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

Answer

To solve the question regarding which statement is not correct about the process of symbiotic nitrogen fixation in leguminous plants, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Understanding Symbiotic Nitrogen Fixation**:
- Leguminous plants have a symbiotic relationship with nitrogen-fixing bacteria, such as Rhizobium. These bacteria live in root nodules and convert atmospheric nitrogen (N₂) into ammonia (NH₃), which plants can use.

2. **Analyzing Each Statement**:
- **Statement A**: "Leghemoglobin scavenges oxygen and is pinkish in color."
- This statement is **correct**. Leghemoglobin is a pigment found in root nodules that helps transport oxygen to the nitrogen-fixing bacteria while preventing excess oxygen from denaturing the nitrogenase enzyme.

- **Statement B**: "Nodules act as sites for nitrogen fixation."
- This statement is also **correct**. The root nodules of leguminous plants are indeed the sites where nitrogen fixation occurs, as they house the nitrogen-fixing bacteria.

- **Statement C**: "Enzyme nitrogenase catalyzes the conversion of atmospheric nitrogen to ammonia."
- This statement is **correct**. The enzyme nitrogenase is responsible for the reduction of atmospheric nitrogen to ammonia, which is a crucial step in nitrogen fixation.

- **Statement D**: "Nitrogenase is insensitive to oxygen."
- This statement is **incorrect**. Nitrogenase is actually very sensitive to oxygen; it denatures in the presence of oxygen, which is why leghemoglobin is important to maintain low oxygen levels in the nodules.

3. **Conclusion**:
- The statement that is not correct regarding the process of nitrogen fixation in leguminous plants is **Statement D**: "Nitrogenase is insensitive to oxygen."

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

---