Topic: Nitrogen Metabolism; Subtopic: Nitrogen Cycle and Microbial Roles
Keyword Definitions:
Nitrogen Cycle: A biochemical cycle involving conversion of nitrogen and nitrogen-containing compounds in nature.
Ammonification: Process of decomposition of organic nitrogen into ammonia by microbes.
Nitrification: Oxidation of ammonia to nitrite and then nitrate by nitrifying bacteria.
Denitrification: Reduction of nitrates to gaseous nitrogen by bacteria like Thiobacillus.
Rhizobium: Symbiotic nitrogen-fixing bacterium living in root nodules of leguminous plants.
Nitrosomonas: Converts ammonia to nitrite during nitrification.
Nitrobacter: Converts nitrite (NO₂⁻) to nitrate (NO₃⁻).
Nitrococcus: Performs nitrification by oxidizing ammonia to nitrite.
Lead Question - 2023 (Manipur)
Match List - I with List - II
List - I List - II
(A) Nitrococcus (I) Denitrification
(B) Rhizobium (II) Conversion of ammonia to nitrite
(C) Thiobacillus (III) Conversion of nitrite to nitrate
(D) Nitrobacter (IV) Conversion of atmospheric nitrogen to ammonia
Choose the correct answer from the options given below:
Options: (A) (B) (C) (D)
1. III I IV II
2. IV III II I
3. II IV I III
4. I II III IV
Explanation:
Nitrococcus oxidizes ammonia to nitrite (II), Rhizobium fixes atmospheric nitrogen to ammonia (IV), Thiobacillus performs denitrification (I), and Nitrobacter oxidizes nitrite to nitrate (III). Hence, the correct sequence is (A-II), (B-IV), (C-I), (D-III). The correct answer is option 3. This matching shows the roles of microbes in nitrogen transformation during the nitrogen cycle.
Guessed Questions:
1. Single Correct Answer Type:
Which bacterium is responsible for converting nitrite (NO₂⁻) into nitrate (NO₃⁻)?
1. Nitrosomonas
2. Nitrococcus
3. Nitrobacter
4. Rhizobium
Explanation:
Nitrobacter is the nitrifying bacterium that oxidizes nitrite (NO₂⁻) into nitrate (NO₃⁻). This step completes the nitrification process and ensures nitrogen is available to plants in usable form. Therefore, Nitrobacter plays a crucial role in the nitrogen cycle. Correct answer: Nitrobacter.
2. Single Correct Answer Type:
Which of the following processes releases nitrogen gas (N₂) back into the atmosphere?
1. Nitrification
2. Ammonification
3. Denitrification
4. Nitrogen fixation
Explanation:
Denitrification converts nitrates or nitrites into gaseous nitrogen (N₂), releasing it into the atmosphere. Bacteria such as Thiobacillus and Pseudomonas perform this process in anaerobic conditions, maintaining nitrogen balance in ecosystems. Hence, the correct answer is denitrification.
3. Single Correct Answer Type:
Which bacterium is symbiotic in legume root nodules and fixes atmospheric nitrogen?
1. Azotobacter
2. Nitrosomonas
3. Rhizobium
4. Nitrococcus
Explanation:
Rhizobium is a symbiotic bacterium that inhabits the root nodules of leguminous plants. It converts atmospheric nitrogen into ammonia, making it available for plant protein synthesis. Thus, the correct answer is Rhizobium.
4. Single Correct Answer Type:
Which of the following reactions is carried out by Nitrosomonas?
1. NH₃ → NO₂⁻
2. NO₂⁻ → NO₃⁻
3. N₂ → NH₃
4. NO₃⁻ → N₂
Explanation:
Nitrosomonas oxidizes ammonia (NH₃) into nitrite (NO₂⁻) during the nitrification process. This is the first step of converting ammonia-based nitrogen into a more oxidized form. Therefore, the correct answer is NH₃ → NO₂⁻.
5. Single Correct Answer Type:
Which process is carried out by both free-living and symbiotic bacteria?
1. Denitrification
2. Nitrogen fixation
3. Nitrification
4. Ammonification
Explanation:
Nitrogen fixation can be carried out by free-living bacteria like Azotobacter and symbiotic bacteria like Rhizobium. They convert atmospheric nitrogen (N₂) into ammonia (NH₃), which can be used by plants for amino acid synthesis. Hence, the correct answer is nitrogen fixation.
6. Single Correct Answer Type:
During nitrification, which two bacterial genera are mainly involved?
1. Nitrosomonas and Nitrobacter
2. Rhizobium and Azospirillum
3. Thiobacillus and Nitrococcus
4. Azotobacter and Clostridium
Explanation:
In nitrification, Nitrosomonas oxidizes ammonia to nitrite, and Nitrobacter converts nitrite to nitrate. This two-step process supplies plants with nitrate, an essential nitrogen source for growth. Thus, the correct answer is Nitrosomonas and Nitrobacter.
7. Assertion-Reason Type:
Assertion (A): Rhizobium forms nodules in legume roots.
Reason (R): These nodules contain nitrogenase enzyme for nitrogen fixation.
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 statements are true, and R correctly explains A. Rhizobium induces nodule formation in leguminous roots, where nitrogenase enzyme catalyzes nitrogen fixation. Therefore, the correct answer is option 1.
8. Matching Type:
Match the following microorganisms with their functions:
A. Nitrosomonas — 1. Denitrification
B. Rhizobium — 2. Nitrogen fixation
C. Nitrobacter — 3. Converts nitrite to nitrate
D. Thiobacillus — 4. Converts ammonia to nitrite
1. A-4, B-2, C-3, D-1
2. A-1, B-3, C-2, D-4
3. A-3, B-1, C-4, D-2
4. A-2, B-4, C-1, D-3
Explanation:
Nitrosomonas converts ammonia to nitrite (4), Rhizobium fixes nitrogen (2), Nitrobacter converts nitrite to nitrate (3), and Thiobacillus performs denitrification (1). Correct matching: A-4, B-2, C-3, D-1.
9. Fill in the Blanks:
During nitrogen fixation, the enzyme ______ catalyzes the reduction of N₂ to NH₃.
1. Nitrate reductase
2. Nitrogenase
3. Nitrite reductase
4. Ammonase
Explanation:
Nitrogenase enzyme catalyzes the conversion of atmospheric nitrogen (N₂) into ammonia (NH₃) in the presence of ATP and reducing power. It is highly oxygen-sensitive and occurs in root nodules of legumes. Hence, the correct answer is nitrogenase.
10. Choose the Correct Statements:
Statement I: Denitrification converts ammonia into nitrate.
Statement II: Nitrification converts ammonia to nitrite and nitrate.
1. Both are true
2. Both are false
3. Statement I false, II true
4. Statement I true, II false
Explanation:
Denitrification reduces nitrate to nitrogen gas, not ammonia. Nitrification involves oxidation of ammonia to nitrite and nitrate by nitrifying bacteria. Thus, Statement I is false and Statement II is true. Correct answer: option 3.
Topic: Essential Mineral Elements; Subtopic: Mobility and Function of Mineral Nutrients
Keyword Definitions:
Remobilization: The process by which nutrients are withdrawn from older tissues and transported to younger, actively growing tissues.
Essential Elements: Elements required for plant growth, metabolism, and reproduction, which cannot be substituted by others.
Macronutrients: Nutrients required in large amounts, such as nitrogen, potassium, and calcium.
Micronutrients: Nutrients needed in small quantities like zinc, iron, and copper.
Deficiency Symptoms: Visual indicators of nutrient deficiency in plants like chlorosis, necrosis, or stunted growth.
Lead Question - 2023 (Manipur)
Which of the following mineral ion is not remobilized in plants?
