Which of the following is a symbiotic nitrogen fixer ?

Options

A. Azotobacter
B. Frankia
C. Azolla
D. Glomus

Answer

To determine which of the following is a symbiotic nitrogen fixer, we need to analyze each option provided:

1. **Understanding Symbiotic Nitrogen Fixation**:
- Symbiotic nitrogen fixation occurs when certain plants form a mutualistic relationship with nitrogen-fixing bacteria. These bacteria live within the plant tissues and help convert atmospheric nitrogen into a form that the plant can use for growth.

2. **Analyzing the Options**:
- **Azotobacter**: This is a free-living nitrogen-fixing bacterium. It does not form a symbiotic relationship with plants, so it is not the correct answer.
- **Francia**: This bacterium is known to form a symbiotic relationship with non-leguminous plants. It is involved in nitrogen fixation, making it a suitable candidate for the answer.
- **Azolla**: This is a water fern that has a symbiotic relationship with cyanobacteria (Anabaena) for nitrogen fixation. However, Azolla itself is not a nitrogen-fixing organism; rather, it hosts the bacteria that do the fixing.
- **Glomus**: This is a genus of arbuscular mycorrhizal fungi that forms symbiotic relationships with plant roots. While it aids in nutrient uptake, it does not fix nitrogen.

3. **Conclusion**:
- Among the options, **Francia** is the only organism that is a symbiotic nitrogen fixer. It forms a direct association with plants to facilitate nitrogen fixation.

**Final Answer**: The correct answer is **Francia**.

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