Topic: Differentiation and Growth Processes; Subtopic: Cellular Differentiation, Dedifferentiation and Redifferentiation
Keyword Definitions:
Differentiation: The process by which cells become specialized in structure and function during plant growth.
Dedifferentiation: The process in which mature differentiated cells regain the capacity to divide and form meristematic tissues.
Redifferentiation: The process by which dedifferentiated cells again become specialized to perform specific functions.
Meristematic Tissue: A group of actively dividing cells responsible for plant growth.
Lead Question – 2024
Formation of interfascicular cambium from fully developed parenchyma cells is an example for:
(1) Redifferentiation
(2) Dedifferentiation
(3) Maturation
(4) Differentiation
Explanation: Formation of interfascicular cambium from mature parenchyma cells is an example of dedifferentiation. In this process, mature cells revert to a meristematic state to regain the ability to divide. These newly formed meristematic cells later form vascular tissues during secondary growth. Hence, the correct answer is option (2).
Guessed Question 1: Cells that lose the ability to divide permanently are said to have undergone:
(1) Redifferentiation
(2) Dedifferentiation
(3) Differentiation
(4) Maturation
Explanation: Differentiation is the process by which cells lose the ability to divide and become specialized for particular functions. Once a cell differentiates, it performs specific roles such as xylem or phloem function. Hence, the correct option is (3).
Guessed Question 2: Dedifferentiation helps in the formation of which of the following tissues during secondary growth?
(1) Cork cambium and vascular cambium
(2) Phloem and xylem
(3) Epidermis and pericycle
(4) Collenchyma and sclerenchyma
Explanation: During secondary growth, permanent tissues like parenchyma cells regain meristematic activity through dedifferentiation and form cork cambium (phellogen) and vascular cambium, which help in producing new cells. Thus, the correct option is (1).
Guessed Question 3: Redifferentiation results in the formation of:
(1) New meristematic cells
(2) Permanent tissues with specific functions
(3) Immature undifferentiated cells
(4) Dead cells only
Explanation: Redifferentiation is the process where dedifferentiated meristematic cells again specialize into permanent cells performing definite functions, like xylem or phloem formation. Therefore, the correct answer is option (2).
Guessed Question 4: Which of the following statements correctly differentiates differentiation from dedifferentiation?
(1) Differentiation forms permanent cells; dedifferentiation forms meristematic cells
(2) Both lead to permanent tissue formation
(3) Both involve loss of cell division
(4) Dedifferentiation forms dead tissues
Explanation: Differentiation leads to the formation of permanent cells from meristematic ones, while dedifferentiation reverses this process, converting permanent cells back into meristematic ones. Hence, option (1) correctly explains their difference.
Guessed Question 5: Which of the following is an example of dedifferentiation in plants?
(1) Formation of cork cambium from cortex cells
(2) Formation of root hairs
(3) Conversion of parenchyma to collenchyma
(4) Differentiation of xylem vessels
Explanation: Dedifferentiation occurs when parenchyma or other permanent cells regain the ability to divide, such as during the formation of cork cambium (phellogen) from cortical cells. Hence, the correct option is (1).
Guessed Question 6: During secondary growth, the vascular cambium formed between xylem and phloem is derived from:
(1) Xylem only
(2) Phloem only
(3) Intrafascicular and interfascicular regions
(4) Cortex only
Explanation: The vascular cambium arises from both intrafascicular cambium (within vascular bundles) and interfascicular cambium (between vascular bundles). The latter originates from dedifferentiated parenchyma cells. Hence, option (3) is correct.
Guessed Question 7: Assertion–Reason Type
Assertion (A): Dedifferentiation occurs in mature plant cells.
Reason (R): It enables mature cells to regain the capacity to divide.
(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
(3) A is true but R is false
(4) A is false but R is true
Explanation: Dedifferentiation indeed occurs in mature cells and allows them to divide again, forming meristematic tissues like cambium. Hence, both statements are true, and R correctly explains A. Correct option is (1).
Guessed Question 8: Matching Type
Match the following terms with their correct descriptions:
A. Dedifferentiation — I. Loss of specialization
B. Differentiation — II. Development of permanent cells
C. Redifferentiation — III. Formation of new specialized cells
D. Meristem — IV. Region of actively dividing cells
Choose the correct match:
(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-I, C-II, D-III
Explanation: Dedifferentiation (A-I) refers to loss of specialization; differentiation (B-II) forms permanent cells; redifferentiation (C-III) again creates specialized cells, and meristem (D-IV) represents actively dividing cells. Hence, option (1) is correct.
Guessed Question 9: Fill in the Blank
The process by which parenchyma cells regain the power of division to form cambium is called __________.
(1) Differentiation
(2) Dedifferentiation
(3) Redifferentiation
(4) Maturation
Explanation: When parenchyma cells regain meristematic activity to form cambium during secondary growth, it is called dedifferentiation. This allows further formation of vascular tissues, contributing to plant growth. Therefore, the correct option is (2).
Guessed Question 10: Choose the Correct Statements
Statement I: Redifferentiation leads to formation of specialized cells.
Statement II: Dedifferentiation forms permanent tissues from meristematic cells.
(1) Both statements are true
(2) Both statements are false
(3) Statement I true, II false
(4) Statement I false, II true
Explanation: Redifferentiation indeed leads to specialized cell formation, while dedifferentiation converts permanent cells into meristematic ones. Thus, Statement I is true and II is false. Correct option is (3).
Topic: Phases of Plant Growth; Subtopic: Meristematic and Elongation Phases
Keyword Definitions:
Meristem: Region of actively dividing cells in plants responsible for growth.
Vacuolation: Formation or enlargement of vacuoles in plant cells, contributing to cell elongation.
Determinate Growth: Growth that ceases after reaching a specific size, as in leaves and flowers.
Indeterminate Growth: Continuous growth without a fixed limit, as in roots and shoots.
Plasmodesmata: Cytoplasmic channels connecting plant cells, allowing intercellular communication.
Cell Elongation: Phase in plant growth where cells increase in size, largely due to water uptake and vacuole expansion.
Measurable Growth: Quantifiable increase in plant size, length, or mass over time.
Lead Question – 2023 (Manipur)
Which of the following statements is not correct?
1. Phase of cell elongation of plant cells is characterized by increased vacuolation.
2. Cells in the meristematic phase of growth exhibit abundant plasmodesmatal connections
3. Plant growth is generally determinate
4. Plant growth is measurable
Explanation: Plant growth occurs in meristematic and elongation phases. Meristematic cells divide actively and have abundant plasmodesmatal connections. In elongation, cells increase in size due to vacuolation. Plant growth is generally indeterminate, especially in shoots and roots, allowing continuous development. Growth is measurable in length, volume, or biomass. Statement 3 is incorrect because not all plant growth is determinate; many organs like stems and roots show indeterminate growth. Correct answer: 3. Plant growth is generally determinate.
1. Single Correct Answer MCQ:
Which plant tissue is responsible for primary growth?
1. Lateral meristem
2. Apical meristem
3. Cork cambium
4. Vascular cambium
Explanation: Apical meristems at root and shoot tips are responsible for primary growth, producing new cells that increase plant length. Lateral meristems contribute to secondary growth, thickening stems and roots. Correct answer: 2. Apical meristem.
2. Single Correct Answer MCQ:
During which phase do plant cells enlarge predominantly due to vacuole expansion?
1. Meristematic phase
2. Elongation phase
3. Maturation phase
4. Differentiation phase
Explanation: In the elongation phase, plant cells increase in size primarily by water uptake into the central vacuole, stretching the cell wall and contributing to organ length. Correct answer: 2. Elongation phase.
3. Single Correct Answer MCQ:
Plasmodesmata are most abundant in:
1. Mature cells
2. Elongating cells
3. Meristematic cells
4. Dead cells
Explanation: Meristematic cells require extensive intercellular communication for coordinated division and differentiation. Plasmodesmata are cytoplasmic channels that facilitate this. Correct answer: 3. Meristematic cells.
4. Single Correct Answer MCQ:
Which type of plant growth is unlimited and continues throughout life?
1. Determinate growth
2. Indeterminate growth
3. Primary growth
4. Secondary growth
Explanation: Indeterminate growth allows continuous elongation of roots and shoots without a predetermined limit, unlike determinate growth seen in leaves and flowers. Correct answer: 2. Indeterminate growth.
5. Single Correct Answer MCQ:
Cell elongation in plants is mainly due to:
1. DNA replication
2. Vacuole enlargement
3. Plasmodesmatal reduction
4. Chromosome separation
Explanation: Vacuole expansion absorbs water, stretching the cell wall and increasing cell length during elongation. This is the main mechanism behind rapid plant growth in elongation zones. Correct answer: 2. Vacuole enlargement.
6. Single Correct Answer MCQ:
Which meristem is responsible for secondary growth in plants?
1. Apical meristem
2. Intercalary meristem
3. Lateral meristem
4. Root cap meristem
Explanation: Lateral meristems, including vascular cambium and cork cambium, increase girth in stems and roots, producing secondary xylem and phloem. Correct answer: 3. Lateral meristem.
7. Assertion-Reason MCQ:
Assertion (A): Cells in the elongation phase have enlarged vacuoles.