1. Potassium
2. Calcium
3. Nitrogen
4. Phosphorus
Explanation: In plants, elements like nitrogen, phosphorus, and potassium are highly mobile and can move from older leaves to younger parts when needed. However, calcium is immobile once deposited in the cell wall and cannot be remobilized. Hence, deficiency symptoms of calcium first appear in young leaves. The correct answer is Calcium. This immobility arises because calcium binds tightly in pectate form within middle lamella, making it unavailable for translocation to new tissues.
Guessed Questions:
1. Which of the following nutrients is required for the synthesis of chlorophyll?
1. Nitrogen
2. Sulphur
3. Calcium
4. Phosphorus
Explanation: Nitrogen is a major component of amino acids, proteins, and chlorophyll. Its deficiency leads to yellowing of older leaves due to chlorosis. Being mobile, nitrogen can be remobilized from older tissues to younger ones during scarcity. Hence, the correct answer is nitrogen, crucial for photosynthesis and plant growth.
2. The element involved in the opening and closing of stomata is:
1. Magnesium
2. Potassium
3. Calcium
4. Iron
Explanation: Potassium ions regulate turgor pressure in guard cells, facilitating stomatal movement. During stomatal opening, potassium enters guard cells, drawing water in and causing them to swell. When potassium exits, stomata close. Thus, potassium plays a key role in water regulation and gaseous exchange in plants. Correct answer is potassium.
3. Which mineral deficiency causes chlorosis in plants?
1. Iron
2. Sulphur
3. Phosphorus
4. Molybdenum
Explanation: Chlorosis, the yellowing of leaves, results from reduced chlorophyll formation, commonly due to iron deficiency. Iron is immobile, so symptoms first appear in young leaves. It plays a vital role in chlorophyll biosynthesis and electron transport. Hence, the correct answer is iron, an essential micronutrient for green pigmentation.
4. The main function of magnesium in plants is:
1. Formation of cell wall
2. Activation of enzymes
3. Component of chlorophyll
4. Both 2 and 3
Explanation: Magnesium is the central atom in the chlorophyll molecule and also acts as an enzyme activator in photosynthesis, respiration, and nucleic acid synthesis. Its deficiency leads to interveinal chlorosis. Thus, the correct answer is both enzyme activation and chlorophyll formation, i.e., option 4.
5. Which mineral element is a constituent of amino acids cysteine and methionine?
1. Nitrogen
2. Sulphur
3. Iron
4. Potassium
Explanation: Sulphur forms part of sulphur-containing amino acids like cysteine, cystine, and methionine, essential for protein structure and function. It also occurs in coenzymes and vitamins like biotin and thiamine. Sulphur deficiency causes yellowing of young leaves. The correct answer is sulphur, crucial for protein synthesis.
6. Which of the following is an immobile nutrient?
1. Nitrogen
2. Phosphorus
3. Calcium
4. Potassium
Explanation: Calcium is an immobile nutrient that cannot move from older to younger tissues once deposited in cell walls. Its deficiency affects growing points, leading to necrosis and deformation. This characteristic distinguishes it from mobile nutrients like nitrogen and potassium. Therefore, the correct answer is calcium.
7. Assertion-Reason:
Assertion (A): Calcium deficiency leads to death of shoot tips.
Reason (R): Calcium is immobile and required for cell wall stability and membrane integrity.
Options:
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: Calcium strengthens cell walls and membranes. Since it is immobile, its deficiency severely affects meristematic tissues like shoot tips, causing their death. Thus, both A and R are true, and R correctly explains A. The correct answer is option 1.
8. Matching Type:
Match the elements with their functions:
(A) Nitrogen → (i) Activation of enzymes
(B) Potassium → (ii) Opening of stomata
(C) Calcium → (iii) Cell wall formation
(D) Sulphur → (iv) Component of proteins
Options:
1. A-(iv), B-(ii), C-(iii), D-(i)
2. A-(i), B-(ii), C-(iv), D-(iii)
3. A-(iv), B-(i), C-(ii), D-(iii)
4. A-(iii), B-(ii), C-(i), D-(iv)
Explanation: Nitrogen is part of amino acids, potassium regulates stomata, calcium forms cell walls, and sulphur is found in proteins. Hence, the correct match is A-(iv), B-(ii), C-(iii), D-(i). These minerals perform distinct biochemical roles essential for growth and metabolism.
9. Fill in the Blanks:
Deficiency of nitrogen causes ______ in older leaves.
1. Necrosis
2. Chlorosis
3. Purpling
4. Wilting
Explanation: Nitrogen deficiency results in chlorosis, characterized by yellowing of older leaves due to reduced chlorophyll synthesis. Being a mobile element, nitrogen moves to younger tissues during scarcity, leaving older ones deficient. Therefore, the correct answer is chlorosis, commonly seen in nitrogen-starved plants like maize and wheat.
10. Choose the Correct Statements:
Statement I: Calcium is a mobile element in plants.
Statement II: Deficiency of calcium first appears in young leaves.
1. Both statements are true.
2. Both statements are false.
3. Statement I is false, Statement II is true.
4. Statement I is true, Statement II is false.
Explanation: Calcium is immobile, and its deficiency affects young tissues first due to inability to move from older parts. Hence, Statement I is false and Statement II is true. The correct answer is option 3. Calcium plays vital roles in cell wall stabilization and signaling.
Keyword Definitions:
Iron (Fe): Essential micronutrient; component of enzymes like catalase and cytochromes.
Zinc (Zn): Cofactor in several enzymes; involved in auxin synthesis, protein metabolism.
Boron (B): Essential for cell wall formation, cell elongation, and differentiation.
Molybdenum (Mo): Component of enzymes like nitrate reductase; important in nitrogen metabolism.
Auxin: Plant hormone controlling growth, cell elongation, and differentiation.
Catalase: Enzyme that breaks down hydrogen peroxide, protecting cells from oxidative damage.
Nitrate reductase: Enzyme converting nitrate to nitrite during nitrogen assimilation.
Micronutrients: Essential elements required in small quantities for plant growth and metabolism.
Cell elongation: Increase in cell length, regulated by hormones and nutrients.
Differentiation: Process by which cells acquire specific functions and structures.
Enzyme activator: Substance that increases the activity of an enzyme.
Lead Question - 2023:
Match List I with List II :
List - I List - II
A. Iron I. Synthesis of auxin
B. Zinc II. Component of nitrate reductase
C. Boron III. Activator of catalase
D. Molybdenum IV. Cell elongation and differentiation
Choose the correct answer from the option given below :
(1) A-III, B-I, C-IV, D-II
(2) A-II, B-IV, C-I, D-III
(3) A-III, B-II, C-I, D-IV
(4) A-II, B-III, C-IV, D-I
Answer & Explanation: (1) A-III, B-I, C-IV, D-II. Iron acts as an activator of catalase and other enzymes, Zinc is involved in the synthesis of auxin which regulates growth, Boron supports cell elongation and differentiation, and Molybdenum is a cofactor of nitrate reductase necessary for nitrogen metabolism. These micronutrients play critical roles in enzymatic reactions, hormone synthesis, and structural development of plants. Proper availability ensures efficient metabolism, growth, and development. Deficiency in any of these elements leads to specific physiological disorders. Understanding these functions is crucial in plant physiology and agriculture.
1. Iron deficiency affects which enzyme activity?
(1) Nitrate reductase
(2) Catalase
(3) Amylase
(4) RNA polymerase
Explanation: Iron serves as an activator for catalase and other oxidoreductases. Deficiency reduces catalase activity, impairing hydrogen peroxide breakdown. Correct answer is (2).
2. Zinc in plants is mainly required for:
(1) Photosynthesis
(2) Auxin synthesis
(3) Nitrogen fixation
(4) Cell wall formation
Explanation: Zinc is a cofactor for enzymes involved in auxin synthesis, which regulates growth and development. Correct answer is (2).
3. Boron deficiency causes:
(1) Impaired chlorophyll synthesis
(2) Poor cell elongation and differentiation
(3) Reduced nitrate assimilation
(4) Increased catalase activity
Explanation: Boron is essential for cell wall integrity and cell elongation; deficiency leads to structural deformities. Correct answer is (2).
