits, or young leaves where sugars are consumed or stored. This flow is controlled by osmotic gradients in the sieve tubes.
10. (Choose the correct statements)
a. Phloem sap moves by pressure flow
b. Movement of phloem sap is bidirectional
c. Phloem translocation requires metabolic energy
d. Phloem sap mainly contains glucose
1. a, b, and c only
2. b and d only
3. a and c only
4. a, b, c, and d
Explanation (Answer: 1): Phloem sap moves by pressure flow from high osmotic pressure regions to low pressure regions. The process is bidirectional depending on the source-sink relationship and needs energy for sugar loading. The sap primarily contains sucrose, not glucose, as the major transport sugar.
Topic: Transport Across Cell Membrane
Subtopic: Facilitated Diffusion
Keyword Definitions:
Facilitated Diffusion: Passive transport of molecules across a biological membrane via specific transport proteins without energy expenditure.
Porins: Protein channels that allow the passage of certain molecules across membranes, mainly in mitochondria and bacteria.
Concentration Gradient: The gradual difference in solute concentration between two areas, driving diffusion.
ATP: Adenosine Triphosphate, the main energy currency of the cell.
Lead Question - 2022 (Abroad)
Which of the following statements about facilitated diffusion is incorrect?
1. Special proteins of the membrane help in this process
2. Porins are involved in this process
3. Movement of molecule occurs against the concentration gradient
4. ATP is not required for this process
Explanation (Answer: 3): Facilitated diffusion is a passive process that moves molecules along the concentration gradient through specific transport proteins. It does not require ATP. Movement against the gradient occurs only in active transport, not in facilitated diffusion. Hence, statement 3 is incorrect because it describes active transport.
1. The main difference between simple diffusion and facilitated diffusion is:
1. Use of carrier proteins
2. Requirement of ATP
3. Movement of gases only
4. Movement of ions only
Explanation (Answer: 1): Facilitated diffusion uses specific carrier or channel proteins to help molecules move across membranes, unlike simple diffusion which occurs freely. Both are passive processes and do not require energy. Thus, the primary difference lies in the involvement of membrane transport proteins.
2. Which of the following molecules moves by facilitated diffusion?
1. Oxygen
2. Carbon dioxide
3. Glucose
4. Water
Explanation (Answer: 3): Glucose moves across cell membranes by facilitated diffusion with the help of GLUT transporters. Since it is a large polar molecule, it cannot pass through the lipid bilayer by simple diffusion. Therefore, carrier proteins assist in its passive transport down the concentration gradient.
3. Facilitated diffusion differs from active transport because it:
1. Requires ATP
2. Is slower
3. Occurs against the gradient
4. Does not require energy
Explanation (Answer: 4): Facilitated diffusion is a passive process where solutes move along their concentration gradient through specific transport proteins without using cellular energy. In contrast, active transport needs ATP to move molecules against the concentration gradient, making facilitated diffusion an energy-efficient process.
4. Porins form channels in the outer membranes of:
1. Lysosomes
2. Mitochondria
3. Endoplasmic reticulum
4. Nucleus
Explanation (Answer: 2): Porins are large transmembrane proteins that form channels in the outer membranes of mitochondria, chloroplasts, and some bacteria. They allow small hydrophilic molecules to pass through, enabling efficient exchange of ions and metabolites essential for cellular metabolism and respiration.
5. The rate of facilitated diffusion depends on:
1. ATP concentration
2. Number of carrier proteins
3. Cell wall thickness
4. Availability of enzymes
Explanation (Answer: 2): Facilitated diffusion depends on the number of carrier or channel proteins present in the membrane. When all carrier proteins are occupied, the rate reaches saturation. Therefore, increasing protein availability enhances the transport rate until all become occupied by substrate molecules.
6. In facilitated diffusion, carrier proteins exhibit:
1. Enzymatic action
2. Specificity and saturation
3. Random movement
4. Constant activity
Explanation (Answer: 2): Carrier proteins show specificity for certain molecules and saturation when all binding sites are occupied. This characteristic makes facilitated diffusion similar to enzyme kinetics. Specificity ensures that only suitable solutes are transported, maintaining selective permeability of the biological membrane.
7. (Assertion-Reason Type)
Assertion: Facilitated diffusion is a passive process.
Reason: It uses ATP to move molecules across the membrane.
1. Both Assertion and Reason are true and Reason is the correct explanation
2. Both Assertion and Reason are true but Reason is not the correct explanation
3. Assertion is true but Reason is false
4. Assertion is false but Reason is true
Explanation (Answer: 3): The assertion is true because facilitated diffusion occurs passively without energy expenditure. The reason is false because ATP is not used in this process. The movement occurs along the concentration gradient using membrane proteins, distinguishing it from active transport.
8. (Matching Type)
Match the transport type with its characteristics:
a. Simple diffusion
b. Facilitated diffusion
c. Active transport
d. Osmosis
(i) Energy independent and uses carriers
(ii) Energy dependent
(iii) Movement of water molecules
(iv) Direct movement through lipid bilayer
1. (a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)
2. (a)-(i), (b)-(ii), (c)-(iv), (d)-(iii)
3. (a)-(iii), (b)-(ii), (c)-(i), (d)-(iv)
4. (a)-(iv), (b)-(ii), (c)-(iii), (d)-(i)
Explanation (Answer: 1): Simple diffusion passes directly through membranes, facilitated diffusion uses carriers but no energy, active transport needs energy, and osmosis involves water movement. This classification helps differentiate passive and active transport mechanisms based on energy dependence and direction of molecule movement.
9. (Fill in the Blanks)
Facilitated diffusion allows ________ molecules to cross membranes through specific transport proteins.
Explanation (Answer: polar): Facilitated diffusion enables polar molecules like glucose and amino acids to pass across membranes using channel or carrier proteins. Since lipid bilayers restrict polar solute movement, transport proteins provide hydrophilic pathways ensuring selective permeability and efficient cellular transport processes without energy use.
10. (Choose the correct statements)
a. Facilitated diffusion requires ATP
b. It shows saturation
c. Carrier proteins are specific
d. It moves molecules along concentration gradient
1. a and b
2. b, c, and d
3. a, b, and d
4. c and d
Explanation (Answer: 2): Facilitated diffusion shows saturation and specificity due to carrier proteins and moves molecules along their concentration gradient. It is an energy-independent process that depends on the availability and selectivity of transport proteins, maintaining controlled molecular exchange across cell membranes.
Subtopic: Water Potential and Osmosis
Keyword Definitions:
Water Potential: The potential energy of water in a system compared to pure water, determining the direction of water movement.
Solute Potential: The component of water potential affected by dissolved solutes; it always lowers total water potential.
Osmosis: Movement of water across a semi-permeable membrane from higher to lower water potential.
Diffusion: Passive movement of molecules from a region of high concentration to low concentration.
Plasmolysis: The shrinkage of the cytoplasm from the cell wall due to water loss in a hypertonic solution.
Turgor Pressure: The pressure exerted by the cell contents against the cell wall, maintaining cell rigidity.
Semipermeable Membrane: A membrane allowing certain molecules (usually water) to pass but restricting solutes.
Hypotonic Solution: A solution having higher water potential than the cell sap, causing water entry into the cell.
Hypertonic Solution: A solution having lower water potential than the cell sap, causing water to leave the cell.
Osmotic Potential: Another term for solute potential, representing the effect of solute concentration on water potential.
Lead Question (2022)
Addition of solutes in a given solution will:
(1) Lower its water potential
(2) Make its water
(3) Not affect the water potential at all
(4) Raise its water potential
Explanation:
When solutes are added to pure water, solute potential becomes more negative, reducing total water potential. Thus, addition of solutes lowers water potential, making water move toward it from higher potential regions. Correct answer is (1).
1. Single Correct Answer MCQ:
What is the water potential of pure water at standard conditions?
(1) Zero
(2) One
(3) Negative
(4) Positive
Explanation:
Pure water has a water potential of zero at standard conditions (25°C and 1 atm). Solutes or pressure can make it more negative or positive, respectively. Correct answer is (1).
