Plant Growth & Development

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:

1. Lateral meristem

2. Secondary meristem

3. Apical meristem

4. 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?

1. Apical meristem

2. Intercalary meristem

3. Lateral meristem

4. 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:

1. Primary growth

2. Secondary growth

3. Leaf formation

4. 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:

1. Axillary buds

2. Apical buds

3. Accessory buds

4. 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?

1. Apical meristem

2. Lateral meristem

3. Intercalary meristem

4. 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:

1. Roots

2. Leaves

3. Branches or flowers

4. 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:

1. Dicot stems

2. Monocot stems such as grasses

3. Roots

4. 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.

1. (A) is correct but R is not correct

2. (A) is not correct but R is correct

3. Both A and R are correct and R explains A

4. Both A and R are correct but R does not explain A

Explanation: 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

1. A-2, B-1, C-3, D-4

2. A-1, B-2, C-3, D-4

3. A-3, B-4, C-2, D-1

4. 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 ______.

1. Lateral meristem

2. Apical meristem

3. Intercalary meristem

4. 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?

1. Located in leaf axils

2. Can develop into branches or flowers

3. Formed by lateral meristem

4. 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

Topic: Cellular Growth and Differentiation

Subtopic: Dedifferentiation and Redifferentiation

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.

Topic: Seed Dormancy and Germination

Subtopic: Inhibitory Substances in Seed Dormancy

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: Seed Dormancy and Germination

Subtopic: Inhibitory Substances in Seed Dormancy

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.