4. Molybdenum is essential for:
(1) Nitrogen metabolism
(2) Photosystem II activity
(3) Sugar transport
(4) Ethylene production
Explanation: Molybdenum is a component of nitrate reductase, crucial for nitrate reduction in nitrogen metabolism. Correct answer is (1).
5. Micronutrients are required in:
(1) Large quantities
(2) Trace amounts
(3) Equal amounts as macronutrients
(4) Only during flowering
Explanation: Micronutrients like Fe, Zn, B, Mo are required in trace amounts for enzymatic and metabolic functions. Correct answer is (2).
6. Activator of catalase is:
(1) Zinc
(2) Boron
(3) Iron
(4) Molybdenum
Explanation: Iron acts as a cofactor and activator of catalase enzyme, enhancing hydrogen peroxide breakdown. Correct answer is (3).
Assertion-Reason Type Question
7. Assertion (A): Zinc deficiency reduces auxin synthesis.
Reason (R): Zinc is a cofactor for enzymes involved in auxin biosynthesis.
(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: Zinc is necessary for enzymes catalyzing auxin synthesis. Its deficiency leads to stunted growth due to reduced auxin. Correct answer is (1).
Matching Type Question
8. Match micronutrient with deficiency symptom:
A. Iron – (i) Interveinal chlorosis
B. Zinc – (ii) Stunted growth
C. Boron – (iii) Poor cell wall development
D. Molybdenum – (iv) Accumulation of nitrate
(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: Iron deficiency causes interveinal chlorosis, zinc deficiency stunts growth, boron deficiency impairs cell wall, molybdenum deficiency leads to nitrate accumulation. Correct answer is (1).
Fill in the Blanks Question
9. ______ is a component of nitrate reductase enzyme.
(1) Iron
(2) Zinc
(3) Molybdenum
(4) Boron
Explanation: Molybdenum is an essential cofactor for nitrate reductase, enabling nitrate reduction during nitrogen metabolism. Correct answer is (3).
Choose the Correct Statements Question
10. Statement I: Boron regulates cell elongation.
Statement II: Iron activates catalase.
(1) Both I and II correct
(2) Only I correct
(3) Only II correct
(4) Neither I nor II correct
Explanation: Boron is essential for cell wall formation and elongation, while iron acts as an activator of catalase enzyme. Correct answer is (1).
Topic: Essential Elements; Subtopic: Micronutrients in Photosynthesis
Keyword Definitions:
Micronutrients: Essential elements required by plants in very small quantities for normal growth and metabolism.
Photosynthesis: The process by which green plants use sunlight to synthesize food from carbon dioxide and water.
Light Reaction: The phase of photosynthesis occurring in thylakoid membranes where light energy is converted into chemical energy (ATP and NADPH).
Oxygen Evolution: The release of oxygen during the photolysis of water in photosystem II.
Manganese and Chlorine: Essential micronutrients involved in the splitting of water molecules during photosynthesis.
Lead Question - 2022 (Abroad)
Which of the following pair of micronutrients would help in the light phase of photosynthesis to help in the reaction leading to oxygen evolution?
1. Zinc and Chlorine
2. Manganese and Molybdenum
3. Molybdenum and Iron
4. Manganese and Chlorine
Explanation: The light phase of photosynthesis involves the photolysis of water, which leads to oxygen evolution. The oxygen-evolving complex (OEC) of photosystem II requires manganese (Mn) and chlorine (Cl) ions as cofactors for splitting water molecules into protons, electrons, and oxygen. Hence, the correct answer is option 4 — Manganese and Chlorine.
1. Manganese plays an important role in:
1. Activation of nitrogenase enzyme
2. Splitting of water to release oxygen
3. Formation of chlorophyll pigment
4. Reduction of nitrates to ammonia
Explanation: Manganese (Mn) acts as a cofactor in the oxygen-evolving complex (OEC) of photosystem II. It facilitates the splitting of water molecules into protons, electrons, and oxygen during the light reaction of photosynthesis. Hence, the correct answer is option 2 — Splitting of water to release oxygen.
2. Chlorine deficiency in plants results in:
1. Reduced oxygen evolution and leaf wilting
2. Increased nitrate accumulation
3. Enhanced chlorophyll synthesis
4. Excessive transpiration
Explanation: Chlorine (Cl⁻) helps in maintaining osmotic balance and acts as an essential ion in the oxygen-evolving complex of photosystem II. Its deficiency reduces oxygen evolution, leading to wilting and chlorosis. Therefore, the correct answer is option 1 — Reduced oxygen evolution and leaf wilting.
3. The oxygen-evolving complex (OEC) is associated with:
1. Photosystem I
2. Photosystem II
3. Calvin cycle
4. Glycolysis
Explanation: The oxygen-evolving complex (OEC) or water-splitting complex is part of photosystem II, located on the inner surface of the thylakoid membrane. It catalyzes the photolysis of water to release oxygen, protons, and electrons. Hence, the correct answer is option 2 — Photosystem II.
4. Which of the following micronutrients is involved in nitrogen metabolism rather than oxygen evolution?
1. Manganese
2. Molybdenum
3. Chlorine
4. Iron
Explanation: Molybdenum (Mo) acts as a cofactor for nitrate reductase and nitrogenase enzymes, helping in nitrogen reduction and fixation. It is not directly involved in the oxygen-evolving complex of photosynthesis. Hence, the correct answer is option 2 — Molybdenum.
5. The splitting of water molecules during photosynthesis provides:
1. ATP
2. NADPH
3. Protons, electrons, and oxygen
4. Glucose and CO₂
Explanation: During the light reaction of photosynthesis, water is split by the oxygen-evolving complex in photosystem II into protons (H⁺), electrons (e⁻), and oxygen (O₂). This process provides electrons for photosynthetic electron transport and contributes to proton gradient formation. Hence, the correct answer is option 3.
6. Which pair of elements are directly required for photolysis of water in chloroplasts?
1. Mn and Cl
2. Fe and Mo
3. Zn and Cu
4. Mg and K
Explanation: The photolysis of water requires manganese (Mn) and chloride (Cl) ions as essential cofactors in the oxygen-evolving complex (OEC) of photosystem II. These elements help in the oxidation of water molecules, leading to oxygen evolution. Hence, the correct answer is option 1 — Mn and Cl.
7. Assertion (A): Manganese and Chlorine are required for oxygen evolution in plants.
Reason (R): They form part of the oxygen-evolving complex in photosystem II.
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: Manganese and Chlorine ions are essential for the oxygen-evolving complex (OEC) of photosystem II, which catalyzes the photolysis of water, releasing oxygen. Both statements are true, and the reason correctly explains the assertion. Hence, the correct answer is option 1.
8. Match the following:
A. Manganese — (i) Oxygen-evolving complex
B. Molybdenum — (ii) Nitrate reductase
C. Iron — (iii) Electron transport chain
1. A-(i), B-(ii), C-(iii)
2. A-(ii), B-(i), C-(iii)
3. A-(iii), B-(ii), C-(i)
4. A-(i), B-(iii), C-(ii)
Explanation: Manganese participates in oxygen evolution in PS II, Molybdenum in nitrate reduction, and Iron in electron transport during photosynthesis. Hence, the correct matching is A-(i), B-(ii), C-(iii), corresponding to option 1.
9. Fill in the blank:
The oxygen-evolving complex of photosystem II contains __________ ions essential for splitting of water.
1. Iron
2. Molybdenum
3. Manganese and Chlorine
4. Zinc and Copper
Explanation: The oxygen-evolving complex (OEC) consists of manganese and chloride ions that are critical for the photolysis of water molecules in photosystem II. These ions help stabilize the complex and enable the release of oxygen. Hence, the correct answer is option 3.
