Most active nitrogen fixing blue-green alga of rice fields is

Options

A. Anabaena azollae
B. Aulosira fertilissima
C. Cylindrospermum licheniforme
D. Nostoc cycadacearum

Answer

**Step-by-Step Solution:**

1. **Understanding Nitrogen Fixation**:
- Nitrogen fixation is the process by which atmospheric nitrogen (N₂) is converted into a form that plants can use, such as ammonia (NH₃). This process is crucial for plant growth as nitrogen is an essential nutrient.

2. **Identifying Nitrogen-Fixing Organisms**:
- There are two main types of nitrogen-fixing organisms:
- **Cyanobacteria** (also known as blue-green algae) which are autotrophic and can fix nitrogen independently.
- **Symbiotic bacteria** which live in association with plants (e.g., legumes).

3. **Focusing on Cyanobacteria**:
- Cyanobacteria are important in agriculture, particularly in rice fields, where they can enhance soil fertility by fixing atmospheric nitrogen.

4. **Evaluating the Options**:
- The question provides four options for the most active nitrogen-fixing blue-green alga in rice fields:
1. Anabena Azula
2. Allocera Fertilisma
3. Cylindrospermum Lycanford
4. Nostoccyclic Serum

5. **Analyzing Each Option**:
- **Anabena Azula**: While it is a cyanobacterium, it is not specifically known for its activity in rice fields.
- **Allocera Fertilisma**: This is recognized as the most active non-symbiotic nitrogen-fixing blue-green alga in rice fields, making it a strong candidate.
- **Cylindrospermum Lycanford**: This organism does not significantly contribute to nitrogen fixation in rice fields.
- **Nostoccyclic Serum**: Similar to the previous option, it is not known for its nitrogen-fixing capabilities in rice fields.

6. **Conclusion**:
- Based on the analysis, the correct answer is **Allocera Fertilisma**, as it is the most active nitrogen-fixing blue-green alga in rice fields.

**Final Answer**: Allocera Fertilisma

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