250+ TOP MCQs on Growth Regulators in Plants and Answers

Botany Viva Questions and Answers on “Growth Regulators in Plants – 2”.

1. Which of the following is a gaseous hormone?
a) Ethylene
b) ABA
c) GA
d) Auxin
Answer: a
Clarification: Ethylene is a volatile gaseous hormone. GA, ABA and Auxin are acidic in nature. GA and Auxin are growth promoters while ABA is a growth inhibitor.

2. ABA is a derivative of adenine purine.
a) True
b) False
Answer: b
Clarification: ABA is a growth inhibitor. It is a derivative of carotenoids. It is functional mainly during stressful conditions. Cytokinin is a growth promoter. It is an adenine derivative (N6-furfurylamino purine). It is responsible for plant growth along with auxin hormone.

3. The hormone responsible for femaleness in cucumbers is ________
a) IAA
b) ABA
c) GA
d) Ethylene
Answer: d
Clarification: Ethylene is the hormone responsible for femaleness in cucumbers. IAA and GA induce parthenocarpy in fruits. ABA is not related to ripening of fruits.

4. Richmond Lang effect is linked to ________
a) Cytokinins
b) ABA
c) GA
d) NAA
Answer: a
Clarification: Richmond Lang effect is related to delay in senescence of mature parts of plants. It is linked to cytokinin hormone. GA and NAA also help in attaining precocious maturity. ABA promotes senescence in stressful conditions.

5. The hormone antagonistic to ABA is_______
a) IAA
b) Ethylene
c) GA
d) Kinetin
Answer: c
Clarification: GA acts antagonistically to ABA. IAA is synthetic auxin. Kinetin delays senescence. Ethylene promotes abscission of older parts.

6. The source of hormone ethylene is________
a) oats
b) ethephon
c) coconut milk
d) urine
Answer: b
Clarification: The source of hormone ethylene is ethephon. Source of auxin is oats. Source of cytokinin is coconut kernel. Auxin was first isolated from human urine.

7. The role of PGRs is a kind of intrinsic control.
a) True
b) False
Answer: a
Clarification: Plant growth is controlled by factors categorized into intrinsic control, genomic control and extrinsic control. Plant growth regulators including both promoters and inhibitors are controlled by hormones and come under intrinsic control. All the environmental factors come under extrinsic control.

8. Which of the following hormone is a stress hormone?
a) Ethylene
b) ABA
c) Auxin
d) GA
Answer: b
Clarification: ABA is a hormone which works in stressful conditions. GA acts antagonistic to ABA. Auxin leads to apical dominance. Ethylene is related to early ripening of fruits.

9. Which of the following hormone is used to induce morphogenesis in plant tissue culture?
a) Cytokinins
b) Ethylene
c) Auxin
d) ABA
Answer: a
Clarification: Cytokinins is used to induce morphogenesis in plant tissue culture. Auxin and cytokinin together in varied amounts carry out root and shoot differentiation. Ethylene leads to early ripening. ABA acts as a stress hormone.

10. The hormone responsible for enhancement of the respiration rate of fruits thereby leading to its early ripening is ________
a) Auxin
b) GA₃
c) Ethylene
d) ABA
Answer: c
Clarification: Ethylene is the hormone responsible for enhancement of the respiration rate of fruits thereby leading to its early ripening. Auxin and GA₃ induces parthenocarpy of fruits. ABA acts as a stress hormone.

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