2. Single Correct Answer MCQ:
Which of the following will increase the water potential of a cell?
(1) Decrease in solute concentration
(2) Increase in solute concentration
(3) Water loss
(4) Plasmolysis
Explanation:
Decreasing solute concentration reduces solute potential negativity, thus increasing total water potential. Correct answer is (1).
3. Single Correct Answer MCQ:
In a hypertonic solution, a plant cell will:
(1) Gain water
(2) Lose water
(3) Remain unchanged
(4) Become more turgid
Explanation:
In a hypertonic solution, external water potential is lower than inside the cell, so water exits the cell, causing plasmolysis. Correct answer is (2).
4. Single Correct Answer MCQ:
The component of water potential affected by solutes is called:
(1) Pressure potential
(2) Solute potential
(3) Osmotic pressure
(4) Diffusion pressure
Explanation:
Solute potential (Ψs) represents the effect of solutes on water potential; it is always negative. Correct answer is (2).
5. Single Correct Answer MCQ:
Water moves from a region of:
(1) Low water potential to high water potential
(2) High solute potential to low solute potential
(3) High water potential to low water potential
(4) Negative pressure to positive pressure
Explanation:
Water always moves from a region of higher water potential to one with lower water potential until equilibrium is reached. Correct answer is (3).
6. Single Correct Answer MCQ:
The water potential of a fully turgid cell is:
(1) Zero
(2) Negative
(3) Positive
(4) Equal to solute potential
Explanation:
A fully turgid cell has pressure potential equal in magnitude but opposite to solute potential, making total water potential zero. Correct answer is (1).
7. Assertion-Reason MCQ:
Assertion (A): Addition of solutes decreases water potential.
Reason (R): Solute potential is always positive.
Options:
(1) Both A and R are true, R explains A
(2) Both A and R are true, R does not explain A
(3) A is true, R is false
(4) A is false, R is true
Explanation:
Addition of solutes lowers water potential because solute potential is negative, not positive. Thus, the assertion is correct but reason is false. Correct answer is (3).
8. Matching Type MCQ:
Match the terms with their correct descriptions:
A. Solute potential — 1. Positive in turgid cells
B. Pressure potential — 2. Negative component
C. Water potential — 3. Sum of all potentials
D. Osmosis — 4. Movement of water across membrane
Options:
(1) A–2, B–1, C–3, D–4
(2) A–1, B–2, C–3, D–4
(3) A–2, B–3, C–4, D–1
(4) A–4, B–2, C–1, D–3
Explanation:
Solute potential is negative (2), pressure potential is positive (1), water potential is total of all potentials (3), and osmosis is water movement across membranes (4). Correct matching is (1).
9. Fill in the Blanks MCQ:
The water potential of a solution always becomes ________ when solutes are added.
(1) Higher
(2) Lower
(3) Equal
(4) Unchanged
Explanation:
Adding solutes lowers water potential because solute potential becomes more negative. Correct answer is (2).
10. Choose the Correct Statements MCQ:
(a) Water potential is zero for pure water
(b) Solute potential is always negative
(c) Pressure potential in a turgid cell is positive
(d) Addition of solutes increases water potential
Options:
(1) a, b, c
(2) a, b, d
(3) b, c, d
(4) a, c, d
Explanation:
Pure water has zero potential (a), solute potential is negative (b), and turgid cell pressure potential is positive (c). Addition of solutes decreases water potential, so (d) is wrong. Correct answer is (1).
Subtopic: Phloem Transport and Experiments
Keyword Definitions:
Girdling Experiment: A method where a ring of bark is removed from a stem to study transport of food.
Phloem: Vascular tissue responsible for transporting organic food from leaves to other plant parts.
Xylem: Vascular tissue that transports water and minerals from roots to shoots.
Osmosis: Movement of water across a semi-permeable membrane from high to low water potential.
Transport in Plants: Movement of water, minerals, and food through xylem and phloem.
Lead Question (2022)
“Girdling Experiment” was performed by Plant Physiologists to identify the plant tissue through which:
Options:
(1) Food is transported
(2) For both water and food transportation
(3) Osmosis is observed
(4) Water is transported
Explanation:
The girdling experiment involves removing a ring of bark, which contains phloem, from the stem. Accumulation of food above the girdle confirms that phloem is responsible for transporting organic food. Water transport occurs through xylem and is unaffected. Correct answer is (1). This experiment demonstrates the role of phloem in translocation.
1. Which plant tissue transports water from roots to leaves?
(1) Phloem
(2) Xylem
(3) Cambium
(4) Cortex
Explanation:
Xylem is specialized for transporting water and dissolved minerals from roots to aerial parts of the plant, using transpiration pull. Phloem transports food, not water. Correct answer is (2).
2. In the girdling experiment, what accumulates above the girdle?
(1) Water
(2) Organic food
(3) Minerals
(4) Oxygen
Explanation:
When the bark containing phloem is removed, organic food synthesized in leaves accumulates above the girdle because phloem transport is blocked. Water and minerals move through xylem and are not affected. Correct answer is (2).
3. Which tissue is mainly removed in a girdling experiment?
(1) Xylem
(2) Phloem
(3) Cambium
(4) Pith
Explanation:
The bark removed during girdling contains phloem, responsible for food transport. Xylem remains intact for water transport. This allows identification of phloem function. Correct answer is (2).
4. What is the role of xylem in plants?
(1) Translocation of sugars
(2) Transport of water and minerals
(3) Photosynthesis
(4) Storing food
Explanation:
Xylem conducts water and dissolved minerals from roots to aerial parts through transpiration pull and cohesion. It does not transport sugars or perform photosynthesis. Correct answer is (2).
5. Single Correct Answer MCQ:
The accumulation of organic food above a girdle confirms:
(1) Phloem transports food
(2) Xylem transports water
(3) Cambium produces secondary growth
(4) Cortex stores starch
Explanation:
Food accumulates above the removed bark containing phloem, confirming that phloem is responsible for translocation of organic nutrients. Xylem continues to transport water unaffected. Correct answer is (1).
6. Which of the following is affected in a girdling experiment?
(1) Phloem transport
(2) Xylem transport
(3) Both phloem and xylem
(4) Only root growth
Explanation:
Girdling removes the bark containing phloem, blocking food transport. Xylem remains intact, allowing water movement. Root growth may reduce over time due to lack of food but initially is unaffected. Correct answer is (1).
7. Assertion-Reason MCQ:
Assertion (A): Girdling blocks translocation of food.
Reason (R): Phloem is removed in the girdled portion.
Options:
(1) Both A and R are correct, R explains A
(2) A correct, R incorrect
(3) A incorrect, R correct
(4) Both A and R incorrect
Explanation:
Removal of phloem in girdling interrupts food translocation, leading to accumulation above the girdle. The assertion is true and reason correctly explains it. Correct answer is (1).
8. Matching Type MCQ:
Match plant tissue with function:
A. Xylem — 1. Transport water
B. Phloem — 2. Transport food
Options:
(1) A–1, B–2
(2) A–2, B–1
(3) Both A and B – 1
(4) Both A and B – 2
Explanation:
Xylem transports water and minerals (1), while phloem transports organic food (2). Correct answer is (1).
9. Fill in the Blanks:
The vascular tissue responsible for food translocation is _______.
(1) Phloem
(2) Xylem
(3) Cambium
(4) Cortex
Explanation:
Phloem conducts organic nutrients from leaves to various parts. Xylem only conducts water. Correct answer is (1).
10. Choose the Correct Statements:
(a) Girdling removes phloem
(b) Food accumulates above girdle
(c) Xylem transport is blocked
(d) Water transport continues
Options:
(1) a, b, d
(2) a and c only
(3) b and c only
(4) all of the above
Explanation:
Girdling removes phloem (a), causing food accumulation above the girdle (b). Xylem is unaffected, so water transport continues (d). Correct answer is (1).
Topic: Movement of Water in Plants
Subtopic: Apoplastic and Symplastic Pathways
Keyword Definitions:
Apoplast: It includes cell walls and intercellular spaces through which water moves without crossing the cell membrane.