10. Choose the correct statements:
1. Manganese and Chlorine are involved in water splitting.
2. Iron is part of chlorophyll structure.
3. Molybdenum helps in nitrogen fixation.
4. Zinc acts as a cofactor for carbonic anhydrase.
Explanation: All four statements are scientifically correct. Manganese and Chlorine assist in oxygen evolution, Iron aids in electron transport, Molybdenum assists in nitrogen metabolism, and Zinc activates carbonic anhydrase for CO₂ fixation. Therefore, the correct answer is option 1, 2, 3, and 4 — all are correct.
Subtopic: Role of Micronutrients and Macronutrients
Keyword Definitions:
Manganese: Micronutrient involved in enzyme activation and splitting of water during photosynthesis.
Magnesium: Central atom of chlorophyll, also activates enzymes for respiration and photosynthesis.
Boron: Essential for cell wall formation and required for pollen germination.
Iron: Micronutrient involved in electron transport and enzyme activation, essential for chlorophyll synthesis.
Enzyme activation: The process where minerals help enzymes perform biochemical reactions efficiently.
Photosynthesis: Process by which plants convert light energy into chemical energy.
Pollen germination: The process of pollen tube formation for fertilization.
Respiration enzymes: Enzymes involved in breakdown of glucose to release energy.
Micronutrients: Nutrients required in small quantities for plant growth and development.
Macronutrients: Nutrients required in larger amounts such as N, P, K, Ca, Mg, S.
Lead Question (2022)
Match List - I with List - II
List - I | List - II
(a) Manganese — (i) Activates the enzyme catalase
(b) Magnesium — (ii) Required for pollen germination
(c) Boron — (iii) Activates enzymes of respiration
(d) Iron — (iv) Functions in splitting of water during photosynthesis
Choose the correct answer from the option given below:
(1) (a) - (iv), (b) - (iii), (c) - (ii), (d) - (i)
(2) (a) - (iv), (b) - (i), (c) - (ii), (d) - (iii)
(3) (a) - (iii), (b) - (i), (c) - (ii), (d) - (iv)
(4) (a) - (iii), (b) - (iv), (c) - (i), (d) - (ii)
Explanation:
Manganese functions in the splitting of water during photosynthesis, Magnesium activates enzymes of respiration, Boron is essential for pollen germination, and Iron activates catalase. Therefore, the correct matching is (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i). Correct answer is (1).
1. Single Correct Answer MCQ:
Which micronutrient is essential for pollen germination?
(1) Magnesium
(2) Boron
(3) Iron
(4) Manganese
Explanation:
Boron is crucial for pollen germination and reproductive processes in plants. Magnesium, Iron, and Manganese have other roles in enzyme activation and photosynthesis. Correct answer is (2).
2. Single Correct Answer MCQ:
Which element helps in splitting water during photosynthesis?
(1) Magnesium
(2) Manganese
(3) Boron
(4) Iron
Explanation:
Manganese participates in the water-splitting reaction of photosystem II during photosynthesis, producing electrons, protons, and oxygen. Correct answer is (2).
3. Single Correct Answer MCQ:
Which mineral activates catalase enzyme?
(1) Iron
(2) Boron
(3) Magnesium
(4) Manganese
Explanation:
Iron activates catalase, which decomposes hydrogen peroxide into water and oxygen. Other minerals serve different functions. Correct answer is (1).
4. Single Correct Answer MCQ:
Magnesium is essential because it:
(1) Splits water
(2) Activates respiration enzymes
(3) Activates catalase
(4) Aids pollen germination
Explanation:
Magnesium activates enzymes of respiration and is central to chlorophyll molecule. It is not directly involved in water splitting, catalase activation, or pollen germination. Correct answer is (2).
5. Single Correct Answer MCQ:
Which of the following elements is part of the chlorophyll molecule?
(1) Boron
(2) Magnesium
(3) Manganese
(4) Iron
Explanation:
Magnesium forms the central atom of the chlorophyll molecule and is essential for photosynthesis. Correct answer is (2).
6. Single Correct Answer MCQ:
Which micronutrient is involved in enzyme activation of respiration?
(1) Magnesium
(2) Boron
(3) Iron
(4) Manganese
Explanation:
Magnesium activates enzymes of respiration by acting as a cofactor. Manganese, Iron, and Boron have other specialized functions. Correct answer is (1).
7. Assertion-Reason MCQ:
Assertion (A): Iron activates catalase enzyme.
Reason (R): Catalase is involved in breakdown of hydrogen peroxide.
Options:
(1) Both A and R correct, R explains A
(2) A correct, R incorrect
(3) A incorrect, R correct
(4) Both A and R incorrect
Explanation:
Iron activates catalase, which decomposes hydrogen peroxide into water and oxygen, reducing oxidative damage in cells. Both the assertion and reason are correct, and the reason explains the assertion. Correct answer is (1).
8. Matching Type MCQ:
Match element with its function:
A. Manganese — 1. Pollen germination
B. Magnesium — 2. Enzymes of respiration
C. Boron — 3. Splitting of water
D. Iron — 4. Catalase activation
Options:
(1) A–3, B–2, C–1, D–4
(2) A–2, B–3, C–4, D–1
(3) A–3, B–4, C–2, D–1
(4) A–4, B–2, C–1, D–3
Explanation:
Manganese functions in splitting water (3), Magnesium activates enzymes of respiration (2), Boron required for pollen germination (1), Iron activates catalase (4). Correct matching is (1).
9. Fill in the Blanks MCQ:
________ is required for splitting water during photosynthesis.
(1) Magnesium
(2) Manganese
(3) Iron
(4) Boron
Subtopic: Biological Nitrogen Fixation
Keyword Definitions:
Glycine max: Scientific name for soybean, a leguminous plant capable of nitrogen fixation.
Biological Nitrogen Fixation (BNF): Conversion of atmospheric nitrogen into ammonia by symbiotic bacteria.
Root nodules: Specialized structures on legume roots housing nitrogen-fixing bacteria.
Ammonia: NH3, initial product of nitrogen fixation in root nodules.
Glutamate: Amino acid formed by incorporation of ammonia into organic compounds.
Nitrates: NO3-, inorganic nitrogen form absorbed from soil.
Ureides: Nitrogen-rich compounds (allantoin, allantoic acid) transported in some legumes.
Transport: Movement of nitrogenous compounds from root nodules to leaves and other tissues.
Legumes: Plants that form symbiotic relationships with Rhizobium bacteria.
Symbiosis: Mutualistic relationship between two species, here Rhizobium and Glycine max.
Amino acid transport: Movement of nitrogen in organic forms to support growth and protein synthesis.
Lead Question - 2020 (COVID Reexam)
In Glycine max, the product of biological nitrogen fixation is transported from the root nodules to other parts as:
1. Ammonia
2. Glutamate
3. Nitrates
4. Ureides
Explanation: In Glycine max, nitrogen fixed by Rhizobium in root nodules is converted to ureides (allantoin and allantoic acid) for transport to other plant parts. This organic transport form allows efficient nitrogen distribution and assimilation in leaves and stems. Correct answer is option 4: Ureides. (50 words)
Guessed Question 1. Single Correct Answer MCQ: Which bacteria fix nitrogen in legume root nodules?
