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
(D) Auxin and ABA for senescences

Options

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

Answer

To solve the question, we need to identify the correct pairs of plant growth regulators (PGRs) that exhibit antagonistic effects, meaning their actions oppose each other. Let's analyze each option step by step.

### Step 1: Analyze Option A - ABA and GAs for Seed Germination
- **Abscisic Acid (ABA)**: Promotes seed dormancy, preventing germination.
- **Gibberellins (GAs)**: Promote seed germination.
- **Conclusion**: Since ABA inhibits germination while GAs promote it, this pair shows antagonistic effects.

**Hint**: Remember that ABA is associated with dormancy, while GAs are linked to germination.

### Step 2: Analyze Option B - ABA and GAs for Stomatal Closure
- **Abscisic Acid (ABA)**: Causes stomatal closure, reducing water loss during stress.
- **Gibberellins (GAs)**: Generally promote stomatal opening.
- **Conclusion**: ABA and GAs have opposing effects on stomatal behavior, making this pair antagonistic.

**Hint**: Focus on how ABA conserves water by closing stomata, while GAs encourage opening.

### Step 3: Analyze Option C - Auxin and Cytokinin for Apical Dominance
- **Auxin**: Promotes apical dominance by enhancing the growth of the main shoot and inhibiting lateral bud growth.
- **Cytokinin**: Counteracts apical dominance by promoting lateral bud growth.
- **Conclusion**: Auxin and cytokinin have opposing effects on apical dominance, confirming this pair as antagonistic.

**Hint**: Recall that auxin supports the main shoot, while cytokinin encourages side shoots.

### Step 4: Analyze Option D - Auxin and ABA for Senescence
- **Auxin**: Involved in cell growth and elongation, not directly related to senescence.
- **Abscisic Acid (ABA)**: Promotes senescence, which is the aging process in plants.
- **Conclusion**: Since auxin does not promote senescence, this pair does not show antagonistic effects.

**Hint**: Consider that auxin is more about growth, while ABA is linked to aging.

### Final Conclusion
The correct pairs of PGRs showing antagonistic effects are:
- **Option A**: ABA and GAs for seed germination.
- **Option B**: ABA and GAs for stomatal closure.
- **Option C**: Auxin and cytokinin for apical dominance.

Thus, the correct answer is **A, B, and C**.