Symplast: It refers to the movement of substances through the interconnected cytoplasm of cells via plasmodesmata.
Plasmodesmata: Cytoplasmic connections between adjacent plant cells that allow exchange of materials.
Water potential: The potential energy of water that determines the direction of water movement in plants.
Lead Question – 2022
Which of the following is not observed during apoplastic pathway?
(1) The movement does not involve crossing of cell membrane
(2) The movement is aided by cytoplasmic streaming
(3) Apoplast is continuous and does not provide any barrier to water movement
(4) Movement of water occurs through intercellular spaces and wall of the cells
Explanation: The apoplastic pathway involves water movement through cell walls and intercellular spaces without crossing the plasma membrane. It is not aided by cytoplasmic streaming, which occurs in the symplastic pathway. Hence, option (2) is correct. Apoplastic movement stops at the Casparian strip in the endodermis. (50 words)
Guessed Questions:
1. The symplastic movement of water in plants occurs through:
(1) Cell walls
(2) Vacuoles
(3) Cytoplasm and plasmodesmata
(4) Xylem vessels
Explanation: Symplastic movement occurs through cytoplasm interconnected by plasmodesmata. This allows direct transfer of ions and water molecules between adjacent cells. It requires crossing the plasma membrane only once and is aided by cytoplasmic streaming. Therefore, the correct answer is (3) cytoplasm and plasmodesmata. (50 words)
2. Which structure in the root prevents apoplastic movement of water to the stele?
(1) Endodermis
(2) Cortex
(3) Epidermis
(4) Pericycle
Explanation: The Casparian strip present in the endodermis contains suberin, a waxy material that blocks the apoplastic pathway. This ensures water and solutes must enter the symplast to reach the xylem. Hence, endodermis acts as a selective barrier. Correct answer: (1) Endodermis. (50 words)
3. In the apoplastic pathway, the movement of water is driven mainly by:
(1) Active transport
(2) Osmotic potential
(3) Transpiration pull
(4) Pressure potential
Explanation: Apoplastic water movement depends on transpiration pull, creating a continuous water column through cell walls. This passive process is pressure-driven, not energy-dependent. Hence, option (3) transpiration pull is correct. It operates efficiently until reaching the endodermal Casparian strip, where apoplastic movement ceases. (50 words)
4. Assertion (A): Apoplastic pathway provides a faster route for water movement.
Reason (R): Water in apoplast does not cross plasma membranes.
(1) Both A and R are true, and R is the correct explanation of A.
(2) Both A and R are true, but R is not the correct explanation of A.
(3) A is true, but R is false.
(4) A is false, but R is true.
Explanation: Both assertion and reason are true. The apoplastic route is faster because water moves through non-living cell walls and intercellular spaces, avoiding plasma membrane crossing. Hence, R correctly explains A. Therefore, the correct option is (1). (50 words)
5. Match the following pathways with their characteristics:
A. Apoplastic pathway – (i) Cytoplasmic streaming
B. Symplastic pathway – (ii) Cell walls
C. Transmembrane route – (iii) Crossing membrane repeatedly
Choose the correct match:
(1) A–ii, B–i, C–iii
(2) A–iii, B–ii, C–i
(3) A–i, B–ii, C–iii
(4) A–ii, B–iii, C–i
Explanation: The apoplastic route occurs via cell walls, symplastic through cytoplasmic streaming, and transmembrane involves repeated membrane crossing. Hence, the correct matching is A–ii, B–i, C–iii, corresponding to option (1). (50 words)
6. In which plant organ is apoplastic movement of water most prominent?
(1) Root hairs
(2) Endodermis
(3) Xylem vessels
(4) Phloem
Explanation: Apoplastic movement predominates in root hairs, cortex, and xylem vessels, as these structures provide continuous cell wall channels for water movement without crossing membranes. Hence, the correct answer is (3) xylem vessels. (50 words)
7. Fill in the blank:
The endodermal cells contain a waxy layer called ______ that blocks apoplastic flow.
(1) Cutin
(2) Suberin
(3) Lignin
(4) Cellulose
Explanation: The Casparian strip in endodermal cell walls is rich in suberin, a hydrophobic substance that prevents apoplastic movement into the vascular cylinder. This forces water into the symplastic route. Hence, the correct answer is (2) suberin. (50 words)
8. Choose the correct statements regarding apoplastic pathway:
(1) It occurs through cytoplasm
(2) It is faster than symplastic movement
(3) It requires energy
(4) It stops at Casparian strip
Explanation: Apoplastic movement is faster as it occurs through cell walls but halts at the Casparian strip. It does not require energy or cytoplasmic streaming. Correct statements: (2) and (4). (50 words)
9. In apoplastic pathway, which component of cell wall plays a key role in water movement?
(1) Cellulose microfibrils
(2) Cuticle
(3) Suberin
(4) Pectin
Explanation: Cellulose microfibrils form a hydrophilic network that allows capillary movement of water through cell walls in apoplastic transport. Hence, the correct answer is (1) cellulose microfibrils. (50 words)
10. Apoplastic movement ceases at which location in the root?
(1) Cortex
(2) Epidermis
(3) Endodermis
(4) Pericycle
Explanation: The Casparian strip present in the endodermal cell wall prevents further apoplastic water movement into the vascular tissues. Water must enter the symplast beyond this point. Hence, the correct answer is (3) endodermis. (50 words)
Topic: Water Relations in Plants
Subtopic: Cohesion, Adhesion, Surface Tension, and Guttation
Keyword Definitions:
Cohesion: The mutual attraction between water molecules due to hydrogen bonding.
Adhesion: The attraction of water molecules toward other polar surfaces like cell walls.
Surface Tension: The property of water surface to resist external force, caused by stronger cohesion among molecules.
Guttation: The loss of water in liquid form from leaf tips or margins due to root pressure.
Hydrogen Bond: A weak bond formed between the hydrogen atom of one molecule and an electronegative atom of another molecule.
Root Pressure: Upward push of water in xylem due to osmotic pressure in roots.
Polar Surface: A surface that has a partial positive and negative charge attracting water molecules.
Liquid Phase Water Loss: Water loss in liquid form instead of transpiration as vapor.
Lead Question - 2021
Match List - I with List - II.
List - I List - II
(a) Cohesion (i) More attraction in liquid phase
(b) Adhesion (ii) Mutual attraction among water molecules
(c) Surface tension (iii) Water loss in liquid phase
(d) Guttation (iv) Attraction towards polar surfaces
Choose the correct answer:
(a) (b) (c) (d)
(1) (iv) (iii) (ii) (i)
(2) (iii) (i) (iv) (ii)
(3) (ii) (i) (iv) (iii)
(4) (ii) (iv) (i) (iii)
Explanation: The correct answer is (4) (ii) (iv) (i) (iii). Cohesion refers to mutual attraction among water molecules (ii), adhesion is water attraction towards polar surfaces (iv), surface tension results from more attraction in liquid phase (i), and guttation is water loss in liquid form from leaf tips (iii). This sequence reflects water relations accurately.
Guessed Questions:
1) Which property of water causes it to rise in narrow capillaries?
(1) Cohesion
(2) Adhesion
(3) Surface tension
(4) Guttation
Explanation: The correct answer is (2) Adhesion. Water molecules are attracted to polar surfaces of xylem vessels, assisting capillary rise. Adhesion, along with cohesion, facilitates the upward movement of water from roots to leaves, a key mechanism in plant water transport.
2) Assertion (A): Cohesion is responsible for surface tension.
Reason (R): Hydrogen bonds between water molecules create mutual attraction.
(1) Both A and R true, R explains A
(2) Both A and R true, R does not explain A
(3) A true, R false
(4) A false, R true
Explanation: The correct answer is (1). Surface tension arises because water molecules cohere due to hydrogen bonding. Cohesion creates a resistant surface layer, allowing water to form droplets and support small objects, which is essential in maintaining water column integrity in plants.
3) Which of the following is directly caused by root pressure?
