Which of the following growth regulators can fit either of the groups (promoter and inhibitor) –

Options

A. `C_2 H_4`
B. `ABA`
C. `GA`
D. `IA A`

Answer

To determine which growth regulator can fit into either the promoter or inhibitor category, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Plant Growth Regulators**:
- Plant growth regulators (PGRs) are substances that influence plant growth and development. They can be classified into two main categories: promoters and inhibitors.

2. **Identify Plant Growth Promoters**:
- Promoters are substances that enhance plant growth. They are involved in processes such as cell division, cell enlargement, flowering, and fruiting.
- Examples of plant growth promoters include auxins, gibberellins, and cytokinins.

3. **Identify Plant Growth Inhibitors**:
- Inhibitors are substances that suppress or inhibit plant growth. They often come into play during stress conditions or dormancy.
- Examples of plant growth inhibitors include abscisic acid and ethylene.

4. **Analyze Ethylene**:
- Ethylene is a gaseous plant hormone that can act as both a promoter and an inhibitor.
- It promotes fruit ripening and can enhance certain growth processes, but it also plays a role in inhibiting growth under stress conditions and can induce senescence.

5. **Conclusion**:
- Since ethylene can function in both capacities (as a growth promoter and as a growth inhibitor), it fits into either group. Therefore, the correct answer to the question is ethylene.

### Final Answer:
- The growth regulator that can fit into either the promoter or inhibitor category is **ethylene (C2H4)**.