50. Following are certain facts about the effect of abscisic acid (ABA) on the development and physiological effect of plants:
    A. ABA promotes leaf senescence independent of ethylene
    B. ABA promotes shoot growth and inhibits root growth at low water potential.
    C.ABA inhibits gibberellin induced enzyme production
    D. Seed dormancy is controlled by ratio of ABA and gibberllin

Which one of the following combination of above statements is true?

(1) A, B and C                 (2) B, C and D

(3) A, B and D                  (4) A, C and D

Correct combination: (4) A, C and D

Explanation:

• (A) ABA promotes leaf senescence independent of ethylene signaling, acting as a key hormone in aging and stress responses.

• (B) ABA does not promote shoot growth; instead, it typically inhibits shoot growth, especially under low water potential, while sometimes promoting root growth to enhance water uptake. So, statement B is incorrect.

• (C) ABA inhibits gibberellin-induced enzyme production, such as amylase in seeds, thus delaying germination and growth.

• (D) Seed dormancy is controlled by the balance or ratio between ABA and gibberellins, with ABA promoting dormancy and gibberellins promoting germination.

Option-wise:

• (1) A, B and C — B is incorrect.

• (2) B, C and D — B is incorrect.

• (3) A, B and D — B is incorrect.

• (4) A, C and D — correct combination.

  Abscisic acid plays multifunctional roles, including promoting senescence, regulating seed dormancy via antagonism with gibberellins, and inhibiting enzymes induced by growth-promoting hormones, thereby helping plants adapt to environmental stresses effectively.