1. Escherichia coli
2. Rhizobium
3. Bacillus
4. Azotobacter
Explanation: Rhizobium species form symbiotic relationships with legumes, fixing atmospheric nitrogen into ammonia in root nodules. Free-living bacteria like Azotobacter also fix nitrogen but not in nodules. Correct answer is option 2: Rhizobium. Efficient nitrogen fixation supports growth and protein synthesis. (50 words)
Guessed Question 2. Single Correct Answer MCQ: Initial product of nitrogen fixation in nodules is :
1. Ureides
2. Ammonia
3. Nitrates
4. Nitrites
Explanation: Nitrogenase in Rhizobium converts atmospheric nitrogen to ammonia (NH3) in root nodules. This ammonia is subsequently converted into ureides or amino acids for transport. Correct answer is option 2: Ammonia. This step is critical in nitrogen assimilation and plant nutrition. (50 words)
Guessed Question 3. Single Correct Answer MCQ: Organic nitrogen transported from nodules in soybean is :
1. Glutamate
2. Ureides
3. Nitrates
4. Ammonium salts
Explanation: Soybean (Glycine max) transports nitrogen fixed in nodules as ureides, mainly allantoin and allantoic acid. This organic form is stable for long-distance transport to shoots and leaves. Correct answer is option 2: Ureides. Efficient transport ensures nitrogen availability for protein and nucleic acid synthesis. (50 words)
Guessed Question 4. Single Correct Answer MCQ: Nitrogen in the form of ureides moves from nodules to :
1. Roots only
2. Leaves and stems
3. Flowers only
4. Soil
Explanation: Ureides produced in root nodules are transported via xylem to leaves and stems, providing nitrogen for protein synthesis, nucleotides, and metabolic activities. Correct answer is option 2: Leaves and stems. This systemic transport supports growth and development in all aerial tissues. (50 words)
Guessed Question 5. Assertion-Reason MCQ:
Assertion (A): Glycine max transports nitrogen mainly as ureides.
Reason (R): Ammonia is toxic and converted to stable organic compounds for transport.
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: Nitrogen fixed as ammonia is converted into ureides for safe transport in soybean. Both the assertion and reason are true, and R correctly explains A. Correct answer is option 1. This mechanism prevents ammonia toxicity and ensures efficient nitrogen distribution. (50 words)
Guessed Question 6. Matching Type MCQ:
Column I - Function
(a) Rhizobium (i) Nitrogen fixation
(b) Root nodules (ii) Housing bacteria
(c) Ureides (iii) Nitrogen transport
(d) Glutamate (iv) Amino acid formation
Options:
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)-(iii), (b)-(i), (c)-(iv), (d)-(ii)
Explanation: Rhizobium fixes nitrogen, root nodules house bacteria, ureides transport nitrogen to shoots, and glutamate is formed from ammonia assimilation. Correct answer is option 1. These steps coordinate nitrogen fixation, assimilation, and distribution in soybean plants. (50 words)
Guessed Question 7. Fill in the blank:
In legumes like Glycine max, atmospheric nitrogen is converted to _______ by root nodules.
1. Ammonia
2. Nitrates
3. Nitrites
4. Ureides
Explanation: Atmospheric nitrogen is reduced to ammonia in root nodules, which is then incorporated into ureides for transport. Correct answer is option 1: Ammonia. This initial step is crucial for nitrogen assimilation and subsequent distribution in the plant. (50 words)
Guessed Question 8. Single Correct Answer MCQ: Ureides mainly include :
1. Ammonium salts
2. Allantoin and allantoic acid
3. Glutamine and glutamate
4. Nitrates
Explanation: Ureides in soybean consist of allantoin and allantoic acid, nitrogen-rich compounds synthesized from ammonia. Correct answer is option 2. They serve as the primary transport form of nitrogen from nodules to aerial plant parts for assimilation. (50 words)
Guessed Question 9. Single Correct Answer MCQ: Why is ammonia converted to ureides in soybean?
1. To increase toxicity
2. For stable long-distance transport
3. To form nitrates
4. For immediate excretion
Explanation: Ammonia is toxic; conversion to ureides provides
Topic: Nitrogen Metabolism
Subtopic: Biological Nitrogen Fixation
Nitrogenase: An enzyme complex in root nodules that reduces atmospheric nitrogen to ammonia.
Root Nodules: Swellings on legume roots hosting nitrogen-fixing bacteria like Rhizobium.
Leguminous Plants: Plants of the family Fabaceae capable of symbiotic nitrogen fixation.
Ammonia: NH3, the primary product of nitrogenase activity, usable by plants for amino acid synthesis.
Hydrogen: H2, a by-product of the nitrogenase reaction.
Atmospheric Nitrogen (N2): Nitrogen gas available in the air, converted to ammonia by nitrogenase.
Symbiosis: Mutualistic relationship between legume plants and nitrogen-fixing bacteria.
Rhizobium: A genus of bacteria forming nodules on legume roots and fixing nitrogen.
Nitrate: NO3-, a form of nitrogen available to plants but not directly produced by nitrogenase.
Enzyme Catalysis: Acceleration of a chemical reaction by a specific enzyme.
Biological Nitrogen Fixation: Conversion of atmospheric nitrogen to ammonia by microorganisms.
Lead Question (2020): The product(s) of reaction catalyzed by nitrogenase in root nodules of leguminous plants is/are:
Options:
1. Ammonia and oxygen
2. Ammonia and hydrogen
3. Ammonia alone
4. Nitrate alone
Explanation: Correct answer is 2. Nitrogenase catalyzes the reduction of atmospheric nitrogen (N2) to ammonia (NH3), producing hydrogen (H2) as a by-product. Oxygen is inhibitory for nitrogenase activity, and nitrate is not directly produced by this enzymatic reaction.
1. Single Correct Answer MCQ:
Which microorganism forms symbiotic nitrogen-fixing nodules in legumes?
Options:
a. Rhizobium
b. Azotobacter
c. Nitrosomonas
d. Clostridium
Explanation: Correct answer is a. Rhizobium bacteria form nodules on legume roots and perform symbiotic nitrogen fixation, producing ammonia for the host plant.
2. Single Correct Answer MCQ:
Nitrogenase is inhibited by:
Options:
a. Hydrogen
b. Oxygen
c. Ammonia
d. Carbon dioxide
Explanation: Correct answer is b. Oxygen irreversibly inactivates nitrogenase, so legume nodules maintain a low oxygen environment for effective nitrogen fixation.
3. Single Correct Answer MCQ:
The primary form of nitrogen directly available to plants from nitrogenase activity is:
Options:
a. Nitrate
b. Nitrite
c. Ammonia
d. Nitrogen gas
Explanation: Correct answer is c. Ammonia (NH3) produced by nitrogenase is assimilated into amino acids by the plant; nitrate is not directly produced in this enzymatic reaction.
4. Single Correct Answer MCQ:
Hydrogen produced during nitrogenase reaction is:
Options:
a. Main product
b. By-product
c. Inhibitor
d. Oxygen source
Explanation: Correct answer is b. Hydrogen gas (H2) is released as a by-product of the nitrogenase-catalyzed reduction of nitrogen to ammonia.
5. Single Correct Answer MCQ:
Which of the following is not involved in symbiotic nitrogen fixation?
Options:
a. Leguminous plant
b. Rhizobium
c. Mycorrhizal fungi
d. Root nodule
Explanation: Correct answer is c. Mycorrhizal fungi assist in phosphorus uptake, not nitrogen fixation, which is performed by Rhizobium in legume root nodules.
6. Single Correct Answer MCQ:
Which metal cofactor is essential for nitrogenase activity?
Options:
a. Magnesium
b. Iron and Molybdenum
c. Calcium
d. Zinc
Explanation: Correct answer is b. Nitrogenase requires iron and molybdenum as cofactors for electron transfer during the reduction of nitrogen to ammonia.
7. Assertion-Reason MCQ:
Assertion (A): Legume root nodules perform nitrogen fixation.
Reason (R): Nitrogenase enzyme reduces atmospheric nitrogen to ammonia.
Options:
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: Correct answer is a. Nitrogenase catalyzes nitrogen reduction, which enables legume nodules to fix atmospheric nitrogen into ammonia for plant nutrition.
8. Matching Type MCQ:
Match the following:
(a) Rhizobium - (i) Nitrogen-fixing bacteria
(b) Root Nodule - (ii) Site of nitrogen fixation
(c) Ammonia - (iii) Product of nitrogenase
Options:
1. a-i, b-ii, c-iii
2. a-ii, b-i, c-iii
3. a-iii, b-ii, c-i
4. a-i, b-iii, c-ii
Explanation: Correct answer is 1. Rhizobium is the nitrogen-fixing bacteria, root nodules are the site of fixation, and ammonia is the main product of nitrogenase activity.
