Roots of Trifolium alexandrinum contains nitrogen fixing

Options

A. Rhizobium
B. Nostoc
C. Aerorhizobium
D. Anabaena.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the nitrogen-fixing organisms present in the roots of Trifolium alexandrinum.

2. **Identifying the Options**: The options provided are Rhizobium, Nostoc, Aerorhizobium, and Anabaena.

3. **Researching Each Option**:
- **Rhizobium**: This is a well-known nitrogen-fixing bacterium that forms symbiotic relationships with legumes, but it is not typically associated with Trifolium alexandrinum.
- **Nostoc**: This is a genus of filamentous cyanobacteria known for its ability to fix atmospheric nitrogen. It can be found in both terrestrial and aquatic environments and is known to associate with various plants, including some legumes.
- **Aerorhizobium**: This is less commonly known and does not have a strong association with Trifolium alexandrinum.
- **Anabaena**: Another genus of nitrogen-fixing cyanobacteria, but it is more commonly associated with aquatic environments and certain plants.

4. **Conclusion**: Based on the information, Nostoc is the correct answer as it is known to be present in the roots of Trifolium alexandrinum and is capable of fixing atmospheric nitrogen.

5. **Final Answer**: The roots of Trifolium alexandrinum contain nitrogen-fixing Nostoc.

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