Reason (R): Vacuole expansion generates turgor pressure, driving cell elongation.
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 elongation phase depends on vacuole expansion, which creates turgor pressure stretching cell walls. This mechanism enables rapid plant growth. Correct answer: 1.
8. Matching Type MCQ:
Match plant growth phases with characteristics:
A. Meristematic – (i) Cell division
B. Elongation – (ii) Vacuole expansion
C. Maturation – (iii) Differentiation
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: Meristematic cells divide actively, elongation involves vacuole expansion, and maturation entails differentiation into specialized cell types. Correct answer: 1.
9. Fill in the Blanks MCQ:
Growth that stops after reaching a specific size is called ______.
1. Indeterminate growth
2. Determinate growth
3. Primary growth
4. Secondary growth
Explanation: Determinate growth occurs in organs like leaves and flowers, ceasing once the structure reaches its mature size, unlike indeterminate growth which continues indefinitely. Correct answer: 2.
10. Choose the Correct Statements MCQ:
Statement I: Meristematic cells are small with dense cytoplasm.
Statement II: Elongating cells have large vacuoles for cell expansion.
1. Both true
2. Both false
3. I true, II false
4. I false, II true
Explanation: Meristematic cells are actively dividing with dense cytoplasm and small vacuoles. Elongating cells expand due to vacuole enlargement, increasing cell length and contributing to organ growth. Correct answer: 1.
Keyword Definitions:
Flower: A reproductive shoot of angiosperms where the shoot apical meristem converts into a floral meristem to produce floral organs.
Shoot apical meristem: The growing tip of the shoot responsible for primary growth and formation of leaves, branches, or flowers.
Floral meristem: Specialized meristem that produces floral organs such as sepals, petals, stamens, and carpels.
Internode: The segment of the stem between two successive nodes.
Floral appendages: The lateral organs of a flower including sepals, petals, stamens, and carpels.
Node: Point on the stem where leaves, branches, or floral appendages arise.
Modified shoot: A shoot adapted to perform a function different from regular vegetative growth.
Floral morphogenesis: The developmental process that determines the formation and arrangement of floral organs.
Angiosperm: Flowering plant that produces seeds enclosed within a fruit.
Vegetative growth: Growth phase producing stems, leaves, and roots.
Reproductive shoot: Shoot specialized for sexual reproduction, giving rise to flowers and fruits.
Lead Question - 2023:
Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R:
Assertion A: A flower is defined as modified shoot wherein the shoot apical meristem changes to floral meristem.
Reason R: Internode of the shoot gets condensed to produce different floral appendages laterally at successive nodes instead of leaves.
Choose the correct answer from the options given below:
(1) A is true but R is false
(2) A is false but R is true
(3) Both A and R are true and R is the correct explanation of A
(4) Both A and R are true but R is not the correct explanation of A
Answer & Explanation: (3) Both A and R are true and R is the correct explanation of A. A flower is indeed a modified shoot in which the shoot apical meristem transitions to a floral meristem, initiating reproductive development. The internodes condense, and floral appendages—sepals, petals, stamens, and carpels—develop laterally at successive nodes, replacing leaves. This morphological modification is fundamental to angiosperm reproduction, ensuring compact arrangement of reproductive organs. Understanding this mechanism explains floral architecture, organ differentiation, and evolution of reproductive strategies. Both statements are correct, and the condensation of internodes directly explains the modification of shoot into flower.
1. Which meristem is responsible for producing floral organs?
(1) Shoot apical meristem
(2) Root apical meristem
(3) Floral meristem
(4) Intercalary meristem
Explanation: Floral meristem is specialized to produce sepals, petals, stamens, and carpels in a flower. Correct answer is (3).
2. A condensed internode in a flower contributes to:
(1) Leaf formation
(2) Lateral floral appendages
(3) Root growth
(4) Stem elongation
Explanation: Condensed internodes in a flower ensure compact arrangement of floral appendages laterally at nodes, replacing leaves. Correct answer is (2).
3. Sepals, petals, stamens, and carpels arise from:
(1) Nodes
(2) Axillary buds
(3) Floral meristem
(4) Root cap
Explanation: The floral meristem produces all floral organs including sepals, petals, stamens, and carpels. Correct answer is (3).
4. A flower is essentially a modified:
(1) Leaf
(2) Root
(3) Shoot
(4) Internode
Explanation: Morphologically, a flower is a modified shoot where apical meristem transitions to floral meristem for reproductive organ development. Correct answer is (3).
5. Node in a flower refers to:
(1) Point of leaf attachment
(2) Point of floral appendage development
(3) Root-shoot junction
(4) Stem apex
Explanation: In flowers, nodes are points on the condensed shoot where floral appendages such as sepals, petals, stamens, and carpels arise. Correct answer is (2).
6. Internode condensation in flowers helps in:
(1) Elongating stem
(2) Compact arrangement of reproductive organs
(3) Leaf expansion
(4) Root elongation
Explanation: Condensed internodes bring floral organs close together, forming a compact and organized flower, essential for effective reproduction. Correct answer is (2).
Assertion-Reason Question
7. Assertion (A): Floral meristem arises from shoot apical meristem.
Reason (R): Vegetative apical meristem can differentiate into reproductive meristem under hormonal control.
(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: Floral meristem develops from shoot apical meristem when vegetative meristem transitions to reproductive phase, regulated by hormones. Correct answer is (1).
Matching Type Question
8. Match List I with List II:
A. Sepal – i. Protects flower in bud stage
B. Petal – ii. Attracts pollinators
C. Stamen – iii. Male reproductive organ
D. Carpel – iv. Female reproductive organ
(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: Sepal protects flower; petal attracts pollinators; stamen is male organ; carpel is female organ. Correct answer is (1).
Fill in the Blanks Question
9. The point of attachment of floral appendages on the condensed shoot is called ________.
(1) Node
(2) Internode
(3) Apex
(4) Peduncle
Explanation: Floral appendages arise laterally from nodes of condensed floral shoot. Correct answer is (1).
Choose the Correct Statements Question
10. Statement I: Flower is a modified shoot.
Statement II: Leaf is modified into floral organ in all plants.
(1) Only Statement I is correct
(2) Only Statement II is correct
(3) Both I and II are correct
(4) Both I and II are incorrect
Explanation: A flower is a modified shoot (Statement I correct). Not all leaves modify into floral organs; leaves mostly remain vegetative. Correct answer is (1).
Topic: Plant Development and Adaptation; Subtopic: Plasticity and Differentiation
Keyword Definitions:
• Redifferentiation: Process by which already differentiated cells regain the ability to divide and form new structures.
• Development: Series of progressive changes in plant structure and function from germination to maturity.
• Plasticity: Ability of plants to alter growth or development in response to environmental conditions.
• Differentiation: Process by which cells acquire specialized structure and function.
• Environmental stimuli: External factors like light, temperature, water, and nutrients affecting plant growth.
• Meristem: Region of actively dividing undifferentiated cells in plants.
• Structural adaptation: Formation of specialized organs or tissues in response to environment.
• Phenotypic variation: Observable differences in plant morphology due to environmental influence.
• Plastic response: Non-genetic modification of plant development under environmental conditions.
• Auxins: Plant hormones regulating growth and differentiation.
• Adaptive growth: Morphological changes enhancing survival under specific conditions.
Lead Question - 2022 (Ganganagar)
The ability of plants to follow different pathways in response to environment leading to formation of different kinds of structures is called:
1. Redifferentiation
2. Development
3. Plasticity
4. Differentiation
Explanation: Plasticity is the capacity of plants to modify their development and morphology in response to environmental cues, producing different structures without altering genetic information. Redifferentiation refers to cells regaining division ability, differentiation is cell specialization, and development is overall growth progression. Plasticity allows adaptive growth for survival, such as forming adventitious roots under waterlogging or thicker leaves under drought. It demonstrates plants’ remarkable flexibility in responding to stimuli. Correct answer is 3. Plasticity. This ability ensures ecological success by enabling plants to optimize resource acquisition and maintain physiological functions under diverse environmental conditions.
1. Single Correct Answer MCQ:
Which plant process involves cells acquiring specialized functions?
a) Plasticity
b) Differentiation
c) Redifferentiation
d) Development
Explanation: Differentiation is the process where cells become specialized in structure and function. Plasticity involves environmental response, redifferentiation is re-entry into division, and development is overall growth. Correct answer is b) Differentiation.
2. Single Correct Answer MCQ:
Adventitious root formation under waterlogged conditions exemplifies:
a) Development
b) Differentiation
c) Plasticity
d) Redifferentiation
Explanation: The formation of adventitious roots due to environmental stress illustrates plasticity, as the plant modifies development for survival. Correct answer is c) Plasticity.
3. Single Correct Answer MCQ:
Cells regaining the ability to divide and form new structures undergo:
a) Redifferentiation
b) Differentiation
c) Plasticity
d) Development
Explanation: Redifferentiation allows previously specialized cells to divide again and produce new structures, often seen in tissue culture or injury response. Correct answer is a) Redifferentiation.
