Which of following microbe is most active nitrogenj fixer in rice field in India?

Options

A. Rhizobium
B. Rhodospirillum
C. Frankia
D. Aulosira

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the most active nitrogen fixer in rice fields in India. Nitrogen fixation is a crucial process where certain microbes convert atmospheric nitrogen into a form that plants can use.

2. **Identifying the Options**: The options given are:
- A) Rhizobium
- B) Rhodospirillum
- C) Francia
- D) Allocera

3. **Reviewing Each Microbe**:
- **Rhizobium**: This is a well-known nitrogen-fixing bacterium that forms symbiotic relationships with legumes.
- **Rhodospirillum**: This is a genus of purple non-sulfur bacteria that can fix nitrogen but is not primarily associated with rice fields.
- **Francia**: This is less commonly known and is not the primary nitrogen fixer in rice fields.
- **Allocera**: Specifically, *Allocera fertilissima* is a blue-green algae (also known as cyanobacteria) that is known for its high nitrogen-fixing activity.

4. **Determining the Most Active Nitrogen Fixer**: Among the options, *Allocera fertilissima* is recognized as the most active nitrogen fixer in rice fields in India due to its ability to add both organic matter and nitrogen to the soil.

5. **Conclusion**: The correct answer to the question is **D) Allocera**.

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