Which of the following PGR shows dual role, growth promotion and growth inhibition:

Options

A. Cytokinin
B. Gibberellins
C. Ethylene
D. Abscisic acid

Answer

To solve the question regarding which plant growth regulator (PGR) shows a dual role of growth promotion and growth inhibition, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of PGR**:
- Plant Growth Regulators (PGRs) are substances that influence the growth and development of plants. They can promote growth, inhibit growth, or have both effects.

2. **Identify the Options**:
- The question provides four options (not listed here), and we need to evaluate each one to determine if it exhibits dual roles.

3. **Evaluate Cytokinins**:
- Cytokinins are known for promoting cell division and growth. They primarily act as growth promoters and do not inhibit growth.
- **Conclusion**: Cytokinins do not show dual roles.

4. **Evaluate Gibberellins**:
- Gibberellins are involved in promoting growth, particularly in seed germination and stem elongation. They do not have a growth-inhibiting effect.
- **Conclusion**: Gibberellins do not show dual roles.

5. **Evaluate Ethylene**:
- Ethylene is unique as it can promote growth (e.g., through internodal elongation) and also inhibit growth during certain processes like senescence (the aging process of plants).
- **Conclusion**: Ethylene shows dual roles of both promoting and inhibiting growth.

6. **Evaluate Abscisic Acid**:
- Abscisic acid primarily acts as a growth inhibitor, especially during stress conditions (like drought) and does not promote growth.
- **Conclusion**: Abscisic acid does not show dual roles.

7. **Final Answer**:
- Based on the evaluations, the only PGR that shows both growth promotion and growth inhibition is **Ethylene**.

### Answer:
**C. Ethylene**

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