What is required for nitrogen fixation by Rhizobium

Options

A. Potassium
B. Phosphorus
C. Nitrate
D. Sodium

Explanation

To answer the question "What is required for nitrogen fixation by Rhizobium?", we can break down the solution into several steps:

### Step-by-Step Solution:

1. **Understand Nitrogen Fixation**: Nitrogen fixation is the process by which atmospheric nitrogen (N₂) is converted into ammonia (NH₃), a form that plants can use.

2. **Identify the Role of Rhizobium**: Rhizobium is a type of nitrogen-fixing bacteria that forms a symbiotic relationship with leguminous plants (like peas and beans). They reside in the root nodules of these plants.

3. **Determine Nutrient Requirements**: For Rhizobium to effectively fix nitrogen, certain nutrients are necessary. Among the options provided (potassium, phosphorus, nitrate, and sodium), we need to identify which one is essential.

4. **Focus on Phosphorus**: Phosphorus is crucial for the growth and functioning of Rhizobium. It plays a significant role in energy transfer and is vital for the synthesis of nucleic acids and ATP, which are important for the nitrogen fixation process.

5. **Conclusion**: Therefore, phosphorus is required for nitrogen fixation by Rhizobium, enhancing the symbiotic relationship with legume crops and facilitating the conversion of atmospheric nitrogen into a usable form for plants.

### Final Answer:
Phosphorus is required for nitrogen fixation by Rhizobium.

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