4. Single Correct Answer MCQ:
Overall growth and progression from germination to maturity is termed:
a) Plasticity
b) Development
c) Differentiation
d) Redifferentiation
Explanation: Development encompasses the entire sequence of growth and functional changes in a plant from seed to mature form. Correct answer is b) Development.
5. Single Correct Answer MCQ:
Modification of leaf thickness in response to drought is an example of:
a) Plasticity
b) Redifferentiation
c) Differentiation
d) Development
Explanation: Leaf morphological changes under drought represent plasticity, demonstrating the plant’s ability to adapt developmentally to environmental stress. Correct answer is a) Plasticity.
6. Single Correct Answer MCQ:
Which hormone regulates cell differentiation in plants?
a) Auxin
b) Gibberellin
c) Cytokinin
d) Ethylene
Explanation: Auxins play a central role in regulating cell elongation and differentiation, affecting organ formation and tissue specialization. Correct answer is a) Auxin.
7. Assertion-Reason MCQ:
Assertion (A): Plasticity allows plants to survive diverse environmental conditions.
Reason (R): Plasticity leads to different structural adaptations without genetic changes.
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: Plasticity results in adaptive structural and functional modifications, enhancing survival in varied environments without changing genetic makeup. Both assertion and reason are true, and the reason explains the assertion. Correct answer is a) Both A and R are true, R explains A.
8. Matching Type MCQ:
Match the term with its description:
Column I
A) Plasticity
B) Differentiation
C) Redifferentiation
D) Development
Column II
1) Cells regain division capacity
2) Overall growth and maturation
3) Environmental response modifications
4) Cells acquire specialized functions
Choices:
A-__ B-__ C-__ D-__
Explanation: Correct matches are: Plasticity (A-3), Differentiation (B-4), Redifferentiation (C-1), Development (D-2). Plasticity allows adaptive growth, differentiation specializes cells, redifferentiation restores division, development covers overall progression.
9. Fill in the Blanks / Completion MCQ:
The ability of plants to alter growth or morphology due to environment is called __________.
a) Redifferentiation
b) Differentiation
c) Plasticity
d) Development
Explanation: Plasticity enables plants to modify growth and structure in response to environmental factors without changing their genetic makeup. Correct answer is c) Plasticity.
10. Choose the correct statements MCQ (Statement I & II):
Statement I: Plasticity leads to formation of different structures under varied conditions.
Statement II: Plasticity involves genetic modification in plants.
a) Both I and II are correct
b) Only I is correct
c) Only II is correct
d) Both are incorrect
Explanation: Plasticity allows structural and functional changes in response to the environment without altering genes. Statement I is correct; Statement II is false. Correct answer is b) Only I is correct.
Subtopic: Axillary Buds and Meristems
Axillary buds: Buds formed in the axil of a leaf that can develop into branches or flowers.
Meristem: Tissue in plants consisting of undifferentiated cells capable of division and growth.
Apical meristem: Meristem located at the tips of roots and shoots, responsible for primary growth.
Lateral meristem: Meristem responsible for secondary growth, increasing girth of stems and roots.
Intercalary meristem: Meristem present at the base of nodes or internodes, promoting elongation.
Secondary meristem: Same as lateral meristem, involved in thickening of stems and roots.
Primary growth: Growth resulting from apical meristem activity, increasing length of plant organs.
Secondary growth: Growth due to lateral meristem, increasing thickness or girth of stems and roots.
Leaf axil: The angle formed between a leaf and the stem where axillary buds are located.
Branching: Development of lateral shoots from axillary buds for plant architecture.
Vegetative propagation: Growth from plant parts like buds, roots, or stems to form new plants.
Lead Question - 2022 (Abroad)
Axillary buds are derived from the activity of:
Lateral meristem
Secondary meristem
Apical meristem
Intercalary meristem
Explanation: Axillary buds originate from the apical meristem, specifically as a result of leaf axil development. These buds can give rise to branches or flowers. Lateral, intercalary, and secondary meristems are involved in stem thickening or elongation, not direct axillary bud formation. Answer: Apical meristem. Answer: 3
Q1: Which meristem is responsible for elongation of internodes in grasses?
Apical meristem
Intercalary meristem
Lateral meristem
Secondary meristem
Explanation: Intercalary meristem is present at the base of nodes or internodes in grasses and facilitates rapid elongation. Apical meristems promote overall shoot/root growth, lateral/secondary meristems increase girth. Answer: Intercalary meristem. Answer: 2
Q2: Lateral meristems contribute to:
Primary growth
Secondary growth
Leaf formation
Flowering
Explanation: Lateral meristems, including vascular cambium and cork cambium, are responsible for secondary growth, increasing stem and root thickness. They do not contribute directly to primary elongation, leaf, or flower formation. Answer: Secondary growth. Answer: 2
Q3: Buds developing at the shoot tip are known as:
Axillary buds
Apical buds
Accessory buds
Adventitious buds
Explanation: Apical buds are located at the shoot tip and are responsible for primary growth and elongation. Axillary buds are in leaf axils, adventitious buds develop from non-standard locations. Answer: Apical buds. Answer: 2
Q4: Which meristem type is involved in girth increase of dicot stems?
Apical meristem
Lateral meristem
Intercalary meristem
Terminal meristem
Explanation: Lateral meristem, particularly vascular cambium, facilitates secondary growth, increasing the thickness of dicot stems. Apical meristem increases length, intercalary meristem elongates internodes, terminal meristem is another name for apical. Answer: Lateral meristem. Answer: 2
Q5: Axillary buds can develop into:
Roots
Leaves
Branches or flowers
Cambium
Explanation: Axillary buds, present in the leaf axil, have the potential to grow into lateral branches or flowers. Roots and cambium do not originate from axillary buds. Answer: Branches or flowers. Answer: 3
Q6: Intercalary meristems are commonly found in:
Dicot stems
Monocot stems such as grasses
Roots
Leaf margins
Explanation: Intercalary meristems occur at the base of nodes or internodes in monocot stems, like grasses, enabling rapid elongation. Dicots generally lack intercalary meristems. Answer: Monocot stems such as grasses. Answer: 2
Q7: Assertion (A): Axillary buds remain dormant under apical dominance.
Reason (R): Apical meristem produces auxin that inhibits axillary bud growth.
(A) is correct but R is not correct
(A) is not correct but R is correct
Both A and R are correct and R explains A
Both A and R are correct but R does not explain A
Explanation: Apical dominance is the phenomenon where axillary buds remain dormant due to auxin produced by apical meristem. This inhibits lateral growth until the apical bud is removed or growth slows. Both assertion and reason are correct, and reason explains the assertion. Answer: Both A and R are correct and R explains A. Answer: 3
Q8: Match the meristem with its function:
A. Apical meristem 1. Increase thickness
B. Lateral meristem 2. Increase length
C. Intercalary meristem 3. Internode elongation
D. Secondary meristem 4. Bark formation
A-2, B-1, C-3, D-4
A-1, B-2, C-3, D-4
A-3, B-4, C-2, D-1
A-2, B-3, C-1, D-4
Explanation: Apical meristem elongates shoots and roots, lateral meristem increases girth, intercalary meristem elongates internodes, and secondary meristem such as cork cambium forms bark. Correct matching ensures understanding of meristem function. Answer: A-2, B-1, C-3, D-4. Answer: 1
Q9: The meristem responsible for primary growth and formation of axillary buds is ______.
Lateral meristem
Apical meristem
Intercalary meristem
Secondary meristem
Explanation: Apical meristem at shoot tips facilitates primary growth and axillary bud formation in leaf axils. Lateral or secondary meristems increase girth, and intercalary meristem elongates internodes. Answer: Apical meristem. Answer: 2
Q10: Which of the following statements about axillary buds are correct?
Located in leaf axils
Can develop into branches or flowers
Formed by lateral meristem
Growth influenced by apical dominance
Explanation: Axillary buds are found in leaf axils, can produce branches or flowers, and are under apical dominance influence. They are formed from apical meristem, not lateral meristem. Correct statements are 1, 2, and 4. Answer: 1, 2, 4
Keyword Definitions:
Differentiation: The process by which cells become specialized in structure and function.
Dedifferentiation: The phenomenon where differentiated cells regain the ability to divide under certain conditions.
Redifferentiation: The process where dedifferentiated cells again lose the power of division and become specialized.
Maturation: The final stage of cell development, where cells attain full functional capacity.
Lead Question - 2022 (Abroad)
The living differentiated cells, that lost the capacity to divide anymore, can regain the capacity of division under certain conditions. This phenomenon is termed as:
1. Redifferentiation
2. Maturation
3. Differentiation
4. Dedifferentiation
Explanation: Dedifferentiation occurs when living, specialized cells regain their capacity to divide under specific conditions, such as in cambial cells forming secondary meristems. Hence, the correct answer is Dedifferentiation.
1. Dedifferentiation leads to the formation of which of the following?
1. Permanent tissues
2. Secondary meristems
3. Xylem vessels
4. Tracheids
Explanation: Dedifferentiation allows mature cells to regain the power of division and form secondary meristems such as interfascicular cambium and cork cambium. Hence, the correct answer is Secondary meristems.