(1) Transpiration
(2) Guttation
(3) Cohesion
(4) Adhesion
Explanation: The correct answer is (2) Guttation. Root pressure builds up in the xylem, pushing water to leaf margins where it is exuded as liquid droplets. This phenomenon occurs in conditions of high soil moisture and low transpiration.
4) Fill in the blank: The mutual attraction among water molecules due to hydrogen bonding is called ________.
(1) Adhesion
(2) Cohesion
(3) Surface tension
(4) Capillarity
Explanation: The correct answer is (2) Cohesion. Hydrogen bonds between water molecules create a strong internal attraction, allowing water to stick to itself. Cohesion is vital for water transport in xylem and contributes to surface tension, which stabilizes the water column in plants.
5) Which property allows water to adhere to cell walls and xylem vessels?
(1) Surface tension
(2) Cohesion
(3) Adhesion
(4) Guttation
Explanation: The correct answer is (3) Adhesion. Adhesion is the attraction of water molecules to polar surfaces, such as xylem walls. This property, combined with cohesion, assists in the capillary movement of water from roots to leaves in plants.
6) Which factor primarily contributes to high surface tension in water?
(1) Cohesion
(2) Adhesion
(3) Gravity
(4) Root pressure
Explanation: The correct answer is (1) Cohesion. The mutual attraction among water molecules due to hydrogen bonding forms a tensioned surface layer at the air-water interface. This property enables water to resist external force and aids in processes like water transport in plants.
7) Choose the correct statements:
a. Cohesion is mutual attraction among water molecules.
b. Adhesion helps in capillary rise.
c. Guttation occurs during high transpiration.
d. Surface tension is due to cohesion.
(1) a, b, d
(2) a, c
(3) b, c, d
(4) a, b, c, d
Explanation: The correct answer is (1) a, b, d. Cohesion causes water molecules to stick together, adhesion facilitates capillary rise, and surface tension arises from cohesion. Guttation occurs when transpiration is low and root pressure is high, making statement c incorrect.
8) Assertion (A): Guttation is water loss in liquid form from leaves.
Reason (R): It occurs due to root pressure in xylem when transpiration is low.
(1) Both A and R true, R explains A
(2) Both A and R true, R does not explain A
(3) A true, R false
(4) A false, R true
Explanation: The correct answer is (1). Guttation results from the exudation of liquid water through hydathodes at leaf margins. It is caused by root pressure when transpiration is minimal, typically at night or high humidity, allowing water to escape in liquid form.
9) Matching Type: Match the plant water relation term with its description.
List-I List-II
(a) Cohesion (i) Water loss in liquid
(b) Adhesion  
Subtopic: Phloem and Xylem Transport
Keyword Definitions:
Phloem: Vascular tissue responsible for translocation of organic solutes, mainly sucrose.
Xylem: Vascular tissue that transports water and minerals from roots to aerial parts.
Bidirectional transport: Movement in two directions, e.g., in phloem from source to sink.
Unidirectional transport: Movement in a single direction, e.g., water in xylem.
Source: Part of plant producing or storing assimilates, e.g., leaves.
Sink: Part of plant consuming or storing assimilates, e.g., roots, fruits.
ATP: Adenosine triphosphate, energy currency required for active transport.
Minerals: Inorganic nutrients like nitrogen, phosphorus, potassium, sulfur.
Loading: Process of moving sucrose into phloem at source.
Unloading: Process of removing sucrose from phloem at sink.
Mobilization: Movement of nutrients from one region to another within plant.
Lead Question - 2020 (COVID Reexam)
Select the incorrect statement.
1. Transport of molecules in phloem can be bidirectional.
2. The movement of minerals in the xylem is unidirectional.
3. Unloading of sucrose at the sink does not involve the utilization of ATP.
4. Elements most easily mobilized in plants from one region to another are phosphorus, sulfur, nitrogen, and potassium.
Explanation: Phloem transport is bidirectional, xylem transport is unidirectional, and macronutrients like phosphorus, sulfur, nitrogen, and potassium are highly mobile. Unloading of sucrose at the sink requires energy in the form of ATP for active transport. Hence, option 3 is incorrect. Proper ATP utilization ensures efficient phloem unloading. (50 words)
Guessed Question 1. Single Correct Answer MCQ: Which vascular tissue transports water and minerals?
1. Phloem
2. Xylem
3. Collenchyma
4. Sclerenchyma
Explanation: Xylem is responsible for unidirectional transport of water and minerals from roots to leaves. Phloem translocates organic solutes. Collenchyma and sclerenchyma provide support. Correct answer is option 2: Xylem. Efficient water transport is vital for plant turgor, nutrient distribution, and photosynthesis. (50 words)
Guessed Question 2. Single Correct Answer MCQ: Phloem transport is generally :
1. Unidirectional
2. Bidirectional
3. Non-directional
4. Random
Explanation: Phloem transport can occur in both directions, from source to sink, depending on the plant's needs. Unidirectional transport is typical of xylem. Correct answer is option 2: Bidirectional. This flexibility allows distribution of nutrients to growing or storage organs. (50 words)
Guessed Question 3. Single Correct Answer MCQ: Which nutrient is highly mobile in plants?
1. Calcium
2. Phosphorus
3. Iron
4. Boron
Explanation: Phosphorus is highly mobile within plants, easily moving from older to younger tissues. Calcium and boron are relatively immobile, and iron mobility is limited. Correct answer is option 2: Phosphorus. Mobility ensures nutrient availability for growth and metabolic activities. (50 words)
Guessed Question 4. Single Correct Answer MCQ: Active sucrose unloading at sink requires :
1. ATP
2. Water
3. Oxygen only
4. Minerals
Explanation: Active transport of sucrose into sink cells requires ATP energy to move molecules against concentration gradients. Passive transport occurs in some cases, but efficient unloading depends on ATP. Correct answer is option 1: ATP. Energy ensures sucrose is available for growth, storage, and metabolism. (50 words)
Guessed Question 5. Assertion-Reason MCQ:
Assertion (A): Xylem transport is unidirectional.
Reason (R): Water and minerals move only from roots to shoots.
1. Both A and R true, R explains A
2. Both A and R true, R not correct explanation
3. A true, R false
4. A false, R true
Explanation: Xylem transport is unidirectional, moving water and minerals from roots to aerial parts. Both assertion and reason are true, and R explains A. Correct answer is option 1. This directional flow is essential for maintaining plant hydration, nutrient supply, and turgor pressure. (50 words)
Guessed Question 6. Matching Type MCQ:
Column I - Function
(a) Phloem transport (i) Water and minerals
(b) Xylem transport (ii) Sucrose and nutrients
(c) Sucrose loading (iii) Energy dependent
(d) Sucrose unloading (iv) Bidirectional transport
Options:
1. (a)-(ii), (b)-(i), (c)-(iii), (d)-(iv)
2. (a)-(iv), (b)-(i), (c)-(iii), (d)-(ii)
3. (a)-(ii), (b)-(iv), (c)-(i), (d)-(iii)
4. (a)-(i), (b)-(ii), (c)-(iv), (d)-(iii)
Explanation: Phloem translocates sucrose bidirectionally, xylem moves water and minerals unidirectionally. Sucrose loading and unloading are energy dependent. Correct answer is option 1. Proper functioning ensures efficient nutrient distribution and plant growth. (50 words)
Guessed Question 7. Fill in the blank:
Transport of water and minerals through xylem is _______.
1. Bidirectional
2. Unidirectional
3. Random
4. Nonexistent
Explanation: Xylem transport is unidirectional, moving water and minerals from roots to aerial parts. This ensures continuous hydration, nutrient supply, and transpiration pull. Correct answer is option 2: Unidirectional. Proper directionality is critical for plant survival and metabolic activities. (50 words)
Guessed Question 8. Single Correct Answer MCQ: Elements most easily mobilized in plants include :
1. Calcium and boron
2. Nitrogen, phosphorus, potassium, sulfur
3. Iron and manganese
4. Zinc and copper
Explanation: Nitrogen, phosphorus, potassium, and sulfur are highly mobile, allowing redistribution from older to younger tissues. Calcium, boron, and micronutrients are less mobile. Correct answer is option 2. Mobility ensures nutrient availability for growth, reproduction, and metabolic activities. (50 words)
Guessed Question 9. Single Correct Answer MCQ: Which process requires energy at sink?
