Part 7 – Plant Growth & Development – Complex NEET-Oriented Questions

Q1. In tissue culture, a callus develops. To induce roots from this callus, the required hormone ratio is:

a) High auxin : Low cytokinin
b) Low auxin : High cytokinin
c) Equal auxin : Equal cytokinin
d) High gibberellin : Low auxin

Answer: a) High auxin : Low cytokinin

a) High auxin : Low cytokinin – Correct. Auxin promotes root initiation.
**b) Low auxin : High cytokinin – Incorrect. This ratio favors shoot formation.
**c) Equal ratio – Incorrect. Produces undifferentiated callus.
**d) High gibberellin : Low auxin – Incorrect. GA is not used in root induction.

Q2. Which plant growth regulator combination is antagonistic in regulating seed dormancy?

a) Auxin vs Cytokinin
b) Gibberellin vs ABA
c) Cytokinin vs Ethylene
d) Auxin vs Gibberellin

Answer: b) Gibberellin vs ABA

a) Auxin vs Cytokinin – Incorrect. Mainly linked to apical dominance.
b) Gibberellin vs ABA – Correct. GA breaks dormancy; ABA induces dormancy.
c) Cytokinin vs Ethylene – Incorrect. No direct antagonism in dormancy.
d) Auxin vs Gibberellin – Incorrect. Both stimulate growth.

Q3. Which of the following is used to delay senescence in storage of leafy vegetables?

a) Ethylene
b) ABA
c) Cytokinin
d) Auxin

Answer: c) Cytokinin

a) Ethylene – Incorrect. Promotes senescence.
b) ABA – Incorrect. Stress hormone → promotes senescence.
c) Cytokinin – Correct. Antisenescence hormone, keeps leaves fresh.
d) Auxin – Incorrect. No major role in senescence prevention.

Q4. Which hormone induces flowering in long-day plants under short-day conditions?

a) Gibberellin
b) Auxin
c) Cytokinin
d) Ethylene

Answer: a) Gibberellin

a) Gibberellin – Correct. GA overcomes photoperiodic requirement.
b) Auxin – Incorrect. Not related to photoperiod.
c) Cytokinin – Incorrect. Involved in growth, not flowering.
d) Ethylene – Incorrect. Involved in senescence/ripening.

Q5. Which of the following pairs is correctly matched?

a) IAA – Synthetic auxin
b) NAA – Natural auxin
c) Zeatin – Natural cytokinin
d) GA₃ – Synthetic gibberellin

Answer: c) Zeatin – Natural cytokinin

a) IAA – Incorrect. IAA is natural auxin.
b) NAA – Incorrect. NAA is synthetic auxin.
c) Zeatin – Correct. First discovered natural cytokinin from maize kernels.
d) GA₃ – Incorrect. GA₃ is a natural gibberellin.

Q6. Which plant growth regulator is used to promote sugarcane yield by increasing internode length?

a) Gibberellin
b) Auxin
c) Cytokinin
d) Ethylene

Answer: a) Gibberellin

a) Gibberellin – Correct. Elongates stem, increases sugarcane yield.
b) Auxin – Incorrect. Root initiation, apical dominance.
c) Cytokinin – Incorrect. Promotes cell division, not internode elongation.
d) Ethylene – Incorrect. Shortens internodes.

Q7. Which plant hormone is responsible for abscission of leaves and fruits?

a) Cytokinin
b) ABA
c) Ethylene
d) Gibberellin

Answer: c) Ethylene

a) Cytokinin – Incorrect. Delays senescence, opposite effect.
b) ABA – Incorrect. Induces dormancy but not direct abscission.
c) Ethylene – Correct. Promotes abscission.
d) Gibberellin – Incorrect. Stimulates growth, not abscission.