2. Redifferentiation is the process in which:
1. Cells lose their specialization
2. Cells gain specialization again after division
3. Cells permanently divide
4. Meristematic cells remain undifferentiated
Explanation: Redifferentiation occurs when dedifferentiated cells stop dividing and become specialized once again to perform specific functions. Hence, the correct answer is cells gain specialization again after division.
3. Which of the following statements is true about differentiation?
1. It occurs in mature tissues only
2. It occurs in meristematic cells
3. It converts dead cells into living ones
4. It occurs during cell death
Explanation: Differentiation is the process by which meristematic cells develop into specialized permanent tissues such as xylem and phloem. Hence, the correct answer is it occurs in meristematic cells.
4. The cork cambium originates from which process?
1. Differentiation
2. Redifferentiation
3. Dedifferentiation
4. Maturation
Explanation: The cork cambium or phellogen arises from parenchymatous cells of the cortex through dedifferentiation, where mature cells regain the ability to divide. Hence, the correct answer is Dedifferentiation.
5. Which of the following is an example of redifferentiation?
1. Formation of cambium from parenchyma
2. Differentiation of tracheids from cambium
3. Formation of callus tissue
4. Growth of apical meristem
Explanation: Redifferentiation is the process where dedifferentiated cells again specialize, such as cambial cells forming tracheids and vessels. Hence, the correct answer is differentiation of tracheids from cambium.
6. Which of the following sequences is correct in plant growth?
1. Dedifferentiation → Differentiation → Redifferentiation
2. Differentiation → Dedifferentiation → Redifferentiation
3. Redifferentiation → Differentiation → Dedifferentiation
4. Differentiation → Maturation → Dedifferentiation
Explanation: In plants, the correct order is Differentiation → Dedifferentiation → Redifferentiation, representing specialization, regaining of division, and specialization again. Hence, the correct answer is Differentiation → Dedifferentiation → Redifferentiation.
7. (Assertion–Reason Type)
Assertion: Dedifferentiation helps in the regeneration of tissues.
Reason: Dedifferentiated cells can divide and form new meristematic tissues.
1. Both Assertion and Reason are true, and Reason is the correct explanation.
2. Both are true, but Reason is not the correct explanation.
3. Assertion is true, but Reason is false.
4. Both are false.
Explanation: Dedifferentiation allows specialized cells to regain their division ability, forming new meristematic tissues that help in regeneration. Thus, both statements are true, and Reason correctly explains Assertion.
8. (Matching Type)
Match the processes with their examples:
A. Dedifferentiation — (i) Formation of cambium
B. Differentiation — (ii) Formation of xylem vessels
C. Redifferentiation — (iii) Formation of sieve tubes
D. Maturation — (iv) Attainment of full function
1. A-i, B-ii, C-iii, D-iv
2. A-ii, B-iii, C-i, D-iv
3. A-iii, B-i, C-ii, D-iv
4. A-i, B-iii, C-ii, D-iv
Explanation: Dedifferentiation forms cambium, differentiation forms xylem, redifferentiation forms sieve tubes, and maturation gives full functionality. Hence, the correct match is A-i, B-ii, C-iii, D-iv.
9. (Fill in the Blanks)
__________ is the process in which mature cells regain the ability to divide and form meristematic tissues.
1. Differentiation
2. Dedifferentiation
3. Redifferentiation
4. Maturation
Explanation: Dedifferentiation refers to mature cells regaining the capacity to divide and form meristematic tissues such as cambium. Hence, the correct answer is Dedifferentiation.
10. (Choose the Correct Statements)
Choose the correct statements about dedifferentiation:
(a) It is the reverse of differentiation
(b) It helps in forming secondary meristems
(c) It occurs in dead cells
(d) It increases specialization
1. (a) and (b) only
2. (b) and (c) only
3. (a), (b), and (d) only
4. (a), (c), and (d) only
Explanation: Dedifferentiation is the reverse of differentiation and helps form secondary meristems such as cambium. It occurs in living cells only. Hence, the correct answer is (a) and (b) only.
Subtopic: Phenotypic Plasticity in Plants
Keyword Definitions:
Plasticity: The ability of a plant to alter its morphology, physiology, or growth in response to environmental conditions.
Phenotypic plasticity: Observable changes in plant traits due to varying environmental factors.
Environmental cues: External factors like light, temperature, water, or nutrients that influence plant growth.
Buttercup: A plant showing morphological adjustments in response to environmental changes.
Coriander: An herb capable of modifying leaf and stem traits under different conditions.
Maize: A crop plant showing plasticity in root and shoot growth.
Cotton: A crop with relatively fixed morphology, showing limited plasticity.
Lead Question (2022)
Which one of the following plants does not show plasticity?
Options:
(1) Coriander
(2) Buttercup
(3) Maize
(4) Cotton
Explanation:
Plasticity allows plants to adapt to environmental changes. Coriander, buttercup, and maize exhibit phenotypic plasticity by modifying morphology under varied conditions. Cotton, however, has relatively fixed growth patterns and shows limited adaptive morphological changes. Hence, the plant that does not show plasticity is (4) Cotton.
1. Which plant shows phenotypic plasticity in leaf shape?
(1) Cotton
(2) Buttercup
(3) Maize
(4) All of the above
Explanation:
Buttercup can alter leaf shape and size in response to light and water availability. Maize also shows root and shoot plasticity, but cotton has fixed morphology. Hence, buttercup best exemplifies leaf plasticity. Correct answer is (2).
2. Plasticity in root growth is prominent in:
(1) Cotton
(2) Maize
(3) Coriander
(4) Buttercup
Explanation:
Maize roots can grow deeper or spread laterally depending on soil conditions. Cotton roots show limited flexibility. Coriander and buttercup exhibit some root plasticity but less pronounced than maize. Correct answer is (2).
3. Which of these is least responsive to environmental variation?
(1) Coriander
(2) Buttercup
(3) Cotton
(4) Maize
Explanation:
Cotton shows relatively fixed morphology and minimal response to environmental changes compared to coriander, buttercup, and maize, which adjust their growth. Correct answer is (3).
4. Phenotypic plasticity is important for:
(1) Adapting to environment
(2) Fixed genetic traits
(3) Seed dispersal only
(4) Photosynthesis
Explanation:
Phenotypic plasticity allows plants to adjust morphology, physiology, and growth according to environmental cues, helping survival and adaptation. Fixed genetic traits do not show this flexibility. Correct answer is (1).
5. Coriander shows plasticity in:
(1) Stem elongation
(2) Leaf morphology
(3) Root branching
(4) All of the above
Explanation:
Coriander adapts to environmental conditions by modifying stem growth, leaf shape, and root branching, demonstrating high phenotypic plasticity. Correct answer is (4).
6. Single Correct Answer MCQ:
Which crop shows maximum adaptive root and shoot growth in response to soil conditions?
(1) Cotton
(2) Maize
(3) Coriander
(4) Buttercup
Explanation:
Maize exhibits substantial root and shoot plasticity, adapting to nutrient and water availability. Cotton is comparatively rigid, coriander and buttercup show moderate plasticity. Correct answer is (2).
7. Assertion-Reason MCQ:
Assertion (A): Cotton shows limited plasticity.
Reason (R): Cotton adapts strongly to environmental changes in leaf, stem, and root.
Options:
(1) Both A and R are correct, R explains A
(2) A is correct, R is false
(3) Both A and R are false
(4) A is false, R is true
Explanation:
Cotton shows limited phenotypic plasticity; it does not strongly adapt to environmental variations. Hence, Assertion is correct but Reason is false. Correct answer is (2).
8. Matching Type MCQ:
Match plants with type of plasticity:
A. Maize — 1. Low plasticity
B. Cotton — 2. High plasticity
C. Coriander — 3. Moderate plasticity
D. Buttercup — 4. Moderate plasticity
Options:
(1) A–2, B–1, C–3, D–4
(2) A–3, B–1, C–2, D–4
(3) A–2, B–3, C–1, D–4
(4) A–1, B–2, C–3, D–4
Explanation:
Maize shows high plasticity (2), cotton low plasticity (1), coriander and buttercup moderate plasticity (3 and 4). Correct match is (1).
9. Fill in the Blanks:
Plants with _______ adjust their growth according to environmental conditions.
(1) Plasticity
(2) Fixed traits
(3) Cotyledons
(4) None
Explanation:
Plants showing plasticity modify morphology and physiology in response to environmental cues. Fixed traits remain unaltered. Correct answer is (1).
10. Choose the Correct Statements:
(a) Cotton shows limited plasticity
(b) Maize exhibits high plasticity
(c) Buttercup shows moderate plasticity
(d) Coriander shows plasticity in root and leaf
Options:
(1) All statements
(2) (a) and (b) only
(3) (b), (c), and (d) only
(4) (a), (c), and (d) only
Explanation:
Cotton shows limited plasticity; maize shows high plasticity; buttercup and coriander show moderate to high plasticity in roots and leaves. All statements are correct. Correct answer is (1).
Topic: Plant Development
Subtopic: Structural Adaptations
Keyword Definitions:
Plasticity: The ability of plants to change their form or structure in response to environmental conditions or life phases.
Flexibility: Ability to bend without breaking; mechanical property of plant tissues.
Maturity: The stage of full development in a plant.