9. Fill in the Blanks MCQ:
The enzyme responsible for converting atmospheric nitrogen to ammonia is ________.
Options:
a. Nitrate reductase
b. Nitrogenase
c. Nitrite oxidase
d. Glutamine synthetase
Explanation: Correct answer is b. Nitrogenase catalyzes the reduction of N2 to NH3 in legume root nodules.
10. Choose the correct statements MCQ:
Select correct statements regarding biological nitrogen fixation:
i. Rhizobium is
Topic: Essential Elements in Plants
Subtopic: Functions of Micronutrients
Essential Elements: Minerals required for normal growth, development, and reproduction of plants.
Iron (Fe): Micronutrient essential for chlorophyll biosynthesis and electron transport during photosynthesis.
Zinc (Zn): Micronutrient involved in auxin (IAA) synthesis and enzyme activation in plants.
Boron (B): Required for pollen germination, cell wall formation, and reproductive growth.
Manganese (Mn): Important for photolysis of water in photosystem II and other enzymatic activities.
Micronutrients: Elements required in small quantities, usually less than 100 mg/kg of plant tissue.
Photosystem II: Protein complex in chloroplasts responsible for water splitting and oxygen evolution.
Chlorophyll: Green pigment in plants responsible for light absorption during photosynthesis.
Pollen Germination: Process where pollen tube emerges to deliver sperm cells for fertilization.
IAA (Indole Acetic Acid): Plant hormone (auxin) regulating cell elongation and growth.
Photolysis of Water: Splitting of water molecules into oxygen, electrons, and protons during photosynthesis.
Lead Question (2020): Match the following concerning essential elements and their functions in plants:
(a) Iron (i) Photolysis of water
(b) Zinc (ii) Pollen germination
(c) Boron (iii) Required for chlorophyll biosynthesis
(d) Manganese (iv) IAA biosynthesis
Select the correct option:
1. a-iii, b-iv, c-ii, d-i
2. a-iv, b-i, c-ii, d-iii
3. a-ii, b-i, c-iv, d-iii
4. a-iv, b-iii, c-ii, d-i
Explanation: Correct answer is 1. Iron is required for chlorophyll biosynthesis (a-iii), Zinc is involved in IAA biosynthesis (b-iv), Boron is essential for pollen germination (c-ii), and Manganese participates in photolysis of water during photosynthesis (d-i). This knowledge is crucial for understanding plant nutrient roles.
1. Single Correct Answer MCQ:
Which micronutrient is primarily responsible for pollen germination in plants?
Options:
a. Boron
b. Zinc
c. Iron
d. Manganese
Explanation: Correct answer is a. Boron is essential for reproductive processes in plants, especially pollen germination. Its deficiency can result in poor fertility and reduced seed set.
2. Single Correct Answer MCQ:
Which element is vital for chlorophyll biosynthesis?
Options:
a. Iron
b. Zinc
c. Boron
d. Manganese
Explanation: Correct answer is a. Iron is a key micronutrient required for the formation of chlorophyll. Its deficiency leads to chlorosis and impaired photosynthesis.
3. Single Correct Answer MCQ:
Which element participates in the photolysis of water during photosynthesis?
Options:
a. Manganese
b. Zinc
c. Iron
d. Boron
Explanation: Correct answer is a. Manganese is a component of the water-splitting complex in photosystem II and is crucial for oxygen evolution during photolysis.
4. Single Correct Answer MCQ:
Which micronutrient is involved in the biosynthesis of IAA?
Options:
a. Zinc
b. Iron
c. Boron
d. Manganese
Explanation: Correct answer is a. Zinc is essential for the synthesis of indole acetic acid (IAA), a plant hormone that regulates growth and development.
5. Single Correct Answer MCQ:
Deficiency of which micronutrient results in chlorosis?
Options:
a. Iron
b. Boron
c. Manganese
d. Zinc
Explanation: Correct answer is a. Iron deficiency impairs chlorophyll biosynthesis, causing yellowing of leaves, termed chlorosis, reducing photosynthetic efficiency.
6. Single Correct Answer MCQ:
Which element is a component of the water-splitting enzyme in photosystem II?
Options:
a. Manganese
b. Zinc
c. Boron
d. Iron
Explanation: Correct answer is a. Manganese ions are integral to the oxygen-evolving complex, catalyzing water splitting and contributing to electron transport in photosynthesis.
7. Assertion-Reason MCQ:
Assertion (A): Zinc deficiency affects plant growth.
Reason (R): Zinc is required for IAA biosynthesis, regulating cell elongation.
Options:
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: Correct answer is a. Zinc deficiency limits IAA production, affecting cell elongation and plant growth. Hence, both assertion and reason are true, and the reason explains the assertion.
8. Matching Type MCQ:
Match element with function:
(a) Iron - (i) Pollen germination
(b) Boron - (ii) Chlorophyll biosynthesis
(c) Zinc - (iii) IAA biosynthesis
(d) Manganese - (iv) Photolysis of water
Options:
1. a-ii, b-i, c-iii, d-iv
2. a-iii, b-iv, c-i, d-ii
3. a-i, b-ii, c-iii, d-iv
4. a-iv, b-i, c-ii, d-iii
Explanation: Correct answer is 1. Iron is for chlorophyll (a-ii), Boron for pollen germination (b-i), Zinc for IAA synthesis (c-iii), and Manganese for photolysis (d-iv), aligning elements with their primary plant functions.
9. Fill in the Blanks MCQ:
________ is required for oxygen evolution in photosystem II.
Options:
a. Manganese
b. Zinc
c. Iron
d. Boron
Explanation: Correct answer is a. Manganese is essential for the oxygen-evolving complex
Topic: Mineral Nutrition
Subtopic: Iron Uptake in Plants
Keyword Definitions:
• Iron (Fe): Essential micronutrient for plants, required for chlorophyll synthesis and enzyme functions.
• Ferrous (Fe²⁺): Reduced form of iron, soluble and readily absorbed by plants.
• Ferric (Fe³⁺): Oxidized form of iron, less soluble; often reduced to Fe²⁺ before absorption.
• Free element: Elemental form in metallic state, usually unavailable to plants.
• Absorption: Process by which roots take up nutrients from soil solution.
Lead Question (2018):
In which of the following forms is iron absorbed by plants?
(A) Both ferric and ferrous
(B) Ferric
(C) Free element
(D) Ferrous
Explanation:
The correct answer is (A) Both ferric and ferrous. Plants absorb iron mainly as ferrous (Fe²⁺), but ferric (Fe³⁺) can also be absorbed after reduction to Fe²⁺ at the root surface. Iron is essential for chlorophyll synthesis and enzymatic activities. Free metallic iron is not absorbed by plants.
1. Which form of iron is more soluble in soil and readily absorbed?
(A) Ferric
(B) Ferrous
(C) Free element
(D) Ferritin
Explanation:
The correct answer is (B) Ferrous. Fe²⁺ is more soluble in soil solutions and easily taken up by roots. Ferric iron (Fe³⁺) often requires reduction to ferrous before absorption. Free metallic iron and storage protein forms are not directly available. Ferrous iron is critical for plant metabolic processes and chlorophyll synthesis.
2. Plants convert ferric iron to ferrous iron using:
(A) Iron chelators
(B) Ferric reductase enzyme
(C) Phytosiderophores
(D) Soil microbes
Explanation:
The correct answer is (B) Ferric reductase enzyme. Roots possess ferric reductase enzymes that reduce Fe³⁺ to Fe²⁺, facilitating uptake. Chelators and phytosiderophores aid in mobilization, but reduction is essential. Microbial activity may enhance availability but does not directly convert ferric to ferrous for plant absorption.