Q8. Which hormone helps in malting process during brewing industry?

a) Auxin
b) Gibberellin
c) Cytokinin
d) Ethylene

Answer: b) Gibberellin

a) Auxin – Incorrect. Not used in brewing.
b) Gibberellin – Correct. Stimulates hydrolytic enzymes in barley seeds.
c) Cytokinin – Incorrect. Not related to malt formation.
d) Ethylene – Incorrect. Ripening agent, not used in malting.

Q9. Parthenocarpic seedless tomatoes can be produced by spraying:

a) ABA
b) Auxin
c) Gibberellin
d) Both b & c

Answer: d) Both b & c

a) ABA – Incorrect. Causes dormancy, not parthenocarpy.
b) Auxin – Partially correct. Auxin induces parthenocarpy.
c) Gibberellin – Partially correct. GA also induces parthenocarpy.
d) Both b & c – Correct. Either auxin or gibberellin can induce seedless fruit.

Q10. Which hormone increases α-amylase activity in germinating barley seeds?

a) Auxin
b) Cytokinin
c) Gibberellin
d) ABA

Answer: c) Gibberellin

a) Auxin – Incorrect. Not involved.
b) Cytokinin – Incorrect. Division, not enzyme induction.
c) Gibberellin – Correct. Stimulates aleurone layer → α-amylase release.
d) ABA – Incorrect. Inhibits germination.

Q11. Apical dominance is due to higher concentration of:

a) Auxin in apical bud
b) Cytokinin in root tip
c) Gibberellin in lateral buds
d) Ethylene in leaves

Answer: a) Auxin in apical bud

a) Auxin – Correct. Suppresses lateral bud outgrowth.
b) Cytokinin – Incorrect. Promotes lateral bud growth.
c) Gibberellin – Incorrect. Promotes elongation.
d) Ethylene – Incorrect. Promotes senescence, not dominance.

Q12. Application of which hormone can substitute long-day requirement for flowering?

a) Cytokinin
b) Gibberellin
c) Ethylene
d) ABA

Answer: b) Gibberellin

a) Cytokinin – Incorrect. Not related to flowering induction.
b) Gibberellin – Correct. Induces flowering in long-day plants.
c) Ethylene – Incorrect. Mainly senescence and ripening.
d) ABA – Incorrect. Inhibitory hormone.

Q13. Which one is wrongly matched?

a) Auxin – Root initiation
b) Gibberellin – Internode elongation
c) Cytokinin – Chloroplast differentiation
d) ABA – Cell division

Answer: d) ABA – Cell division

a) Auxin – Correct. Induces roots.
b) Gibberellin – Correct. Promotes elongation.
c) Cytokinin – Correct. Promotes chloroplast differentiation.
d) ABA – Incorrect. Inhibits growth, not cell division.

Q14. Which hormone promotes femaleness in cucurbits?

a) Auxin
b) Cytokinin
c) Ethylene
d) Gibberellin

Answer: c) Ethylene

a) Auxin – Incorrect. Not related to sex expression.
b) Cytokinin – Incorrect. Promotes cell division, not sex expression.
c) Ethylene – Correct. Promotes female flowers in cucurbits.
d) Gibberellin – Incorrect. Promotes maleness in cucurbits.

Q15. 2,4-D is used in agriculture mainly as:

a) Rooting hormone
b) Herbicide
c) Anti-senescence hormone
d) Flower-inducing hormone

Answer: b) Herbicide

a) Rooting hormone – Incorrect. IBA/NAA used for rooting.
b) Herbicide – Correct. Selective for dicots.
c) Anti-senescence – Incorrect. Cytokinins delay senescence.
d) Flower-inducing – Incorrect. GA induces flowering.

Q16. Which hormone delays sprouting in potato tubers?

a) Auxin
b) Cytokinin
c) ABA
d) Gibberellin

Answer: c) ABA

a) Auxin – Incorrect. Not related to dormancy.
b) Cytokinin – Incorrect. Promotes sprouting.
c) ABA – Correct. Maintains dormancy in tubers.
d) Gibberellin – Incorrect. Breaks dormancy.

