Which one is not a growth promoter ?

Options

A. ABA
B. GA
C. IAA
D. CK.

Answer

To determine which substance is not a growth promoter, we can analyze the given options based on their roles in plant growth regulation.

### Step-by-Step Solution:

1. **Identify the Substances**: The options provided are:
- Abscisic Acid (ABA)
- Gibberellic Acid (GA)
- Indole-3-Acetic Acid (IAA)
- Cytokinin

2. **Understand Growth Promoters**: Growth promoters are substances that stimulate plant growth. Common plant hormones that act as growth promoters include:
- **Gibberellic Acid (GA)**: Promotes stem elongation, seed germination, and flowering.
- **Indole-3-Acetic Acid (IAA)**: A type of auxin that promotes cell elongation and is involved in various growth processes.
- **Cytokinin**: Promotes cell division and growth, particularly in shoots and roots.

3. **Identify the Growth Inhibitor**:
- **Abscisic Acid (ABA)**: This hormone is known to inhibit growth and is involved in stress responses, such as closing stomata during drought conditions.

4. **Conclusion**: Since ABA (Abscisic Acid) is known to inhibit growth rather than promote it, it is the correct answer to the question.

### Final Answer:
**Abscisic Acid (ABA) is not a growth promoter.**

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