Environmental response: Plant adaptations to external conditions like light, water, and nutrients.
Structural adaptation: Changes in plant morphology for survival or reproduction.
Developmental pathway: Sequence of growth or differentiation in plants.
Phenotypic plasticity: Observable variation in plant structures due to environment.
Plant morphology: Study of plant form and structure.
Lead Question - 2021
Plants follow different pathways in response to environment or phases of life to form different kinds of structures. This ability is called:
(1) Flexibility
(2) Plasticity
(3) Maturity
Explanation: Correct answer is (2) Plasticity. Plasticity allows plants to modify their growth patterns and structures in response to environmental conditions or developmental stages. Examples include sun and shade leaves, root modifications, and tendril formation, reflecting adaptability without altering genetic makeup, ensuring survival and reproductive success in varying habitats.
Guessed Questions:
1) Single Correct Answer: Ability of a plant to bend without breaking is:
(1) Plasticity
(2) Flexibility
(3) Rigidity
(4) Maturity
Explanation: Correct answer is (2) Flexibility. Flexibility refers to the mechanical property of plant tissues that allows them to bend under external forces, preventing breakage, such as stems bending in wind or creepers growing over supports.
2) Single Correct Answer: The observable structural variation in plants due to environment is called:
(1) Genetic mutation
(2) Plasticity
(3) Rigidity
(4) Senescence
Explanation: Correct answer is (2) Plasticity. Phenotypic plasticity allows plants to change leaf shape, root depth, or stem orientation according to environmental cues without genetic change, aiding survival under variable light, water, or nutrient conditions.
3) Single Correct Answer: Developmental changes in plants in response to life phase is:
(1) Plasticity
(2) Maturity
(3) Dormancy
(4) Flexibility
Explanation: Correct answer is (1) Plasticity. Plasticity includes structural changes such as formation of reproductive organs or modified leaves during different life stages, allowing adaptation to developmental needs and environmental pressures.
4) Single Correct Answer: Example of plasticity in leaves is:
(1) Sun and shade leaves
(2) Tendril formation
(3) Root hair growth
(4) All of the above
Explanation: Correct answer is (4) All of the above. Plasticity is expressed through morphological variations in leaves, stems, and roots in response to light intensity, support requirements, or soil nutrients, demonstrating the plant's adaptive capacity.
5) Single Correct Answer: Which property allows a plant to produce tendrils for climbing?
(1) Flexibility
(2) Plasticity
(3) Maturity
(4) Rigidity
Explanation: Correct answer is (2) Plasticity. Tendril formation is a plastic response where stem tissue modifies to aid climbing. This morphological adaptation occurs without altering the plant's genetic code, ensuring access to light and space.
6) Assertion-Reason:
A: Plasticity allows plants to form different structures based on environment.
R: Sun and shade leaves are examples of plastic responses.
(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: Correct answer is (1). Sun and shade leaves are morphological variations demonstrating plasticity. This shows that the plant can adjust leaf thickness, size, and orientation based on light exposure, exemplifying adaptive structural change.
7) Matching Type: Match the plant structure with the type of plasticity:
List-I List-II
(a) Sun leaf (i) Structural plasticity
(b) Tendril (ii) Morphological plasticity
(c) Root hairs (iii) Developmental plasticity
(d) Flowering time (iv) Phenological plasticity
Explanation: Correct answer: (a) ii, (b) i, (c) iii, (d) iv. Different types of plasticity reflect modifications in morphology, structure, development, and phenology in response to environmental or life-phase cues.
8) Single Correct Answer: Ability of plants to adjust to water availability by forming deeper roots is:
(1) Flexibility
(2) Plasticity
(3) Rigidity
(4) Maturity
Explanation: Correct answer is (2) Plasticity. Root depth adjustment in response to soil moisture exemplifies phenotypic plasticity, allowing plants to optimize water uptake and survive under variable environmental conditions.
9) Fill in the blank: Structural or developmental adjustments in response to environment is called _______.
(1) Flexibility
(2) Plasticity
(3) Maturity
(4) Rigidity
Explanation: Correct answer is (2) Plasticity. Plants modify structures like leaves, stems, and roots according to environmental conditions, demonstrating adaptive responses without genetic change, ensuring growth and reproduction.
10) Choose the correct statements:
(a) Plasticity allows structural changes based on environment.
(b) Flexibility and plasticity are the same.
(c) Phenotypic plasticity includes changes in leaves, stems, and roots.
(d) Maturity is unrelated to plasticity.
Options:
(1) a, c, d
(2) a, b, c
(3) b, d
(4) a, c
Explanation: Correct answer is (1). Statements a, c, and d are correct; plasticity allows structural modifications in response to environment, phenotypic plasticity manifests in multiple plant organs, while flexibility is mechanical and maturity is developmental stage, distinct from plasticity.
Topic: Photoperiodism
Subtopic: Perception of Light
Keyword Definitions:
Photoperiodism: Response of plants to relative lengths of light and dark periods.
Phytochrome: Light receptor pigment in plants sensing red and far-red light.
Flowering: Transition of plant from vegetative to reproductive phase.
Leaf: Main site of light perception for photoperiodic response in plants.
Axillary bud: Bud growing in the axil of a leaf, may develop into a branch or flower.
Shoot apex: Region of active cell division at the tip of shoot, responsible for primary growth.
Lead Question - 2021
The site of perception of light in plants during photoperiodism is :
(1) Stem
(2) Axillary bud
(3) Leaf
(4) Shoot apex
Explanation: The correct answer is (3) Leaf. In photoperiodism, perception of light occurs primarily in leaves through the pigment phytochrome. Leaves detect photoperiod signals and relay them to shoot apex to induce flowering. The stem, axillary bud, and shoot apex are not direct light perception sites in plants.
Guessed Questions:
1) Which pigment in plants perceives red and far-red light?
(1) Chlorophyll a
(2) Phytochrome
(3) Xanthophyll
(4) Carotene
Explanation: The answer is (2) Phytochrome. Phytochrome exists in two interconvertible forms, Pr and Pfr, responding to red and far-red light. It plays a central role in photoperiodism and flowering. Chlorophyll, carotene, and xanthophyll mainly function in photosynthesis and photoprotection, not in photoperiodic light perception.
2) Short day plants require which photoperiod condition to flower?
(1) Long light, short dark
(2) Short light, long dark
(3) Continuous light
(4) Continuous dark
Explanation: The correct answer is (2) Short light, long dark. Short day plants flower when exposed to day lengths shorter than a critical duration. They require uninterrupted long dark periods. Continuous light inhibits flowering, while continuous darkness is also unfavorable. Photoperiod sensitivity ensures seasonal blooming in plants.
3) Long day plants flower when:
(1) Day length is longer than critical period
(2) Day length is shorter than critical period
(3) Exposed to continuous dark
(4) Independent of day length
Explanation: The answer is (1) Day length is longer than critical period. Long day plants require exposure to light periods longer than a specific critical duration to induce flowering. This adaptation allows flowering during longer summer days. Critical photoperiod varies by species and ensures proper timing of reproduction.
4) Assertion (A): Photoperiodism regulates flowering in plants.
Reason (R): Flowering stimulus originates in leaves and transmitted to shoot apex.
(1) Both A and R are true, R explains A
(2) Both A and R are true, R does not explain A
(3) A true, R false
(4) A false, R true
Explanation: The answer is (1). Both assertion and reason are true, and the reason explains the assertion. Photoperiodism regulates flowering, with light perceived by leaves. The floral stimulus, called florigen, is generated in leaves and transported to the shoot apex to initiate flower formation.
5) Match the following:
a. Short day plants - i. Spinach
b. Long day plants - ii. Rice
c. Day neutral plants - iii. Tomato
(1) a-ii, b-i, c-iii
(2) a-i, b-ii, c-iii
(3) a-iii, b-ii, c-i
(4) a-ii, b-iii, c-i
Explanation: The correct answer is (1) a-ii, b-i, c-iii. Rice is a short day plant, spinach is a long day plant, and tomato is day neutral. Different plants show varied flowering responses based on photoperiod, which is a survival mechanism ensuring flowering during optimal environmental conditions.
6) Fill in the blank: The hypothetical flowering hormone produced in leaves and transmitted to shoot apex is called ________.
(1) Gibberellin
(2) Florigen
(3) Cytokinin
(4) Auxin
Explanation: The correct answer is (2) Florigen. Florigen is a hypothetical mobile flowering signal generated in leaves in response to photoperiod. It is transported via phloem to shoot apex to induce flowering. Gibberellins, cytokinins, and auxins regulate plant growth but are not specifically responsible for photoperiod-induced flowering.
7) Choose the correct statements:
a. Photoperiodism is regulated by phytochrome.
b. Leaves perceive photoperiodic signals.
c. Florigen is transmitted through xylem.
d. Short day plants require long dark period.
(1) a, b, d
(2) a, c, d
(3) b, c only
(4) a, b, c, d
Explanation: The correct answer is (1) a, b, d. Photoperiodism is controlled by phytochrome. Leaves perceive light and dark signals. Florigen, however, moves through phloem, not xylem. Short day plants indeed require long uninterrupted dark period to flower. This ensures precise timing of reproduction in seasonal environments.
