choose correct pairs of PGRs showing antagonistic effects.
(A) ABA and GAs for seed germination
(B) ABA and GAs for stomatal closure
(C) Auxin and cytokinin for apical dominance

Options

A. (A), (C) and (D)
B. (B), (C) and (D)
C. (C) and (D) only
D. (B) and (D) only

Answer

To solve the question regarding the correct pairs of plant growth regulators (PGRs) showing antagonistic effects, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Antagonistic Effects**:
- Antagonistic effects refer to the interaction between two substances where one substance counteracts or inhibits the effects of the other. In the context of plant growth regulators, we need to identify pairs that have opposing functions.

2. **Analyzing Option (A)**: **ABA and GAs for seed germination**:
- **ABA (Abscisic Acid)**: This hormone inhibits seed germination and promotes dormancy.
- **GAs (Gibberellic Acid)**: This hormone promotes seed germination and growth.
- **Conclusion**: Since ABA inhibits germination while GAs promote it, this pair shows antagonistic effects. **(Correct)**

3. **Analyzing Option (B)**: **ABA and GAs for stomatal closure**:
- **ABA**: It is known to promote stomatal closure, helping the plant conserve water.
- **GAs**: They do not play a significant role in stomatal closure.
- **Conclusion**: Since only ABA is involved in stomatal closure and GAs do not counteract this effect, this pair does not show antagonistic effects. **(Incorrect)**

4. **Analyzing Option (C)**: **Auxin and cytokinin for apical dominance**:
- **Auxin**: Promotes apical dominance by encouraging the growth of the upper bud.
- **Cytokinins**: Promote lateral bud growth and cell division, which can counteract apical dominance.
- **Conclusion**: Since auxin promotes apical dominance while cytokinins promote lateral growth, they exhibit antagonistic effects. **(Correct)**

5. **Analyzing Option (D)**: **Auxin and ABA for senescence**:
- **Auxin**: Generally delays senescence (aging) in plants.
- **ABA**: Promotes senescence and stress responses.
- **Conclusion**: Since auxin works to delay senescence while ABA promotes it, they show antagonistic effects. **(Correct)**

### Final Answer:
The correct pairs of PGRs showing antagonistic effects are:
- (A) ABA and GAs for seed germination
- (C) Auxin and cytokinin for apical dominance
- (D) Auxin and ABA for senescence