Anabaena and Azolla have a mutualistic relationship. Mutualism is a type of symbiotic relationship where both organisms benefit from each other.

Mutualism between Anabaena and Azolla:

Introduction:
- Anabaena is a type of cyanobacteria that is capable of nitrogen fixation.
- Azolla is a small aquatic fern that forms a symbiotic relationship with Anabaena.

Key Points:

1. Nitrogen Fixation:
- Anabaena has specialized cells called heterocysts that can fix atmospheric nitrogen into a usable form.
- Azolla lacks the ability to fix nitrogen on its own.
- Azolla provides a suitable environment for Anabaena to grow and carry out nitrogen fixation.

2. Nitrogen Source:
- Anabaena supplies fixed nitrogen to Azolla, which is essential for its growth and development.
- The fixed nitrogen is released by Anabaena and is absorbed by Azolla through its roots.

3. Growth Promotion:
- The fixed nitrogen provided by Anabaena stimulates the growth of Azolla.
- Azolla grows rapidly in the presence of Anabaena, forming a dense mat on the water surface.

4. Nutrient Recycling:
- Azolla absorbs nutrients from the water, preventing their loss from the ecosystem.
- When Azolla dies and decomposes, the nutrients are released back into the water, making them available for other organisms.

5. Habitat and Protection:
- Azolla provides a protected habitat for Anabaena by forming a mat on the water surface.
- This mat shields Anabaena from excessive sunlight, desiccation, and predation.

Conclusion:
The mutualistic relationship between Anabaena and Azolla is beneficial for both organisms. Anabaena provides fixed nitrogen to Azolla, promoting its growth, while Azolla provides a suitable habitat and protection for Anabaena. This symbiotic interaction plays an important role in nutrient cycling and ecosystem functioning.