Which is the most crucial enzyme found in root nodules for Na fixation?

Explanation

**Step-by-Step Solution:**

1. **Identify the Context**: The question asks for the most crucial enzyme involved in nitrogen fixation found in root nodules.

2. **Recognize the Enzyme**: The enzyme responsible for nitrogen fixation in root nodules is known as nitrogenase.

3. **Understand the Function**: Nitrogenase is crucial because it facilitates the conversion of atmospheric nitrogen (N₂) into ammonia (NH₃), which can be utilized by plants.

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