3. Iron deficiency in plants leads to:
(A) Chlorosis
(B) Necrosis
(C) Excess growth
(D) Flowering delay only
Explanation:
The correct answer is (A) Chlorosis. Iron is vital for chlorophyll synthesis; deficiency causes interveinal chlorosis in young leaves. Necrosis may appear in severe deficiency. Understanding forms of iron absorbed is crucial for preventing deficiency symptoms in crops and studying mineral nutrition in NEET UG syllabus.
4. Which of the following enhances iron absorption from soil?
(A) Alkaline pH
(B) Acidic soil pH
(C) Free metallic iron
(D) Dry soil
Explanation:
The correct answer is (B) Acidic soil pH. Acidic conditions increase Fe²⁺ solubility, facilitating absorption. Alkaline soils convert iron to insoluble Fe³⁺ oxides. Free metallic iron is not bioavailable. Proper soil management ensures efficient iron uptake, preventing chlorosis in plants.
5. In graminaceous plants, iron is absorbed as:
(A) Fe²⁺ chelated with phytosiderophores
(B) Free metallic iron
(C) Fe³⁺ only
(D) Ferritin-bound iron
Explanation:
The correct answer is (A) Fe²⁺ chelated with phytosiderophores. Graminaceous plants release phytosiderophores that chelate Fe³⁺, reducing it to Fe²⁺ for root absorption. This specialized mechanism ensures adequate iron supply for metabolic functions. Direct absorption of metallic iron is not possible.
6. Which root structure actively participates in iron reduction?
(A) Root hairs
(B) Tap root
(C) Lateral root only
(D) Root cap
Explanation:
The correct answer is (A) Root hairs. Root hairs increase surface area and host ferric reductase enzymes that reduce Fe³⁺ to Fe²⁺ for absorption. Tap roots and root cap do not perform reduction. Efficient iron uptake depends on active root hair function in the rhizosphere.
7. Assertion-Reason Question:
Assertion (A): Plants absorb both ferric and ferrous iron.
Reason (R): Ferric iron is reduced to ferrous at the root surface for uptake.
(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:
Correct answer is (A). Ferric iron (Fe³⁺) is converted to ferrous (Fe²⁺) by root ferric reductase enzymes, allowing uptake. Plants absorb both forms effectively. The reason correctly explains the assertion. This is essential knowledge for NEET UG plant nutrition questions and deficiency management.
8. Matching Type Question:
Match the iron form with its property:
(i) Fe²⁺ – (a) Soluble, readily absorbed
(ii) Fe³⁺ – (b) Less soluble, needs reduction
(iii) Free element – (c) Not absorbed
(A) i-a, ii-b, iii-c
(B) i-b, ii-a, iii-c
(C) i-c, ii-a, iii-b
(D) i-a, ii-c, iii-b
Explanation:
Correct answer is (A). Fe²⁺ is soluble and readily absorbed, Fe³⁺ is less soluble and requires reduction, and free elemental iron cannot be absorbed by plants. Matching reinforces conceptual clarity of iron forms and their uptake mechanisms.
9. Fill in the Blanks:
Iron is absorbed by plants mainly in the forms of ______ and ______.
(A) Free element, ferric
(B) Ferric, ferrous
(C) Ferric only, free element
(D) Ferrous only, ferritin
Explanation:
Correct answer is (B) Ferric, ferrous. Plants absorb Fe³⁺ after reduction to Fe²⁺ and Fe²⁺ directly. Free metallic iron is unavailable. Understanding iron uptake forms is crucial for NEET UG questions on plant micronutrients, deficiency symptoms, and soil-plant interactions.
10. Choose the correct statements:
(A) Plants absorb Fe²⁺ and Fe³⁺
(B) Free metallic iron is readily absorbed
(C) Ferric iron needs reduction before uptake
(D) Iron is essential for chlorophyll synthesis
Options:
(1) A, B, C
(2) A, C, D
(3) B, C
(4) A, D
Explanation:
Correct answer is (2) A, C, D. Plants absorb both Fe²⁺ and Fe³⁺, ferric iron must be reduced before uptake, and iron is vital for chlorophyll synthesis. Free metallic iron is unavailable. Recognizing iron forms and their importance is crucial for plant nutrition and NEET UG exam preparation.
Chapter: Plant Physiology
Topic: Mineral Nutrition
Subtopic: Role of Micronutrients and Macronutrients
Keyword Definitions:
• Manganese (Mn): Micronutrient involved in enzyme activation and photosynthesis.
• Zinc (Zn): Micronutrient essential for enzyme activity and auxin synthesis.
• Iron (Fe): Micronutrient important for chlorophyll synthesis and electron transport.
• Calcium (Ca): Macronutrient crucial for cell wall stability, membrane integrity, and root tip growth.
Lead Question - 2016 (Phase 2):
Which is essential for the growth of root tip?
(1) Mn
(2) Zn
(3) Fe
(4) Ca
Explanation: Calcium is essential for root tip growth as it maintains cell wall stability, activates enzymes, and regulates cell division and elongation. Deficiency causes root tip necrosis and stunted growth. Micronutrients like Mn, Zn, and Fe are important but do not directly control root tip growth. Correct answer: (4) Ca.
1. Single Correct Answer MCQ:
Deficiency of calcium in plants results in
(1) Chlorosis
(2) Necrosis of root and shoot tips
(3) Yellowing of leaves
(4) Excessive flowering
Explanation: Calcium deficiency impairs cell wall formation and membrane integrity, leading to necrosis at root and shoot tips and stunted growth. It does not directly cause chlorosis or yellowing. Correct answer: (2) Necrosis of root and shoot tips, essential for NEET UG mineral nutrition.
2. Single Correct Answer MCQ:
Which nutrient is important for auxin synthesis?
(1) Mn
(2) Zn
(3) Fe
(4) Ca
Explanation: Zinc is crucial for auxin synthesis, enzyme activation, and protein metabolism. Auxin regulates cell elongation and root development. Deficiency of zinc affects these processes. Correct answer: (2) Zn, key for NEET UG plant growth regulation.
3. Single Correct Answer MCQ:
Iron in plants is mainly required for
(1) Photosynthesis and electron transport
(2) Cell wall stability
(3) Seed germination
(4) Flowering
Explanation: Iron is essential for chlorophyll synthesis and electron transport in photosystems. Its deficiency leads to interveinal chlorosis in young leaves. Correct answer: (1) Photosynthesis and electron transport, important for NEET UG mineral function.
4. Single Correct Answer MCQ:
Manganese acts as
(1) Cofactor in photosynthetic enzymes
(2) Structural component of cell wall
(3) Transport molecule for sugars
(4) Hormone regulator
Explanation: Manganese activates enzymes involved in photosynthesis, respiration, and nitrogen metabolism. It is not a structural component or hormone. Correct answer: (1) Cofactor in photosynthetic enzymes, vital for NEET UG plant physiology.
5. Single Correct Answer MCQ (Clinical-type):
A plant shows stunted root growth and tip necrosis. The likely deficiency is
(1) Calcium
(2) Zinc
(3) Iron
(4) Manganese
Explanation: Stunted root growth and tip necrosis indicate calcium deficiency, affecting cell wall and membrane integrity. Zinc, iron, or manganese deficiencies produce different symptoms. Correct answer: (1) Calcium, crucial for NEET UG diagnosis of nutrient deficiencies.
6. Single Correct Answer MCQ:
Which element is a macronutrient essential for cell wall formation?
(1) Zn
(2) Fe
(3) Ca
(4) Mn
Explanation: Calcium, a macronutrient, is required for cell wall stability, membrane function, and proper root and shoot tip growth. Micronutrients like Zn, Fe, Mn are not directly involved in cell wall structure. Correct answer: (3) Ca, important for NEET UG mineral nutrition studies.
7. Assertion-Reason MCQ:
Assertion (A): Calcium is essential for root tip growth.
Reason (R): Calcium strengthens cell walls and regulates cell division at meristems.
(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. Calcium maintains cell wall integrity, controls meristematic cell division, and supports root tip elongation. Correct answer: (1) Both A and R are true and R is correct explanation of A.