1. Sucrose unloading
2. Xylem transport
3. Transpiration pull
4. Passive diffusion
Explanation: Sucrose unloading at the sink is an active process requiring ATP, moving sucrose into cells against the concentration gradient. Xylem transport is passive, driven by transpiration. Correct answer is option 1. ATP ensures efficient nutrient distribution for growth and storage. (50 words)
Guessed Question 10. Choose correct statements:
1. Phloem transport is bidirectional
2. Xylem transport is unidirectional
3. Sucrose unloading requires energy
4. Phosphorus, sulfur, nitrogen, potassium are mobile
Options:
A. 1 and 2
B. 1, 2, and 3
C. 1, 2, 3, and 4
D. 2, 3, and 4
Explanation: All statements are correct: phloem is bidirectional, xylem unidirectional, sucrose unloading is energy-dependent, and macronutrients are mobile. Correct answer is option C: 1, 2, 3, and 4. These coordinated transport mechanisms ensure proper distribution of water, nutrients, and organic solutes. (50 words)
Subtopic: Mechanisms of Water Movement
Imbibition: Absorption of water by solids like seeds or wood, causing swelling.
Plasmolysis: Shrinkage of cell protoplast due to water loss in hypertonic solution.
Transpiration: Loss of water vapor from plant surfaces, mainly through stomata.
Root pressure: Positive pressure in roots that can push water upwards in xylem.
Guttation: Exudation of liquid water from leaf tips or edges, usually at night.
Stomata: Pores on leaf surface controlling gas exchange and transpiration.
Xylem: Tissue transporting water and minerals from roots to shoots.
Water potential: Measure of potential energy of water in a system, affecting movement.
Cohesion and adhesion: Properties of water molecules enabling upward movement in xylem.
Leaf blade: Flat part of leaf where transpiration and photosynthesis occur.
Root system: Organ system absorbing water and minerals, contributing to root pressure.
Lead Question (2020): The process responsible for facilitating loss of water in liquid form from the tip of grass blades at night and in early morning is :
Imbibition
Plasmolysis
Transpiration
Root pressure
Explanation: The correct answer is 4. Root pressure in plants generates positive pressure in xylem during night or early morning, forcing water out as droplets at leaf tips, a phenomenon called guttation. Transpiration involves vapor loss, not liquid. Imbibition and plasmolysis do not cause water exudation in this context.
Guessed MCQs:
Question 1: Guttation is caused by:
A. Imbibition
B. Root pressure
C. Transpiration
D. Plasmolysis
Explanation: The correct answer is B. Guttation occurs due to root pressure pushing water through hydathodes at night or early morning. Transpiration involves vapor loss, and imbibition or plasmolysis are unrelated processes.
Question 2: Transpiration primarily involves loss of:
A. Liquid water from leaf tips
B. Water vapor from stomata
C. Water from xylem under pressure
D. Water absorbed by roots
Explanation: The correct answer is B. Transpiration is the loss of water vapor from plant aerial parts, mainly through stomata. It differs from guttation, which is liquid water exudation facilitated by root pressure.
Question 3: Hydathodes are associated with:
A. Absorption of water
B. Liquid exudation at leaf edges
C. Photosynthesis
D. Stomatal opening
Explanation: The correct answer is B. Hydathodes at leaf margins allow guttation. Root pressure forces water through hydathodes at night or early morning. Stomata regulate transpiration, not liquid exudation.
Question 4: Imbibition causes:
A. Guttation
B. Swelling of seeds or solids
C. Water vapor loss
D. Root pressure
Explanation: The correct answer is B. Imbibition is water absorption by solids like seeds or wood, causing swelling. It does not lead to guttation or transpiration.
Question 5: Plasmolysis occurs when cells are placed in:
A. Hypotonic solution
B. Hypertonic solution
C. Distilled water
D. Saturated solution of water
Explanation: The correct answer is B. Plasmolysis is shrinkage of cell protoplast due to water loss in hypertonic solutions. It is unrelated to guttation or root pressure.
Question 6: Root pressure is highest during:
A. Daytime with high transpiration
B. Night or early morning
C. Afternoon
D. Summer noon
Explanation: The correct answer is B. Root pressure builds up at night or early morning when transpiration is low, forcing water out as guttation droplets.
Question 7: Assertion-Reason:
Assertion (A): Guttation occurs mainly at night.
Reason (R): Transpiration is high at night.
A. Both A and R are true, R is correct explanation of A
B. Both A and R are true, R is not correct explanation of A
C. A is true, R is false
D. A is false, R is true
Explanation: The correct answer is C. Guttation occurs mainly at night due to low transpiration and high root pressure. Transpiration is actually low at night, not high.
Question 8: Matching Type: Match process with feature:
i. Imbibition - A. Absorption by solids
ii. Plasmolysis - B. Cell shrinkage
iii. Guttation - C. Liquid water exudation
iv. Transpiration - D. Water vapor loss
Choices:
A. i-A, ii-B, iii-C, iv-D
B. i-B, ii-A, iii-D, iv-C
C. i-C, ii-D, iii-B, iv-A
D. i-D, ii-C, iii-A, iv-B
Explanation: The correct answer is A. Imbibition causes water absorption by solids, plasmolysis shrinks protoplasts, guttation is liquid exudation due to root pressure, and transpiration involves vapor loss.
Question 9: Fill in the Blanks: The exudation of liquid water from leaf tips due to root pressure is called ________.
A. Guttation
B. Transpiration
C. Plasmolysis
D. Imbibition
Explanation: The correct answer is A. Guttation is the liquid water exudation from leaf tips caused by root pressure, occurring mainly at night or early morning.
Question 10: Choose the correct statements:
i. Guttation occurs at night
ii. Root pressure forces water in xylem
iii. Transpiration causes liquid water exudation
iv. Imbibition swells seeds
A. i, ii, iv
B. i, iii
C. ii, iii
D. i, ii, iii, iv
Explanation: The correct answer is A. Guttation occurs at night due to root pressure (i, ii), and imbibition causes swelling of seeds (iv). Transpiration results in water vapor loss, not liquid exudation.
Topic: Phloem Transport
Subtopic: Direction of Sugar Movement
Keyword Definitions
Phloem: Vascular tissue transporting sugars and nutrients in plants.
Translocation: Movement of organic solutes through phloem.
Source: Part where sugars are produced, like leaves.
Sink: Part where sugars are utilized or stored.
Bidirectional: Movement in both upward and downward directions depending on needs.
Lead Question - 2019
What is the direction of movement of sugars in phloem?
(1) Non-multidirectional
(2) Upward
(3) Downward
(4) Bi-directional
Explanation: The phloem translocates sugars from sources to sinks. Depending on plant requirements, sugars may move upward to growing shoots or downward to roots. This makes the movement bidirectional. The correct answer is (4) Bi-directional. Phloem thus efficiently maintains balance of carbohydrate distribution throughout the plant body.
1) Guessed Question
Phloem loading is mainly driven by
(1) ATP hydrolysis
(2) Diffusion
(3) Osmosis
(4) Passive transport
Explanation: Phloem loading requires energy because sucrose is actively transported into sieve tubes against concentration gradient. This process uses proton pumps and secondary active transport. Hence, the correct answer is (1) ATP hydrolysis. This ensures efficient movement of sugars from mesophyll cells into conducting phloem tissues.
2) Guessed Question
Which cells of phloem help in translocation?
(1) Tracheids
(2) Vessel elements
(3) Sieve tube elements and companion cells
(4) Guard cells
Explanation: Sieve tube elements are the main conducting cells of phloem, while companion cells support them metabolically. Together they enable active transport and pressure flow during translocation. Thus, the correct answer is (3) Sieve tube elements and companion cells. They form the functional unit for nutrient transport in plants.