Q17. Which of the following is the main inhibitor of seed germination?

a) Gibberellin
b) Cytokinin
c) ABA
d) Ethylene

Answer: c) ABA

a) Gibberellin – Incorrect. Breaks dormancy, promotes germination.
b) Cytokinin – Incorrect. Promotes cell division, not inhibition.
c) ABA – Correct. Main dormancy hormone.
d) Ethylene – Incorrect. Promotes ripening, not inhibition of germination.

Q18. Which hormone is antagonistic to auxin in apical dominance?

a) Cytokinin
b) ABA
c) Gibberellin
d) Ethylene

Answer: a) Cytokinin

a) Cytokinin – Correct. Promotes lateral bud growth.
b) ABA – Incorrect. Causes dormancy, not antagonism.
c) Gibberellin – Incorrect. Works synergistically with auxin.
d) Ethylene – Incorrect. Not a main antagonist in dominance.

Q19. The hormone used for synchronizing fruit ripening is:

a) Auxin
b) Gibberellin
c) Cytokinin
d) Ethylene

Answer: d) Ethylene

a) Auxin – Incorrect. Not used in ripening.
b) Gibberellin – Incorrect. Used in elongation, not ripening.
c) Cytokinin – Incorrect. Delays senescence, not ripening.
d) Ethylene – Correct. Ripening hormone.

Q20. Which growth regulator induces flowering in pineapples?

a) Cytokinin
b) Ethylene
c) Auxin
d) Gibberellin

Answer: b) Ethylene

a) Cytokinin – Incorrect. Not related to flowering.
b) Ethylene – Correct. Used in pineapple flowering induction.
c) Auxin – Incorrect. Not a flowering hormone.
d) Gibberellin – Incorrect. Used in bolting and flowering in long-day plants.

Q21. Which hormone causes transverse swelling in stems?

a) Ethylene
b) Auxin
c) Gibberellin
d) Cytokinin

Answer: a) Ethylene

a) Ethylene – Correct. Inhibits elongation, promotes lateral swelling.
b) Auxin – Incorrect. Promotes elongation, not swelling.
c) Gibberellin – Incorrect. Stimulates elongation.
d) Cytokinin – Incorrect. Promotes division.

**Q22. Which growth regulator was first identified in Gibberella fujikuroi fungus?**

a) Auxin
b) Gibberellin
c) Cytokinin
d) ABA

Answer: b) Gibberellin

a) Auxin – Incorrect. Discovered in oat coleoptiles.
b) Gibberellin – Correct. From bakanae disease fungus.
c) Cytokinin – Incorrect. Discovered as kinetin in tobacco culture.
d) ABA – Incorrect. Discovered later.

Q23. Which hormone is known as “stress hormone”?

a) Auxin
b) ABA
c) Gibberellin
d) Cytokinin

Answer: b) ABA

a) Auxin – Incorrect. Growth promoter.
b) ABA – Correct. Stress hormone, causes stomatal closure.
c) Gibberellin – Incorrect. Growth promoter.
d) Cytokinin – Incorrect. Growth promoter.

Q24. Which growth regulator is involved in cell wall loosening and acid growth hypothesis?

a) Auxin
b) Cytokinin
c) Gibberellin
d) ABA

Answer: a) Auxin

a) Auxin – Correct. Stimulates proton pump → acidification → cell wall loosening.
b) Cytokinin – Incorrect. Cell division, not elongation.
c) Gibberellin – Incorrect. Works with auxin but not central.
d) ABA – Incorrect. Inhibitor, no elongation.

Q25. Which one of the following promotes seed germination in lettuce under light?

a) Auxin
b) Cytokinin
c) Gibberellin
d) ABA

Answer: c) Gibberellin

a) Auxin – Incorrect. Not involved.
b) Cytokinin – Incorrect. Not linked to germination.
c) Gibberellin – Correct. Light-sensitive lettuce seeds require GA for germination.
d) ABA – Incorrect. Inhibits germination.

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Part 7 – Plant Growth & Development – Complex NEET-Oriented Questions