Nitrogen fixing enzyme in root nodule is

Options

A. nitrase
B. nitrogenase
C. nitrosomonas
D. nitrogen esterase

Answer

### Step-by-Step Solution:

1. **Understanding Nitrogen Fixation**:
- Nitrogen fixation is the process where atmospheric nitrogen (N₂) is converted into ammonia (NH₃), which plants can utilize for growth and development.

2. **Role of Enzymes in Nitrogen Fixation**:
- Enzymes are biological catalysts that facilitate biochemical reactions. In the case of nitrogen fixation, specific enzymes are involved in converting nitrogen gas into ammonia.

3. **Identifying the Location of Nitrogen Fixation**:
- Nitrogen fixation primarily occurs in the root nodules of leguminous plants. These nodules house symbiotic bacteria that assist in the nitrogen fixation process.

4. **Identifying the Key Enzyme**:
- The key enzyme responsible for nitrogen fixation in the root nodules is **nitrogenase**. This enzyme catalyzes the reaction that converts atmospheric nitrogen into ammonia.

5. **Evaluating the Options**:
- Option A: Nitrase - Incorrect, as this enzyme is not involved in nitrogen fixation.
- Option B: Nitrogenase - Correct, as it is the enzyme that fixes nitrogen in root nodules.
- Option C: Nitrosomonas - Incorrect, as this refers to a genus of bacteria involved in nitrification, not nitrogen fixation.
- Option D: Nitrogen esterase - Incorrect, as this enzyme does not play a role in nitrogen fixation.

6. **Conclusion**:
- The correct answer to the question "Nitrogen fixing enzyme in root nodule is" is **Option B: Nitrogenase**.