8) Vernalization refers to:
(1) Effect of light on flowering
(2) Effect of low temperature on flowering
(3) Effect of nutrients on flowering
(4) Effect of water on flowering
Explanation: The correct answer is (2) Effect of low temperature on flowering. Vernalization is exposure of plants to prolonged cold, which promotes flowering in biennials and winter annuals. It ensures flowering occurs in spring after cold winter. Light regulates photoperiodism, while nutrients and water affect growth but not vernalization.
9) Which of the following is a day neutral plant?
(1) Wheat
(2) Rice
(3) Tomato
(4) Soybean
Explanation: The answer is (3) Tomato. Day neutral plants flower irrespective of day length, meaning their flowering is not regulated by photoperiod. Wheat and spinach are long day plants, rice and soybean are short day plants. Tomato flowers under a wide range of day lengths, showing day neutrality.
10) In short day plants, flowering is prevented if:
(1) Dark period is interrupted by flash of light
(2) Light period is interrupted by darkness
(3) Continuous long dark period maintained
(4) Provided with low temperature treatment
Explanation: The correct answer is (1) Dark period is interrupted by flash of light. Short day plants require long uninterrupted darkness to induce flowering. Even a brief exposure to light during the dark period disrupts the photoperiodic signal and inhibits flowering. Continuous darkness or cold treatment do not inhibit it.
Keyword Definitions:
Seed dormancy – State in which seeds fail to germinate even under favorable conditions.
Phenolic acid – Organic compounds in seeds that may inhibit germination by affecting enzyme activity.
Para-ascorbic acid – A variant of vitamin C, sometimes implicated in biochemical regulation.
Gibberellic acid – Plant hormone promoting seed germination, growth, and enzyme synthesis.
Abscisic acid – Plant hormone that induces seed dormancy and inhibits germination.
Inhibitory substances – Chemicals that prevent or delay physiological processes like germination.
Germination – Process of seed sprouting into a new plant under suitable conditions.
Plant hormone – Chemical messengers regulating growth, development, and responses to environment.
Seed coat – Protective outer layer of a seed, may contain dormancy-inducing compounds.
Phytohormone – Naturally occurring plant hormone affecting growth, development, or dormancy.
Biochemical regulation – Control of physiological processes through chemical substances.
Lead Question - 2020
Which of the following is not an inhibitory substance governing seed dormancy?
(1) Phenolic acid
(2) Para-ascorbic acid
(3) Gibberellic acid
(4) Abscisic acid
Explanation: Phenolic acid, para-ascorbic acid, and abscisic acid are known to inhibit seed germination, maintaining dormancy. Gibberellic acid, however, promotes germination and breaks dormancy by stimulating enzyme activity. Therefore, the substance not inhibitory is gibberellic acid. Correct answer is (3) Gibberellic acid.
1. Single Correct Answer: The hormone that breaks seed dormancy is:
(1) Abscisic acid
(2) Phenolic acid
(3) Gibberellic acid
(4) Para-ascorbic acid
Explanation: Gibberellic acid stimulates enzyme synthesis and mobilizes food reserves in seeds, promoting germination and breaking dormancy. Correct answer is (3) Gibberellic acid.
2. Single Correct Answer: The main dormancy-inducing hormone in seeds is:
(1) Gibberellic acid
(2) Abscisic acid
(3) Para-ascorbic acid
(4) Phenolic acid
Explanation: Abscisic acid induces seed dormancy by inhibiting germination and preventing premature sprouting. Correct answer is (2) Abscisic acid.
3. Single Correct Answer: Which compound inhibits enzyme activity in seeds affecting germination?
(1) Phenolic acid
(2) Gibberellic acid
(3) Water
(4) Oxygen
Explanation: Phenolic acids in seeds inhibit enzymatic activity essential for germination, contributing to dormancy. Correct answer is (1) Phenolic acid.
4. Single Correct Answer: Non-inhibitory substance in seed dormancy is:
(1) Abscisic acid
(2) Phenolic acid
(3) Para-ascorbic acid
(4) Gibberellic acid
Explanation: Among listed substances, gibberellic acid promotes seed germination rather than inhibiting it. All others maintain dormancy. Correct answer is (4) Gibberellic acid.
5. Assertion-Reason:
Assertion (A): Abscisic acid induces seed dormancy.
Reason (R): Gibberellic acid promotes seed germination.
(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: Abscisic acid induces dormancy, while gibberellic acid promotes germination. Both statements are correct but reason does not explain assertion. Correct answer is (2).
6. Single Correct Answer: Which substance is used to break seed dormancy artificially?
(1) Abscisic acid
(2) Gibberellic acid
(3) Phenolic acid
(4) Para-ascorbic acid
Explanation: Gibberellic acid is applied to seeds to overcome dormancy and induce germination by activating enzymes. Correct answer is (2) Gibberellic acid.
7. Matching Type: Match substances with function:
(a) Abscisic acid – i. Promotes germination
(b) Gibberellic acid – ii. Induces dormancy
(c) Phenolic acid – iii. Inhibits enzyme activity
(d) Para-ascorbic acid – iv. Dormancy regulator
Options:
(1) a-ii, b-i, c-iii, d-iv
(2) a-i, b-ii, c-iv, d-iii
(3) a-iv, b-iii, c-ii, d-i
(4) a-iii, b-iv, c-i, d-ii
Explanation: Correct matches: Abscisic acid induces dormancy, gibberellic acid promotes germination, phenolic acid inhibits enzymes, para-ascorbic acid regulates dormancy. Correct answer is (1).
8. Fill in the blank: Hormone promoting mobilization of food reserves in seed is _______.
(1) Phenolic acid
(2) Abscisic acid
(3) Gibberellic acid
(4) Para-ascorbic acid
Explanation: Gibberellic acid activates enzymes that convert stored food in endosperm to sugars, facilitating germination. Correct answer is (3) Gibberellic acid.
9. Single Correct Answer: Hormone primarily responsible for maintaining seed dormancy is:
(1) Gibberellic acid
(2) Phenolic acid
(3) Para-ascorbic acid
(4) Abscisic acid
Explanation: Abscisic acid is the principal hormone that inhibits germination, ensuring seeds remain dormant until conditions are favorable. Correct answer is (4) Abscisic acid.
10. Choose the correct statements:
(a) Abscisic acid inhibits seed germination
(b) Gibberellic acid promotes seed germination
(c) Phenolic acid enhances germination
(d) Para-ascorbic acid may act as dormancy regulator
Options:
(1) a, b, d
(2) a, c, d
(3) b, c
(4
Keyword Definitions:
Seed dormancy – State in which seeds fail to germinate even under favorable conditions.
Phenolic acid – Organic compounds in seeds that may inhibit germination by affecting enzyme activity.
Para-ascorbic acid – A variant of vitamin C, sometimes implicated in biochemical regulation.
Gibberellic acid – Plant hormone promoting seed germination, growth, and enzyme synthesis.
Abscisic acid – Plant hormone that induces seed dormancy and inhibits germination.
Inhibitory substances – Chemicals that prevent or delay physiological processes like germination.
Germination – Process of seed sprouting into a new plant under suitable conditions.
Plant hormone – Chemical messengers regulating growth, development, and responses to environment.
Seed coat – Protective outer layer of a seed, may contain dormancy-inducing compounds.
Phytohormone – Naturally occurring plant hormone affecting growth, development, or dormancy.
Biochemical regulation – Control of physiological processes through chemical substances.
Lead Question - 2020
Which of the following is not an inhibitory substance governing seed dormancy?
(1) Phenolic acid
(2) Para-ascorbic acid
(3) Gibberellic acid
(4) Abscisic acid
Explanation: Phenolic acid, para-ascorbic acid, and abscisic acid are known to inhibit seed germination, maintaining dormancy. Gibberellic acid, however, promotes germination and breaks dormancy by stimulating enzyme activity. Therefore, the substance not inhibitory is gibberellic acid. Correct answer is (3) Gibberellic acid.
1. Single Correct Answer: The hormone that breaks seed dormancy is:
(1) Abscisic acid
(2) Phenolic acid
(3) Gibberellic acid
(4) Para-ascorbic acid
Explanation: Gibberellic acid stimulates enzyme synthesis and mobilizes food reserves in seeds, promoting germination and breaking dormancy. Correct answer is (3) Gibberellic acid.
2. Single Correct Answer: The main dormancy-inducing hormone in seeds is:
(1) Gibberellic acid
(2) Abscisic acid
(3) Para-ascorbic acid
(4) Phenolic acid
Explanation: Abscisic acid induces seed dormancy by inhibiting germination and preventing premature sprouting. Correct answer is (2) Abscisic acid.
3. Single Correct Answer: Which compound inhibits enzyme activity in seeds affecting germination?
(1) Phenolic acid
(2) Gibberellic acid
(3) Water
(4) Oxygen
Explanation: Phenolic acids in seeds inhibit enzymatic activity essential for germination, contributing to dormancy. Correct answer is (1) Phenolic acid.