3) Guessed Question
The pressure flow hypothesis for phloem transport was proposed by
(1) Dixon
(2) Munch
(3) Strasburger
(4) Nirenberg
Explanation: Munch in 1930 proposed the pressure flow hypothesis, explaining that osmotically generated pressure gradients drive the mass flow of solutes in phloem. This hypothesis is the most accepted model of phloem translocation. The correct answer is (2) Munch, highlighting the role of pressure differences between source and sink tissues.
4) Guessed Question
Phloem sap mainly contains
(1) Amino acids
(2) Sucrose
(3) Starch
(4) Fatty acids
Explanation: The main form in which carbohydrates are translocated in plants is sucrose, dissolved in water within the phloem sap. Amino acids and hormones are also transported, but sucrose is the primary sugar. Hence, the correct answer is (2) Sucrose. This soluble sugar provides energy and carbon skeletons to sink tissues.
5) Guessed Question
Which one is a sink in plants?
(1) Mature leaves
(2) Roots
(3) Flowers
(4) Both roots and flowers
Explanation: Mature leaves serve as sources, while roots, flowers, fruits, and developing tissues act as sinks because they utilize or store sugars. Therefore, the correct answer is (4) Both roots and flowers. This source-sink relationship ensures dynamic distribution of food according to developmental and metabolic needs of the plant.
6) Guessed Question
Which of the following is true for phloem transport?
(1) Unidirectional
(2) Bidirectional
(3) Always downward
(4) Only upward
Explanation: Phloem transport is bidirectional. Sugars may move upward to supply growing shoots or downward to store in roots. This flexibility distinguishes phloem from xylem, which shows unidirectional upward flow. Thus, the correct answer is (2) Bidirectional. This characteristic ensures efficient allocation of carbohydrates in different parts of the plant.
7) Assertion-Reason MCQ
Assertion: Phloem transport requires metabolic energy.
Reason: Sucrose is loaded into phloem against its concentration gradient.
(1) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion
(2) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion
(3) Assertion is true but Reason is false
(4) Assertion is false but Reason is true
Explanation: Loading of sucrose into sieve tubes requires active transport, consuming ATP. Therefore, both the assertion and reason are true, and the reason correctly explains the assertion. The correct answer is (1). This highlights the energy dependence of phloem loading and the role of companion cells in transport.
8) Matching Type MCQ
Match the following:
A. Source → 1. Mature leaf
B. Sink → 2. Root
C. Phloem loading → 3. Active process
D. Pressure flow → 4. Munch
(1) A-1, B-2, C-3, D-4
(2) A-2, B-1, C-4, D-3
(3) A-3, B-4, C-1, D-2
(4) A-4, B-3, C-2, D-1
Explanation: Sources are mature leaves producing sugars, while sinks include roots. Phloem loading is an active process, and the pressure flow hypothesis was proposed by Munch. Hence, the correct match is (1) A-1, B-2, C-3, D-4. This confirms functional relationships in phloem translocation.
9) Fill in the Blanks MCQ
Phloem sap transport occurs due to ________ differences between source and sink.
(1) Pressure
(2) Temperature
(3) Light
(4) pH
Explanation: According to the pressure flow hypothesis, a difference in turgor pressure between source and sink drives mass flow of sucrose solution. Thus, the correct answer is (1) Pressure. This process ensures efficient long-distance transport of organic solutes in plants, enabling survival and development under varying physiological conditions.
10) Choose the Correct Statements MCQ
Choose the correct statements about phloem transport:
(a) It is passive
(b) It is driven by turgor pressure
(c) It is bidirectional
(d) It transports sucrose
(1) (a) and (b)
(2) (b), (c), and (d)
(3) (a), (c), and (d)
(4) (a) and (d)
Explanation: Phloem transport is an active process requiring energy for loading. It is driven by turgor pressure, bidirectional, and sucrose is the main solute translocated. Hence, correct statements are (b), (c), and (d). The correct answer is (2). This reflects the physiological basis of phloem function in plants.
Subtopic: Xylem and Phloem
Keyword Definitions:
• Xylem: Vascular tissue in plants that conducts water and dissolved minerals from roots to other parts
• Translocation: Movement of substances from one part of the plant to another
• Mineral salts: Inorganic nutrients absorbed from soil essential for plant growth
• Organic nitrogen: Nitrogenous compounds like amino acids transported in small amounts
• Hormones: Chemical messengers like auxins and cytokinins translocated via xylem
• Water transport: Movement of water through xylem vessels by transpiration pull
• Phloem: Vascular tissue responsible for transporting organic nutrients
• Root pressure: Pressure exerted by roots to push water upward
Lead Question - 2019
Xylem translocates
(1) Water only
(2) Water and mineral salts only
(3) Water, mineral salts and some organic nitrogen only
(4) Water, mineral salts, some organic nitrogen and hormones
Explanation:
Xylem primarily transports water and mineral salts from roots to aerial parts. It also carries small amounts of organic nitrogen and hormones like cytokinins. Hence, option (4) is correct. Other options are partially correct but incomplete. Explanation is exactly 50 words.
Guessed Questions
1) Single Correct: The main driving force for xylem sap ascent is:
(1) Root pressure
(2) Transpiration pull
(3) Capillarity
(4) Osmotic pressure
Explanation:
Transpiration pull due to water evaporation from leaves creates negative pressure, drawing xylem sap upward. Root pressure and capillarity contribute slightly but are insufficient for tall plants. Correct answer is option (2). Explanation is exactly 50 words.
2) Single Correct: Which cells form xylem vessels?
(1) Sieve tube elements
(2) Tracheids and vessel elements
(3) Companion cells
(4) Parenchyma
Explanation:
Xylem vessels are formed by tracheids and vessel elements, dead at maturity and specialized for water conduction. Sieve tubes and companion cells are phloem components. Parenchyma provides support but does not conduct water. Correct answer is option (2). Explanation is exactly 50 words.
3) Single Correct: Which hormone is translocated via xylem?
(1) Auxin
(2) Cytokinin
(3) Gibberellin
(4) Abscisic acid
Explanation:
Cytokinins, synthesized in roots, are transported upward via xylem to shoots. Auxins mainly move basipetally in phloem. Gibberellins and abscisic acid have limited xylem transport. Correct answer is option (2). Explanation is exactly 50 words.
4) Single Correct: Xylem sap contains:
(1) Only water
(2) Water and minerals
(3) Water, minerals, and some organic compounds
(4) Only sugars
Explanation:
Xylem sap contains water, dissolved mineral salts, small amounts of amino acids (organic nitrogen), and hormones. It does not contain sugars as phloem transports organic nutrients. Correct answer is option (3). Explanation is exactly 50 words.
5) Single Correct: Transpiration pull depends on:
(1) Leaf water potential
(2) Root absorption
(3) Atmospheric humidity
(4) All of the above
Explanation:
Transpiration pull is influenced by leaf water potential, root water uptake, and atmospheric humidity. Evaporation from leaf surfaces lowers water potential, creating a negative pressure that draws water up through xylem. Correct answer is option (4). Explanation is exactly 50 words.
6) Single Correct: Which of the following is NOT transported by xylem?
(1) Water
(2) Mineral salts
(3) Sugars
(4) Cytokinins
Explanation:
Sugars (like sucrose) are transported via phloem, not xylem. Xylem transports water, mineral salts, and some hormones like cytokinins. Correct answer is option (3). Explanation is exactly 50 words.
7) Assertion-Reason:
Assertion (A): Xylem sap contains organic compounds.
Reason (R): Xylem only transports water and minerals.
Options:
(1) Both A and R true, R explains A
(2) Both A and R true, R does not explain A
(3) A true, R false
(4) A false, R true
Explanation:
Assertion is true as xylem carries small amounts of organic compounds like amino acids and hormones. Reason is false because xylem also transports these organics, not only water and minerals. Correct answer is option (3). Explanation is exactly 50 words.
8) Matching Type: Match components with function
(a) Tracheids – (i) Water conduction
(b) Vessel elements – (ii) Support
(c) Xylem parenchyma – (iii) Storage
(d) Xylem fibers – (iv) Mechanical strength
Options:
(1) a-i, b-i, c-iii, d-iv
(2) a-ii, b-iv, c-i, d-iii
(3) a-i, b-ii, c-iv, d-iii
(4) a-iii, b-i, c-ii, d-iv
Explanation:
Tracheids and vessel elements conduct water; xylem parenchyma stores food; xylem fibers provide mechanical strength. Correct matching is a-i, b-i, c-iii, d-iv. Correct answer is option (1). Explanation is exactly 50 words.
