40. Which of the following is the plant hormone involved in seed and bud dormancy and in response of plants to stress?

(1) Abscisic acid              (2) Cytokinin
(3) Auxins                      (4) Gibberellins

Correct answer: (1) Abscisic acid

Explanation:

• Abscisic acid (ABA) is the primary plant hormone responsible for seed and bud dormancy and plays a critical role in helping plants respond to various stresses such as drought and salinity.

• ABA functions to inhibit seed germination and maintain dormancy until favorable conditions arise.

• Cytokinins promote cell division and can break dormancy but are not responsible for inducing it.

• Auxins regulate growth and development, not dormancy induction.

• Gibberellins generally promote growth and help break seed dormancy rather than inducing it.

Option-wise:

• (1) Abscisic acid — correct; promotes dormancy and stress tolerance.

• (2) Cytokinin — promotes growth, may break dormancy.

• (3) Auxin — growth regulator, not dormancy hormone.

• (4) Gibberellins — break dormancy, promote germination.

  Abscisic acid is called the “stress hormone” because of its role in maintaining dormancy during unfavorable conditions and helping plants adapt to environmental stresses. It counterbalances growth-promoting hormones like gibberellins to regulate plant development effectively.