Question

Match List I with List II :

List I (Growth Regulator)
A. 2,4-D
B. $GA_3$
C. Kinetin
D. ABA

List II (Function/Effect)
I. Brewing industry
II. Stimulation of stomatal closure
III. Herbicide
IV. Nutrient mobilisation

Choose the correct answer from the options given below :

• A. A-IV, B-III, C-II, D-I
• B. A-I, B-II, C-IV, D-III
• C. A-I, B-IV, C-III, D-II
• D. A-III, B-I, C-IV, D-II

Hint:

Remember the "Stress" link: ABA helps plants "close up" during stress. For $GA_3$, think "G" for "Germination" and "Grain" (malting in brewing).

Answer 1

The Correct Option is D

Step 1 : Understanding the Question
The objective of this question is to pair various Plant Growth Regulators (PGRs) with their corresponding physiological effects or commercial uses. Understanding the specific roles of Auxins, Gibberellins, Cytokinins, and Abscisic Acid is essential.
Step 2 : Key Formulas and approach
This is a matching-type question where the approach is to correlate each hormone with its unique biological signature. There are no mathematical equations, but the mapping of "Hormone $\rightarrow$ Physiological Response" serves as the core logic.
Step 3 : Detailed Explanation

2,4-D (A): 2,4-dichlorophenoxyacetic acid is a synthetic auxin. In agriculture, it is primarily used as a selective herbicide (III) to kill broad-leaved dicotyledonous weeds while sparing monocotyledonous cereal crops.

Gibberellic Acid (B): $\text{GA}_3$ is widely used in the brewing industry (I) to accelerate the malting process. It stimulates the production of enzymes like $\alpha$-amylase that break down starch into maltose.

Kinetin (C): This is a cytokinin that promotes nutrient mobilisation (IV), which helps in delaying the aging of leaves, also known as senescence. It ensures nutrients are directed to younger growing parts.

ABA (D): Abscisic acid is known as the "stress hormone." One of its vital roles is the stimulation of stomatal closure (II) during water stress to prevent excessive transpiration and dehydration.

Step 4 : Final Answer
The correct matching is A-III, B-I, C-IV, and D-II. Thus, the correct option is (A).