Leguminous plants are able to fix atmospheric nitrogen through the process of symbiotic nitrogen fixation. Which one of the following statements is not correct for this process of nitrogen fixation ?

Options

A. Leghaemoglobin scavenges oxygen and is pinkish in colour
B. Nodules acts as sites for nitrogen fixation
C. The enzyme nitrogenase catalyses the conversion of atmospheric `N_(2)` to `NH_(3)`
D. Nitrogenase is insensitive to oxygen

Answer

To solve the question regarding the incorrect statement about the process of symbiotic nitrogen fixation in leguminous plants, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Process of Nitrogen Fixation**:
- Leguminous plants can fix atmospheric nitrogen through a symbiotic relationship with nitrogen-fixing bacteria (like Rhizobium) that reside in root nodules.

2. **Identify Key Components**:
- The enzyme responsible for nitrogen fixation is called nitrogenase. This enzyme converts atmospheric nitrogen (N2) into ammonia (NH3).
- Nitrogenase requires energy and operates best under anaerobic conditions (absence of oxygen).

3. **Role of Leghemoglobin**:
- Leghemoglobin is a pigment found in the root nodules of leguminous plants. It serves to maintain anaerobic conditions by scavenging oxygen, thus protecting the nitrogenase enzyme from being inhibited by oxygen.

4. **Evaluate the Statements**:
- **Statement 1**: "Leghemoglobin scavenges oxygen and is pink in color." - This is true.
- **Statement 2**: "Nodules act as sites for nitrogen fixation." - This is also true.
- **Statement 3**: "The enzyme nitrogenase catalyzes the conversion of atmospheric N2 to ammonia." - This is true as well.
- **Statement 4**: "Nitrogenase is insensitive to oxygen." - This is false because nitrogenase is sensitive to oxygen and requires anaerobic conditions for optimal activity.

5. **Conclusion**:
- The statement that is not correct regarding the process of nitrogen fixation is: "Nitrogenase is insensitive to oxygen."

### Final Answer:
The incorrect statement is: "Nitrogenase is insensitive to oxygen."

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