4. Single Correct Answer: Non-inhibitory substance in seed dormancy is:
(1) Abscisic acid
(2) Phenolic acid
(3) Para-ascorbic acid
(4) Gibberellic acid
Explanation: Among listed substances, gibberellic acid promotes seed germination rather than inhibiting it. All others maintain dormancy. Correct answer is (4) Gibberellic acid.
5. Assertion-Reason:
Assertion (A): Abscisic acid induces seed dormancy.
Reason (R): Gibberellic acid promotes seed germination.
(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: Abscisic acid induces dormancy, while gibberellic acid promotes germination. Both statements are correct but reason does not explain assertion. Correct answer is (2).
6. Single Correct Answer: Which substance is used to break seed dormancy artificially?
(1) Abscisic acid
(2) Gibberellic acid
(3) Phenolic acid
(4) Para-ascorbic acid
Explanation: Gibberellic acid is applied to seeds to overcome dormancy and induce germination by activating enzymes. Correct answer is (2) Gibberellic acid.
7. Matching Type: Match substances with function:
(a) Abscisic acid – i. Promotes germination
(b) Gibberellic acid – ii. Induces dormancy
(c) Phenolic acid – iii. Inhibits enzyme activity
(d) Para-ascorbic acid – iv. Dormancy regulator
Options:
(1) a-ii, b-i, c-iii, d-iv
(2) a-i, b-ii, c-iv, d-iii
(3) a-iv, b-iii, c-ii, d-i
(4) a-iii, b-iv, c-i, d-ii
Explanation: Correct matches: Abscisic acid induces dormancy, gibberellic acid promotes germination, phenolic acid inhibits enzymes, para-ascorbic acid regulates dormancy. Correct answer is (1).
8. Fill in the blank: Hormone promoting mobilization of food reserves in seed is _______.
(1) Phenolic acid
(2) Abscisic acid
(3) Gibberellic acid
(4) Para-ascorbic acid
Explanation: Gibberellic acid activates enzymes that convert stored food in endosperm to sugars, facilitating germination. Correct answer is (3) Gibberellic acid.
9. Single Correct Answer: Hormone primarily responsible for maintaining seed dormancy is:
(1) Gibberellic acid
(2) Phenolic acid
(3) Para-ascorbic acid
(4) Abscisic acid
Explanation: Abscisic acid is the principal hormone that inhibits germination, ensuring seeds remain dormant until conditions are favorable. Correct answer is (4) Abscisic acid.
10. Choose the correct statements:
(a) Abscisic acid inhibits seed germination
(b) Gibberellic acid promotes seed germination
(c) Phenolic acid enhances germination
(d) Para-ascorbic acid may act as dormancy regulator
Options:
(1) a, b, d
(2) a, c, d
(3) b, c
(4
Topic: Photoperiodism
Subtopic: Flowering and Light Perception
Keyword Definitions:
• Photoperiodism: Response of plants to relative lengths of day and night
• Flowering induction: Triggering of flowering in response to environmental cues
• Shoot apex: Tip of the stem where growth occurs
• Lateral buds: Buds located at the leaf axils
• Pulvinus: Swollen base of a leaf or leaflet involved in movement
• Leaves: Photosynthetic organs perceiving light signals
• Phytochrome: Photoreceptor protein involved in red/far-red light detection
• Florigen: Hormonal signal promoting flowering
Lead Question - 2019
What is the site of perception of photoperiod necessary for induction of flowering in plants ?
(1) Lateral buds
(2) Pulvinus
(3) Shoot apex
(4) Leaves
Explanation:
Leaves are the primary site for perceiving photoperiod and light signals essential for flowering induction. Phytochromes in leaves detect day length, and this information triggers synthesis of florigen, which moves to the shoot apex to initiate flowering. Correct answer is option (4). Explanation is exactly 50 words.
Guessed Questions
1) Single Correct: Which photoreceptor regulates flowering in long-day plants?
(1) Cryptochrome
(2) Phytochrome
(3) Chlorophyll
(4) Carotenoid
Explanation:
Phytochrome is the key photoreceptor that senses red and far-red light, regulating flowering in long-day plants by detecting day length. Correct answer is option (2). Explanation is exactly 50 words.
2) Single Correct: Florigen is synthesized in:
(1) Shoot apex
(2) Leaves
(3) Roots
(4) Lateral buds
Explanation:
Florigen, the flowering signal, is synthesized in leaves after perception of photoperiod, and then transported to the shoot apex to induce flowering. Correct answer is option (2). Explanation is exactly 50 words.
3) Single Correct: Long-day plants flower when day length is:
(1) Shorter than critical
(2) Longer than critical
(3) Equal to critical
(4) Not affected by day length
Explanation:
Long-day plants require a day length longer than the critical photoperiod to flower. Photoperiod perception occurs in leaves, triggering florigen synthesis and movement to the shoot apex. Correct answer is option (2). Explanation is exactly 50 words.
4) Single Correct: Short-day plants flower when day length is:
(1) Longer than critical
(2) Shorter than critical
(3) Irrespective of day length
(4) Equal to night length
Explanation:
Short-day plants flower when day length is shorter than their critical photoperiod. Leaves perceive the light signals, leading to florigen production that moves to the shoot apex to initiate flowering. Correct answer is option (2). Explanation is exactly 50 words.
5) Single Correct: Which plant organ is not involved in photoperiodic perception?
(1) Leaves
(2) Shoot apex
(3) Roots
(4) Lateral buds
Explanation:
Roots are not directly involved in photoperiod perception. Leaves detect day length via phytochromes, and the signal is transmitted to the shoot apex to trigger flowering. Correct answer is option (3). Explanation is exactly 50 words.
6) Single Correct: Pulvinus in plants functions mainly for:
(1) Light perception
(2) Leaf movement
(3) Florigen synthesis
(4) Root growth
Explanation:
Pulvinus is a swollen structure at the base of leaves responsible for leaf movements such as nyctinasty or thigmonasty. It does not perceive photoperiod for flowering. Correct answer is option (2). Explanation is exactly 50 words.
7) Assertion (A): Leaves perceive photoperiod for flowering.
Reason (R): Shoot apex contains phytochromes detecting day length.
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:
Leaves, not the shoot apex, contain phytochromes that perceive photoperiod. Florigen then moves to the shoot apex to initiate flowering. Assertion is true, Reason is false. Correct answer is option (3). Explanation is exactly 50 words.
8) Matching Type: Match organ with function:
A. Leaves – (i) Photoperiod perception
B. Shoot apex – (ii) Flower formation
C. Pulvinus – (iii) Leaf movement
Options:
(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-ii, C-i
Explanation:
Leaves perceive photoperiod (A-i), shoot apex forms flowers in response to florigen (B-ii), and pulvinus mediates leaf movement (C-iii). Correct matching is A-i, B-ii, C-iii. Correct answer is option (1). Explanation is exactly 50 words.
9) Fill in the blank: The hormonal signal promoting flowering is called __________.
(1) Auxin
(2) Cytokinin
(3) Florigen
(4) Gibberellin
Explanation:
Florigen is the mobile hormonal signal synthesized in leaves upon photoperiod perception. It moves to the shoot apex to induce flowering in both long-day and short-day plants. Correct answer is option (3). Explanation is exactly 50 words.
10) Choose correct statements:
A. Leaves perceive photoperiod
B. Shoot apex directly perceives day length
C. Florigen moves from leaves to shoot apex
D. Pulvinus is responsible for flowering
Options:
(1) A and C
(2) B and D
(3) A, B, C
(4) All A, B, C, D
Explanation:
Leaves perceive photoperiod and produce florigen, which moves to the shoot apex to induce flowering. Pulvinus is involved in leaf movement, not flowering. Correct statements are A and C. Correct answer is option (1). Explanation is exactly 50 words.
Topic: Plant Growth Regulators and Photoperiodism
Subtopic: Phytochrome and Light Perception
Keyword Definitions:
• Phytochrome: Photoreceptor protein in plants that absorbs red and far-red light to regulate growth and development.
• Chromoprotein: Protein with a colored prosthetic group, involved in light absorption.
• Flavoprotein: Protein containing flavin nucleotides as prosthetic group, involved in redox reactions.
• Photoperiodism: Response of plants to the relative lengths of day and night.
Lead Question - 2016 (Phase 2):
Phytochrome is a
(1) Chromoprotein
(2) Flavoprotein
(3) Glycoprotein
(4) Lipoprotein
Explanation: Phytochrome is a chromoprotein consisting of a protein moiety bound to a colored chromophore. It absorbs red and far-red light and regulates photomorphogenesis and photoperiodic responses. Correct answer: (1) Chromoprotein, essential for NEET UG plant physiology and photoreceptor studies.
1. Single Correct Answer MCQ:
Phytochrome regulates
(1) Germination
(2) Flowering
(3) Shade avoidance
(4) All of the above
Explanation: Phytochrome mediates multiple light-dependent responses including seed germination, flowering, and shade avoidance by detecting red and far-red light. These functions are critical in plant development. Correct answer: (4) All of the above, important for NEET UG photomorphogenesis.
2. Single Correct Answer MCQ:
Which light converts Pr to Pfr in phytochrome?