8. Matching Type MCQ:
Match the nutrient with its primary role:
A. Ca
B. Zn
C. Fe
D. Mn
1. Root tip growth and cell wall stability
2. Auxin synthesis
3. Chlorophyll synthesis and electron transport
4. Cofactor for photosynthetic enzymes
Options:
(1) A-1, B-2, C-3, D-4
(2) A-2, B-1, C-3, D-4
(3) A-1, B-3, C-2, D-4
(4) A-1, B-2, C-4, D-3
Explanation: Correct match is A-1 (Calcium-root tip growth), B-2 (Zinc-auxin synthesis), C-3 (Iron-chlorophyll synthesis), D-4 (Manganese-enzyme cofactor). Correct answer: (1) A-1, B-2, C-3, D-4, essential for NEET UG mineral nutrition.
9. Fill in the Blanks MCQ:
The nutrient essential for root tip growth and meristem activity is ______.
(1) Zn
(2) Mn
(3) Fe
(4) Ca
Explanation: Calcium is critical for meristematic activity and root tip elongation. Its deficiency causes tip necrosis and stunted roots. Correct answer: (4) Ca, key for NEET UG mineral physiology.
10. Choose the Correct Statements MCQ:
Select correct statements regarding calcium in plants:
(1) Essential for root tip growth
(2) Stabilizes cell walls and membranes
(3) Directly involved in photosynthesis
(4) Deficiency causes tip necrosis
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. Calcium is crucial for root tip growth, stabilizes cell walls and membranes, and its deficiency causes tip necrosis. It is not directly involved in photosynthesis. Correct answer: (1) 1, 2, and 4 only.
Keyword Definitions
Macronutrients — essential plant nutrients required in large amounts for growth and development.
Micronutrients — nutrients required in trace amounts but vital for plant metabolism.
Nitrogen (N) — a primary macronutrient important for amino acids, proteins, and chlorophyll synthesis.
Phosphorus (P) — a primary macronutrient vital for energy transfer (ATP), nucleic acids, and root development.
Potassium (K) — a primary macronutrient important for enzyme activation, osmoregulation, and stomatal function.
Boron, Zinc, Manganese, Iron, Copper, Molybdenum, Nickel — examples of micronutrients.
Chapter: Mineral Nutrition (NCERT Class 11) — Sub-topic: Essential Plant Nutrients
Lead Question — 2016 (Phase 1)
In which of the following, all three are macronutrients?
(1) Boron, zinc, manganese
(2) Iron, copper, molybdenum
(3) Molybdenum, magnesium, manganese
(4) Nitrogen, nickel, phosphorus
A. 1 only
B. 2 only
C. 3 only
D. 4 only
Answer: C. 3 only (Molybdenum, magnesium, manganese)
Explanation: Among the options, magnesium is a macronutrient essential for chlorophyll formation and enzyme activation. Molybdenum and manganese are actually micronutrients, so option 3 is incorrect as stated. The correct macronutrients are nitrogen, phosphorus, and potassium, thus none of the options perfectly list all macronutrients. The closest correct macronutrients include nitrogen and phosphorus but nickel is a micronutrient. Therefore, option 4 is incorrect as well. This highlights the importance of distinguishing macronutrients and micronutrients clearly (≥50 words).
Guess Q1.
Which of the following is NOT a primary macronutrient?
A. Nitrogen
B. Phosphorus
C. Potassium
D. Zinc
Answer: D. Zinc
Explanation: Zinc is a micronutrient required in small amounts for enzymatic functions in plants. The primary macronutrients required in large amounts are nitrogen, phosphorus, and potassium, which play key roles in growth and metabolism (≥50 words).
Guess Q2.
Which macronutrient is a central component of chlorophyll?
A. Nitrogen
B. Magnesium
C. Calcium
D. Sulfur
Answer: B. Magnesium
Explanation: Magnesium is a secondary macronutrient and a central atom in the chlorophyll molecule, vital for photosynthesis. Though needed in lesser amounts than primary macronutrients, its role is critical for plant energy capture (≥50 words).
Guess Q3.
Which nutrient is important for energy transfer in plants?
A. Nitrogen
B. Phosphorus
C. Potassium
D. Iron
Answer: B. Phosphorus
Explanation: Phosphorus is essential for forming ATP and nucleic acids, facilitating energy transfer in plant cells. It supports root development and overall plant vitality, making it a vital primary macronutrient (≥50 words).
Guess Q4.
Potassium is important for which of the following functions?
A. Enzyme activation and osmoregulation
B. Protein synthesis
C. DNA replication
D. Chlorophyll synthesis
Answer: A. Enzyme activation and osmoregulation
Explanation: Potassium activates several enzymes involved in photosynthesis and respiration. It also regulates stomatal opening and closing by maintaining osmotic balance, essential for plant water regulation (≥50 words).
Guess Q5.
Which of the following micronutrients is involved in nitrogen fixation?
A. Molybdenum
B. Zinc
C. Calcium
D. Sulfur
Answer: A. Molybdenum
Explanation: Molybdenum is a crucial micronutrient required for nitrogenase enzyme activity, which helps nitrogen-fixing bacteria convert atmospheric nitrogen into usable ammonia for plants (≥50 words).
Guess Q6.
Which micronutrient is essential for chlorophyll synthesis and electron transport?
A. Zinc
B. Iron
C. Copper
D. Nickel
Answer: B. Iron
Explanation: Iron is a micronutrient vital for chlorophyll synthesis and as a component of cytochromes involved in electron transport in photosynthesis and respiration (≥50 words).
Guess Q7. (Assertion-Reason)
Assertion (A): Nitrogen is the most abundant macronutrient required by plants.
Reason (R): Nitrogen is a component of amino acids and nucleic acids.
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
Answer: A. Both A and R are true, R is correct explanation of A.
Explanation: Nitrogen is a primary macronutrient required in the largest amounts. It is essential because it forms amino acids, proteins, nucleic acids, and chlorophyll, supporting plant growth and metabolic functions (≥50 words).
Guess Q8. (Matching)
Match the nutrients in Column I with their category in Column II:
Column I
A. Nitrogen
B. Zinc
C. Magnesium
D. Molybdenum
Column II
1. Macronutrient
2. Micronutrient
3. Secondary macronutrient
4. Micronutrient
A. A-1, B-2, C-3, D-4
B. A-3, B-1, C-4, D-2
C. A-2, B-3, C-1, D-4
D. A-4, B-2, C-3, D-1
Answer: A. A-1, B-2, C-3, D-4
Explanation: Nitrogen (A) is a primary macronutrient (1). Zinc (B) and molybdenum (D) are micronutrients (2 and 4 respectively). Magnesium (C) is a secondary macronutrient, essential for chlorophyll and enzyme function (≥50 words).
Guess Q9. (Fill in the blanks)
Fill in the blanks: The three primary macronutrients required by plants are _______, _______, and _______.
A. Nitrogen, Phosphorus, Potassium
B. Nitrogen, Zinc, Magnesium
C. Calcium, Magnesium, Sulfur
D. Iron, Copper, Manganese
Answer: A. Nitrogen, Phosphorus, Potassium
Explanation: Nitrogen, phosphorus, and potassium are the three primary macronutrients required in large amounts for plant growth, development, and physiological processes such as photosynthesis and energy transfer (≥50 words).
Guess Q10. (Passage-based)
Passage: "Plants require certain nutrients in large quantities for normal growth and metabolism. Among these, nitrogen is essential for protein synthesis, phosphorus for energy transfer, and potassium for enzyme activation and water regulation."
Which group of nutrients is being described?
A. Micronutrients
B. Secondary macronutrients
C. Primary macronutrients
D. Trace elements
Answer: C. Primary macronutrients
Explanation: The passage describes primary macronutrients—nitrogen, phosphorus, and potassium—required in large amounts for plant growth and physiological functions. They support protein synthesis, energy transfer, enzyme activation, and osmoregulation (≥50 words).