Which of the following is involved in the symbiotic nitrogen fixation?

Options

A. leghaemoglobin
B. Nitrobacter
C. Nitrosomonas
D. Pseudomonas

Answer

To determine which of the given options is involved in symbiotic nitrogen fixation, let's analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Nitrogen Fixation**:
- Nitrogen fixation is the process of converting atmospheric nitrogen (N₂) into ammonia (NH₃). This is crucial for plants as they cannot utilize atmospheric nitrogen directly.

2. **Types of Nitrogen Fixation**:
- Nitrogen fixation can occur through natural processes (biological) or industrial processes. Symbiotic nitrogen fixation is a biological process that involves a mutual relationship between plants and certain bacteria.

3. **Identifying the Options**:
- The options provided are:
- A. Hemoglobin
- B. Nitrovector
- C. Nitrosomonas
- D. Pseudomonas

4. **Analyzing Each Option**:
- **A. Hemoglobin**: Specifically, leg hemoglobin is a protein found in root nodules of leguminous plants. It helps transport oxygen to the nitrogen-fixing bacteria (like Rhizobium) in the nodules. This is directly related to symbiotic nitrogen fixation.
- **B. Nitrovector**: This is a genus of bacteria that is involved in the conversion of nitrite to nitrate, not directly in nitrogen fixation.
- **C. Nitrosomonas**: This is a free-living bacterium that converts ammonium ions into nitrite, which is part of the nitrification process, not nitrogen fixation.
- **D. Pseudomonas**: This genus includes bacteria that are involved in denitrification, converting nitrates back to nitrogen gas, which is the opposite of nitrogen fixation.

5. **Conclusion**:
- The only option that is directly involved in symbiotic nitrogen fixation is **A. Hemoglobin** (specifically leg hemoglobin), as it plays a crucial role in the relationship between leguminous plants and nitrogen-fixing bacteria.

### Final Answer:
**A. Hemoglobin**

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