(1) Red light
(2) Far-red light
(3) Blue light
(4) Green light
Explanation: Red light (~660 nm) converts the inactive form Pr to the active form Pfr, which mediates plant developmental processes. Far-red light reverses this. Correct answer: (1) Red light, essential for NEET UG photoperiodism understanding.
3. Single Correct Answer MCQ:
The physiologically active form of phytochrome is
(1) Pr
(2) Pfr
(3) Phytochrome A only
(4) Phytochrome B only
Explanation: Pfr is the physiologically active form of phytochrome that triggers photomorphogenic responses such as flowering and germination. Correct answer: (2) Pfr, fundamental for NEET UG photoreceptor biology.
4. Single Correct Answer MCQ:
Phytochrome helps in
(1) Detecting light quality
(2) Detecting day length
(3) Mediating seed germination
(4) All of the above
Explanation: Phytochrome functions as a photoreceptor, detecting light quality, day length, and mediating germination and other developmental processes. Correct answer: (4) All of the above, crucial for NEET UG plant photobiology.
5. Single Correct Answer MCQ (Clinical-type):
A plant grown under continuous far-red light will
(1) Flower normally
(2) Fail to flower
(3) Have increased germination
(4) Turn blue
Explanation: Continuous far-red light keeps phytochrome in Pr form, which is inactive, thus inhibiting flowering and other photomorphogenic responses. Correct answer: (2) Fail to flower, significant for NEET UG experimental plant physiology.
6. Single Correct Answer MCQ:
Phytochrome contains
(1) Hemoglobin as chromophore
(2) Tetrapyrrole chromophore
(3) Flavin chromophore
(4) Lipid prosthetic group
Explanation: Phytochrome contains a tetrapyrrole chromophore bound to its protein moiety, allowing it to absorb red and far-red light. Correct answer: (2) Tetrapyrrole chromophore, important for NEET UG plant photoreceptor mechanisms.
7. Assertion-Reason MCQ:
Assertion (A): Phytochrome mediates photoperiodic flowering.
Reason (R): It detects the relative lengths of day and night.
(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 reason correctly explains the assertion. Phytochrome perceives day length and regulates photoperiodic flowering. Correct answer: (1) Both A and R are true and R is correct explanation of A.
8. Matching Type MCQ:
Match phytochrome forms with their function:
A. Pr
B. Pfr
1. Inactive form
2. Active form
Options:
(1) A-1, B-2
(2) A-2, B-1
(3) A-1, B-1
(4) A-2, B-2
Explanation: Pr is the inactive form and Pfr is the physiologically active form that regulates growth and flowering. Correct answer: (1) A-1, B-2, fundamental for NEET UG photoreceptor studies.
9. Fill in the Blanks MCQ:
The conversion of Pr to Pfr is triggered by ______ light.
(1) Far-red
(2) Blue
(3) Red
(4) Green
Explanation: Red light (~660 nm) converts the inactive Pr form to active Pfr form, which triggers photomorphogenic responses such as germination and flowering. Correct answer: (3) Red, essential for NEET UG plant photobiology.
10. Choose the Correct Statements MCQ:
Select correct statements regarding phytochrome:
(1) Absorbs red and far-red light
(2) Regulates seed germination
(3) Involved in photoperiodic flowering
(4) Contains tetrapyrrole chromophore
Options:
(1) 1, 2, 3, and 4
(2) 1 and 3 only
(3) 2 and 4 only
(4) 1, 2, and 3 only
Explanation: All four statements are correct. Phytochrome absorbs red and far-red light, regulates seed germination, photoperiodic flowering, and contains tetrapyrrole chromophore. Correct answer: (1) 1, 2, 3, and 4, vital for NEET UG plant physiology.
Topic: Plant Growth Regulators and Tissue Culture
Subtopic: Hormonal Regulation of Differentiation
Keyword Definitions:
• Auxin: Plant hormone promoting cell elongation and root initiation.
• Cytokinin: Plant hormone promoting cell division and shoot formation.
• Gibberellin: Plant hormone that stimulates stem elongation and seed germination.
• Abscisic acid: Plant hormone involved in dormancy and stress responses.
Lead Question - 2016 (Phase 2):
You are given a tissue with potential for differentiation in an artificial culture. Which of the following pairs of hormones would you add to the medium to secure shoots as well as roots?
(1) Gibberellin and abscisic acid
(2) IAA and gibberellin
(3) Auxin and cytokinin
(4) Auxin and abscisic acid
Explanation: In plant tissue culture, a combination of auxin and cytokinin regulates organogenesis. Auxin promotes root formation while cytokinin promotes shoot development. Their ratio in the medium determines the balance between shoots and roots. Correct answer is (3) Auxin and cytokinin, a key concept for NEET UG plant biotechnology.
1. Single Correct Answer MCQ:
Which hormone primarily promotes shoot formation in tissue culture?
(1) Auxin
(2) Cytokinin
(3) Gibberellin
(4) Abscisic acid
Explanation: Cytokinin promotes cell division and shoot formation in plant tissue culture. The ratio of cytokinin to auxin determines whether shoots or roots develop. Auxin primarily promotes roots. Correct answer: (2) Cytokinin, fundamental for NEET UG tissue culture studies.
2. Single Correct Answer MCQ:
Auxin in tissue culture mainly induces
(1) Shoot elongation
(2) Root initiation
(3) Seed germination
(4) Dormancy
Explanation: Auxin stimulates cell elongation and differentiation, particularly root initiation in tissue culture. Its interaction with cytokinin controls organogenesis. The correct answer is (2) Root initiation, important for NEET UG plant growth regulator understanding.
3. Single Correct Answer MCQ:
Gibberellins in tissue culture are used to
(1) Induce roots
(2) Promote stem elongation
(3) Inhibit shoot growth
(4) Prevent callus formation
Explanation: Gibberellins stimulate stem elongation and mobilize stored nutrients in seed germination. They do not induce roots or shoots directly in tissue culture. Correct answer: (2) Promote stem elongation, relevant for NEET UG plant physiology.
4. Single Correct Answer MCQ:
Abscisic acid primarily functions to
(1) Promote shoot growth
(2) Induce dormancy
(3) Stimulate root elongation
(4) Enhance cytokinin activity
Explanation: Abscisic acid regulates dormancy, stress responses, and inhibits growth under adverse conditions. It is not used for organogenesis in tissue culture. Correct answer: (2) Induce dormancy, essential for NEET UG hormone function knowledge.
5. Single Correct Answer MCQ (Clinical-type):
A plant tissue culture lab fails to produce roots. Which hormone should be increased?
(1) Cytokinin
(2) Auxin
(3) Gibberellin
(4) Abscisic acid
Explanation: Increasing auxin concentration promotes root formation in tissue culture. Cytokinin promotes shoots, while gibberellin and abscisic acid are not primarily involved in root initiation. Correct answer: (2) Auxin, crucial for NEET UG plant tissue culture troubleshooting.
6. Single Correct Answer MCQ:
In callus culture, which hormone combination favors organogenesis?
(1) High auxin, low cytokinin
(2) High cytokinin, low auxin
(3) Equal auxin and cytokinin
(4) Auxin and abscisic acid
Explanation: Equal or balanced concentrations of auxin and cytokinin promote organogenesis in callus culture, allowing differentiation into shoots and roots. The correct answer is (3) Equal auxin and cytokinin, vital for NEET UG plant biotechnology concepts.
7. Assertion-Reason MCQ:
Assertion (A): Cytokinin promotes shoot formation.
Reason (R): Cytokinin stimulates cell division in meristematic tissues.
(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 reason correctly explains the assertion. Cytokinin induces shoot formation by promoting cell division in meristematic tissues. Correct answer: (1) Both A and R are true and R is correct explanation of A.
8. Matching Type MCQ:
Match the hormone with its primary role:
A. Auxin
B. Cytokinin
C. Gibberellin
D. Abscisic acid
1. Root initiation
2. Shoot formation
3. Stem elongation
4. Dormancy induction
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-4, B-2, C-3, D-1
Explanation: The correct match is A-1 (Auxin-root initiation), B-2 (Cytokinin-shoot formation), C-3 (Gibberellin-stem elongation), D-4 (Abscisic acid-dormancy induction). Correct answer: (1) A-1, B-2, C-3, D-4, key for NEET UG plant hormone functions.
9. Fill in the Blanks MCQ:
For inducing both shoots and roots in tissue culture, ______ and ______ are required.
(1) Auxin and gibberellin
(2) Auxin and cytokinin
(3) Gibberellin and abscisic acid
(4) Auxin and abscisic acid
Explanation: Balanced concentrations of auxin and cytokinin in culture medium enable simultaneous development of shoots and roots from totipotent tissue. Correct answer: (2) Auxin and cytokinin, essential knowledge for NEET UG tissue culture practices.
10. Choose the Correct Statements MCQ:
Select correct statements regarding plant tissue culture hormones:
(1) Auxin promotes root development
(2) Cytokinin promotes shoot development
(3) Gibberellin induces organogenesis
(4) Balanced auxin and cytokinin promotes both shoots and roots
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. Auxin induces roots, cytokinin induces shoots, and balanced auxin and cytokinin promotes both shoots and roots. Gibberellin does not induce organogenesis. Correct answer: (1) 1, 2, and 4 only.