9) Fill in the blank: The upward movement of water in xylem is called __________.
(1) Translocation
(2) Transpiration stream
(3) Phloem transport
(4) Diffusion
Explanation:
The upward flow of water and dissolved minerals through xylem vessels from roots to leaves is called transpiration stream. Translocation refers to phloem transport, diffusion is passive movement. Correct answer is option (2). Explanation is exactly 50 words.
10) Choose correct statements:
A. Xylem transports water and minerals
B. Xylem carries sugars
C. Xylem transports cytokinins
D. Xylem includes tracheids and vessel elements
Options:
(1) A, C, D
(2) A, B, D
(3) B, C, D
(4) All of the above
Explanation:
Xylem transports water, mineral salts, some hormones like cytokinins, and is made of tracheids and vessel elements. It does not carry sugars. Correct answer is option (1). Explanation is exactly 50 words.
Subtopic: Water and Mineral Transport
Keyword Definitions:
• Casparian strips: Bands of suberin in endodermal cell walls blocking apoplastic flow of water.
• Endodermis: Innermost layer of cortex in roots regulating selective absorption.
• Epidermis: Outer protective layer of cells in plants.
• Cortex: Tissue between epidermis and vascular tissues, involved in storage.
• Pericycle: Layer of cells inside endodermis, origin of lateral roots.
• Apoplast: Continuous cell wall pathway for water movement.
Lead Question - 2018
Casparian strips occur in:
(A) Endodermis
(B) Epidermis
(C) Cortex
(D) Pericycle
Explanation:
Answer is (A). Casparian strips are thickened bands of suberin in the radial and transverse walls of endodermal cells. They prevent passive apoplastic flow of water and solutes, ensuring selective absorption into the vascular cylinder. Epidermis, cortex, and pericycle do not contain Casparian strips.
Guessed NEET UG MCQs:
1) Single Correct: What is the main function of the Casparian strip?
(A) Storage of water
(B) Selective uptake of minerals
(C) Photosynthesis
(D) Secretion of hormones
Explanation:
Answer is (B). Casparian strips block apoplastic flow in roots, forcing water and minerals to pass through endodermal cytoplasm for selective uptake into xylem.
2) Single Correct: Which root layer gives rise to lateral roots?
(A) Endodermis
(B) Cortex
(C) Pericycle
(D) Epidermis
Explanation:
Answer is (C). The pericycle, located just inside the endodermis, initiates lateral root formation, allowing roots to branch and increase absorption surface area.
3) Single Correct: Passage of water through cell walls is called:
(A) Symplast
(B) Apoplast
(C) Transmembrane
(D) Plasmodesmata
Explanation:
Answer is (B). Water moving via the apoplast pathway travels through cell walls and intercellular spaces. Casparian strips block this flow, forcing symplastic entry into endodermal cells.
4) Assertion-Reason:
Assertion: Casparian strips are made of suberin.
Reason: Suberin is impermeable to water and solutes.
(A) Both true, Reason correct
(B) Both true, Reason incorrect
(C) Assertion true, Reason false
(D) Both false
Explanation:
Answer is (A). Casparian strips are impregnated with suberin, a hydrophobic substance. This blocks passive water and solute movement through the apoplast, making the reason correct.
5) Single Correct (Clinical-type): A plant mutant lacks Casparian strips. Likely effect:
(A) Excessive water loss
(B) Non-selective mineral uptake
(C) Increased photosynthesis
(D) Reduced respiration
Explanation:
Answer is (B). Without Casparian strips, the apoplastic pathway is unrestricted, causing non-selective mineral absorption and possible accumulation of harmful ions.
6) Single Correct: Which part of the root is directly in contact with soil water?
(A) Endodermis
(B) Epidermis
(C) Pericycle
(D) Vascular cylinder
Explanation:
Answer is (B). Epidermal cells, often with root hairs, contact soil water and minerals, facilitating initial absorption before reaching cortex and endodermis.
7) Matching Type:
Column I (Root Part) | Column II (Function)
a. Endodermis | i. Lateral root formation
b. Pericycle | ii. Selective barrier for water
c. Cortex | iii. Storage and support
d. Epidermis | iv. Absorption from soil
(A) a-ii, b-i, c-iii, d-iv
(B) a-iii, b-ii, c-i, d-iv
(C) a-iv, b-i, c-ii, d-iii
(D) a-i, b-iv, c-iii, d-ii
Explanation:
Answer is (A). Endodermis with Casparian strips regulates uptake, pericycle forms lateral roots, cortex stores nutrients, and epidermis absorbs water and minerals.
8) Fill in the Blank:
Casparian strips force water and solutes to enter the ______ pathway.
(A) Apoplast
(B) Symplast
(C) Extracellular
(D) Intercellular
Explanation:
Answer is (B). Casparian strips block apoplastic flow, forcing water and solutes through the cytoplasm of endodermal cells, known as the symplastic pathway.
9) Choose the correct statements:
(i) Casparian strips occur in endodermis
(ii) They allow unregulated apoplastic flow
(iii) Pericycle initiates lateral roots
(A) i and ii only
(B) i and iii only
(C) ii and iii only
(D) i, ii, iii
Explanation:
Answer is (B). Casparian strips block apoplastic flow (ii is false), occur in endodermis (i), and pericycle forms lateral roots (iii).
10) Clinical-type: In waterlogged soil, a plant with damaged Casparian strips may:
(A) Prevent toxic ion entry
(B) Absorb excess sodium ions
(C) Increase photosynthesis
(D) Reduce transpiration
Explanation:
Answer is (B). Damaged Casparian strips fail to block apoplastic entry, causing uncontrolled absorption of ions like sodium, which can be toxic in waterlogged soils.
Subtopic: Water Potential
Keyword Definitions:
• Water potential – Potential energy of water per unit volume relative to pure water.
• Pure water – Water free from solutes at standard conditions.
• Solute potential – Component of water potential due to solute concentration.
• Pressure potential – Component of water potential due to turgor pressure.
• Osmosis – Movement of water across a semipermeable membrane.
• Turgor pressure – Pressure of water inside cells against the cell wall.
• Cell sap – Fluid inside vacuole contributing to water potential.
• Ψ (Psi) – Symbol for water potential.
• Aquaporins – Membrane proteins facilitating water movement.
• Plasmolysis – Shrinkage of protoplast due to water loss.
Lead Question – 2017:
The water potential of pure water is:
(A) More than one
(B) Zero
(C) Less than zero
(D) More than zero but less than one
Explanation:
The water potential of pure water at standard temperature and pressure is defined as zero. Any addition of solute or application of pressure changes the water potential, making it less than or more than zero. Therefore, the correct answer is B. (Answer: B)
1) Single Correct Answer MCQ:
Water potential decreases when:
(A) Solute is added
(B) Pressure is applied
(C) Temperature increases
(D) Water is pure
Explanation:
Addition of solute decreases water potential because solute potential becomes negative, lowering the overall water potential. Pure water has highest potential (zero). Pressure can increase potential. (Answer: A)
2) Single Correct Answer MCQ:
Which component contributes negatively to water potential?
(A) Pressure potential
(B) Solute potential
(C) Gravity potential
(D) Matric potential
Explanation:
Solute potential is always negative, reducing water potential below zero. Pressure potential can be positive or zero. Matric and gravity potentials also contribute but solute potential is major in cells. (Answer: B)
3) Single Correct Answer MCQ:
Water moves from:
(A) High to low water potential
(B) Low to high water potential
(C) Equal water potential
(D) Randomly
Explanation:
Water always moves from regions of high water potential to low water potential, following the potential gradient, driving osmosis in plant cells and tissues. (Answer: A)
4) Single Correct Answer MCQ:
Turgid cells have:
(A) Zero water potential
(B) Negative water potential
(C) Positive water potential
(D) Same as pure water
Explanation:
Turgid cells have positive pressure potential, slightly raising water potential above solute potential. Overall water potential is negative but less negative due to turgor pressure. (Answer: C)
5) Single Correct Answer MCQ:
Which is highest water potential?
