Why is Azolla frequently grown with the rice crop?

Explanation

### Step-by-Step Solution:

1. **Understanding Azolla**: Azolla is a floating pteridophyte, which means it is a type of fern that grows on water surfaces. It is classified as a vascular plant, which means it has specialized tissues for transporting water and nutrients.

**Hint**: Remember that Azolla is not just any plant; it is a specific type of fern that thrives in aquatic environments.

2. **Nitrogen Fixation**: Azolla hosts a symbiotic relationship with a nitrogen-fixing cyanobacterium called Anabaena. This means that Azolla can convert atmospheric nitrogen, which is not usable by plants, into a form that plants can absorb and utilize.

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