Which of the following is a symbiotic nitrogen fixer ?

Options

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

Answer

**Step-by-Step Solution:**

1. **Understanding Symbiotic Nitrogen Fixation**:
- Symbiotic nitrogen fixation refers to the process where certain plants and bacteria live together in a mutually beneficial relationship. The bacteria convert atmospheric nitrogen into ammonia, which the plants can use, while the plants provide carbohydrates and other nutrients to the bacteria.

2. **Identifying the Options**:
- The options given are Azola, Glomus, Azotobacter, and Frankia. We need to determine which of these is known for forming a symbiotic relationship for nitrogen fixation.

3. **Analyzing Each Option**:
- **Azola**: This is a water fern that forms a symbiotic relationship with the cyanobacterium Anabaena. In this relationship, Anabaena fixes nitrogen, which is then used by Azola, while Azola provides nutrients to Anabaena.
- **Glomus**: This is a genus of fungi that forms mycorrhizal associations with plants, but it does not fix nitrogen.
- **Azotobacter**: This is a free-living nitrogen-fixing bacterium that does not form symbiotic relationships with plants.
- **Frankia**: This is a genus of nitrogen-fixing bacteria that can form symbiotic relationships with certain plants (like alder trees), but it is not associated with Azola.

4. **Conclusion**:
- Based on the analysis, Azola is the correct answer as it forms a symbiotic relationship with Anabaena, which is a nitrogen-fixing cyanobacterium.

5. **Final Answer**:
- The symbiotic nitrogen fixer among the options is **Azola**.

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