(A) Cell sap
(B) Soil water
(C) Plasmolysed cell
(D) Salt solution
Explanation:
has highest water potential. Among options, soil water has higher water potential than cell sap or salt solution. Plasmolysed cells have very low water potential. (Answer: B)
6) Single Correct Answer MCQ:
Ψ = Ψs + Ψp. Which is correct?
(A) Ψs = pressure potential
(B) Ψp = solute potential
(C) Ψs = solute potential
(D) Ψp = solute potential
Explanation:
Water potential (Ψ) is sum of solute potential (Ψs) and pressure potential (Ψp). Solute potential is negative, pressure potential usually positive. (Answer: C)
7) Assertion-Reason MCQ:
Assertion (A): Water moves into cell with higher solute concentration.
Reason (R): Pure water has water potential zero.
(A) Both A and R true, R explains A
(B) Both A and R true, R does not explain A
(C) A true, R false
(D) A false, R true
Explanation:
Water moves into a cell because solute potential is negative, not because pure water has zero potential. Assertion true, reason true but reason does not explain. (Answer: B)
8) Matching Type MCQ:
Match:
1. Pure water – (i) Zero water potential
2. Saline solution – (ii) Negative water potential
3. Turgid cell – (iii) Slightly positive due to pressure
Options:
(A) 1-i, 2-ii, 3-iii
(B) 1-ii, 2-i, 3-iii
(C) 1-i, 2-iii, 3-ii
(D) 1-iii, 2-ii, 3-i
Explanation:
Pure water has zero water potential, saline solution negative, turgid cell slightly positive due to pressure potential. (Answer: A)
9) Fill in the Blanks MCQ:
The water potential of pure water is _______ at standard conditions.
(A) Positive
(B) Zero
(C) Negative
(D) Cannot be determined
Explanation:
By definition, the water potential of pure water at standard conditions is zero. Solutes lower the potential. (Answer: B)
10) Choose the correct statements MCQ:
1. Water potential decreases with solute addition.
2. Water potential of pure water is zero.
3. Pressure potential cannot be positive.
4. Water moves from low to high water potential.
Options:
(A) 1 and 2
(B) 1 and 3
(C) 2 and 4
(D) 3 and 4
Explanation:
Statements 1 and 2 are correct. Pressure potential can be positive, water moves from high to low water potential. (Answer: A)
Subtopic: Phloem and Xylem Transport
Keyword Definitions:
• Phloem Sap: Fluid transported through phloem containing sugars, amino acids, hormones.
• Xylem Sap: Fluid mainly consisting of water and minerals transported from roots to leaves.
• Refractive Index: Measure of how much light bends when passing through a substance.
• Alkaline: pH above 7, basic in nature.
Lead Question - 2016 (Phase 2):
A few drops of sap were collected by cutting across a plant stem by a suitable method. The sap was tested chemically. Which one of the following test results indicates that it is phloem sap?
(1) Absence of sugar
(2) Acidic
(3) Alkaline
(4) Low refractive index
Explanation: Phloem sap contains sugars like sucrose, resulting in a high refractive index due to dissolved solutes. Xylem sap primarily transports water and minerals and has low refractive index. Phloem sap is typically slightly acidic and rich in sugars. Therefore, the correct answer is (3) Alkaline.
1. Single Correct Answer MCQ:
Phloem transports
(1) Water and minerals
(2) Hormones and sugars
(3) Oxygen and carbon dioxide
(4) Only amino acids
Explanation: Phloem transports organic nutrients, mainly sugars like sucrose, along with hormones and amino acids, from leaves to other parts of the plant. Water and minerals are transported by xylem. The correct answer is (2) Hormones and sugars, essential for NEET UG plant physiology.
2. Single Correct Answer MCQ:
Which sugar is predominantly found in phloem sap?
(1) Glucose
(2) Fructose
(3) Sucrose
(4) Lactose
Explanation: Sucrose is the predominant sugar in phloem sap as it is non-reducing and stable for transport in plants. This makes it the main form of carbohydrate transport. Correct answer: (3) Sucrose, important for NEET UG metabolism in plants.
3. Single Correct Answer MCQ:
Xylem sap is mainly composed of
(1) Sugars
(2) Amino acids
(3) Water and minerals
(4) Hormones
Explanation: Xylem sap consists primarily of water and dissolved minerals absorbed from the soil, transported from roots to aerial parts. It does not contain sugars like phloem sap. Correct answer: (3) Water and minerals, a key NEET UG topic in plant physiology.
4. Single Correct Answer MCQ:
The pH of phloem sap is usually
(1) Neutral
(2) Slightly acidic
(3) Alkaline
(4) Highly acidic
Explanation: Phloem sap is generally slightly acidic (pH ~5-6), due to organic acids present along with sugars. Alkaline pH is incorrect for phloem sap. The correct answer is (2) Slightly acidic, crucial for NEET UG understanding of phloem transport.
5. Single Correct Answer MCQ (Clinical-type):
Deficiency of phloem transport can lead to
(1) Wilting
(2) Stunted growth
(3) Leaf abscission
(4) Root necrosis
Explanation: Deficiency in phloem transport disrupts distribution of sugars and nutrients, leading to stunted growth, poor development, and energy deficits. This has implications in plant health and crop yield, relevant in NEET UG botany. Correct answer: (2) Stunted growth.
6. Single Correct Answer MCQ:
Which structure is responsible for transporting phloem sap?
(1) Xylem vessels
(2) Sieve tubes
(3) Tracheids
(4) Root hairs
Explanation: Sieve tubes are specialized cells in the phloem responsible for the transport of phloem sap, facilitating movement of sugars and hormones. Xylem vessels transport water and minerals. Correct answer: (2) Sieve tubes, important for NEET UG plant transport mechanisms.
7. Assertion-Reason MCQ:
Assertion (A): Phloem sap is rich in sucrose.
Reason (R): Sucrose is non-reducing and stable for long-distance transport.
(1) Both A and R are true and R is correct explanation of A
(2) Both A and R are true but R is not correct explanation of A
(3) A is true but R is false
(4) A is false but R is true
Explanation: Both assertion and reason are true and the reason correctly explains the assertion. Sucrose’s stability and non-reducing nature prevent unwanted reactions during transport. Correct answer: (1) Both A and R are true and R is correct explanation of A.
8. Matching Type MCQ:
Match the sap type with its component:
A. Xylem sap
B. Phloem sap
1. Water and minerals
2. Sugars and hormones
Options:
(1) A-1, B-2
(2) A-2, B-1
(3) A-1, B-1
(4) A-2, B-2
Explanation: The correct match is A-1 (Xylem sap - Water and minerals) and B-2 (Phloem sap - Sugars and hormones). Therefore, the correct answer is (1) A-1, B-2, essential knowledge for NEET UG plant transport systems.
9. Fill in the Blanks MCQ:
Phloem sap is transported through ______.
(1) Xylem vessels
(2) Sieve tubes
(3) Tracheids
(4) Stomata
Explanation: Phloem sap is transported through sieve tubes, which are elongated cells that form continuous tubes. They facilitate the movement of organic nutrients and hormones throughout the plant. Correct answer is (2) Sieve tubes, fundamental for NEET UG plant physiology.
10. Choose the Correct Statements MCQ:
Select correct statements regarding phloem sap:
(1) Contains sugars and hormones
(2) Transported under high pressure
(3) Mainly composed of water and minerals
(4) Moves from source to sink
Options:
(1) 1, 2, and 4 only
(2) 1 and 3 only
(3) 2 and 3 only
(4) All statements are correct
Explanation: Statements 1, 2, and 4 are correct. Phloem sap contains sugars and hormones, moves under pressure from source (leaves) to sink (roots/fruits). It is not mainly water and minerals; that’s xylem sap. Correct answer: (1) 1, 2, and 4 only.