The process of `N_(2)` fixation in root nodules is controlled by

Options

A. nif
B. NAA
C. IAA
D. ABA

Answer

### Step-by-Step Solution:

1. **Understanding Nitrogen Fixation**:
- Nitrogen fixation is the process by which atmospheric nitrogen (N₂) is converted into a form that plants can use. This is essential because while nitrogen is abundant in the atmosphere, most plants cannot directly utilize it.

2. **Role of Bacteria**:
- Certain bacteria, particularly those associated with the roots of leguminous plants, play a crucial role in nitrogen fixation. These bacteria form symbiotic relationships with the plants, residing in root nodules.

3. **Symbiotic Relationship**:
- In this relationship, the plant provides the bacteria with carbohydrates and a suitable environment (shelter) in the root nodules, while the bacteria convert atmospheric nitrogen into ammonia, which the plant can use for growth.

4. **Genetic Control**:
- The process of nitrogen fixation in these bacteria is controlled by specific genes. The key gene responsible for this function is known as the NIF gene.

5. **Conclusion**:
- Therefore, the process of N₂ fixation in root nodules is controlled by the NIF gene present in the nitrogen-fixing bacteria.

### Final Answer:
The process of N₂ fixation in root nodules is controlled by the NIF gene.

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