Which one of the following is a natural growth inhibitor ?

Options

A. NAA
B. ABA
C. GA
D. Auxin

Answer

To determine which of the given options is a natural growth inhibitor, we need to analyze each option based on their characteristics as plant hormones.

### Step-by-Step Solution:

1. **Understand the Question**: The question asks for a natural growth inhibitor among the given options: NAA, ABA, GA, and auxin.

2. **Identify the Options**:
- **Option A: NAA (Naphthalene Acetic Acid)**: This is a synthetic plant hormone used primarily as a rooting agent. It promotes growth rather than inhibiting it.
- **Option B: ABA (Abscisic Acid)**: This is a natural plant hormone known as a growth inhibitor. It plays a crucial role in stress responses and helps in the regulation of plant growth.
- **Option C: GA (Gibberellins)**: These are natural plant hormones that promote growth, particularly in stem elongation and seed germination.
- **Option D: Auxin**: Auxins are also natural plant hormones that promote growth, especially in cell elongation and root formation.

3. **Analyze Each Option**:
- NAA is synthetic and promotes growth.
- ABA is natural and inhibits growth.
- GA promotes growth.
- Auxin promotes growth.

4. **Conclusion**: Based on the analysis, the only natural growth inhibitor among the options is **ABA (Abscisic Acid)**.

5. **Final Answer**: The correct answer is **Option B: ABA (Abscisic Acid)**.