Azolla is used as biofertilizer because

Options

A. its leaves contain nitrogen fixing cyanobacterium Anabaena
B. its leaves are rich in urea
C. it stimulates growth of seedlings of Rice
D. It activates embryo for quick germination

Answer

**Step-by-Step Solution:**

1. **Understanding Azolla**: Azolla is a type of aquatic fern that is often found in rice paddies and is known for its symbiotic relationship with cyanobacteria.

2. **Cyanobacteria Association**: The specific cyanobacteria associated with Azolla is called Anabaena. This cyanobacterium is located in the leaves of Azolla.

3. **Role of Anabaena**: Anabaena is known for its ability to fix atmospheric nitrogen. This means it can convert nitrogen gas from the atmosphere into a form that can be used by plants.

4. **Biofertilizer Function**: Because Azolla contains Anabaena, it acts as a biofertilizer by enriching the soil with nitrogen, which is essential for plant growth, particularly for crops like rice.

5. **Evaluating Options**:
- **Option 1**: "Its leaves contain nitrogen-fixing cyanobacteria Anabaena" - This is correct.
- **Option 2**: "Its leaves are rich in urea" - This is incorrect; Azolla does not primarily provide urea.
- **Option 3**: "It stimulates growth of seedlings of rice" - While it may have some positive effects, this is not the primary reason it is used as a biofertilizer.
- **Option 4**: "It activates embryo for quick germination" - This is also incorrect; the main function is nitrogen fixation.

6. **Conclusion**: The correct reason Azolla is used as a biofertilizer is that its leaves contain nitrogen-fixing cyanobacteria, specifically Anabaena.

**Final Answer**: Azolla is used as a biofertilizer because its leaves contain nitrogen-fixing cyanobacteria Anabaena.

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