Select the pair that consists of plant growth promoters only.

Options

A. Auxins and cytokinins
B. Gibberellins and ABA
C. Ethylene and ABA
D. All of these

Answer

To solve the question of selecting the pair that consists of plant growth promoters only, we will analyze the given options step by step.

### Step-by-Step Solution:

1. **Understand Plant Growth Promoters**:
- Plant growth promoters are substances that enhance the growth and development of plants. Common examples include auxins, cytokinins, gibberellins, and ethylene.

2. **Evaluate the Options**:
- We need to analyze each option provided to identify which ones consist solely of plant growth promoters.

3. **Option 1: Auxin and Cytokinins**:
- **Auxins**: These are known to promote cell enlargement, root and shoot elongation, and secondary growth in plants. They are definitely plant growth promoters.
- **Cytokinins**: These promote cell division, break seed dormancy, and aid in morphogenesis (the differentiation of cells into tissues). They are also recognized as plant growth promoters.
- **Conclusion**: This pair consists of plant growth promoters.

4. **Option 2: Gibberellin and Abscisic Acid**:
- **Gibberellins**: These are plant growth promoters that stimulate stem elongation, seed germination, and flowering.
- **Abscisic Acid (ABA)**: This is primarily a plant growth inhibitor that promotes dormancy and stress responses.
- **Conclusion**: This pair does not consist of plant growth promoters only.

5. **Option 3: Ethylene and Abscisic Acid**:
- **Ethylene**: This is a plant hormone that promotes fruit ripening and can influence growth, but it is not primarily a growth promoter.
- **Abscisic Acid**: As mentioned, this is a growth inhibitor.
- **Conclusion**: This pair does not consist of plant growth promoters only.

6. **Option 4: All of the Above**:
- Since we have already established that not all options consist of plant growth promoters, this option is incorrect.
- **Conclusion**: This pair does not consist of plant growth promoters only.

7. **Final Answer**:
- The correct pair that consists of plant growth promoters only is **Auxin and Cytokinins**.