Question

Antagonist of Gibberellin Hormone -

• A. Auxin
• B. Cytokinin
• C. Abscisic Acid (ABA)
• D. Ethylene

Hint:

Gibberellins promote seed germination, whereas ABA promotes seed dormancy. This opposite action makes ABA the antagonist of gibberellins.

Answer 1

The Correct Option is C

Concept: Plant growth regulators coordinate growth, development, dormancy, flowering, and fruit formation. Some hormones promote growth while others inhibit growth. Abscisic acid is generally regarded as a growth-inhibiting hormone and often acts antagonistically to gibberellins.

Step 1: Understand the role of gibberellins. Gibberellins promote:
• Stem elongation
• Seed germination
• Breaking of dormancy
• Flowering in some plants Thus, gibberellins are growth-promoting hormones.

Step 2: Understand the role of ABA. Abscisic acid promotes:
• Seed dormancy
• Bud dormancy
• Stomatal closure
• Growth inhibition These effects are generally opposite to those of gibberellins.

Step 3: Identify the antagonist. Since ABA opposes many actions of gibberellins, it is regarded as their physiological antagonist. \[ \boxed{\text{ABA}} \] Hence, the correct answer is \[ \boxed{(C)\ \text{Abscisic Acid}} \]