Which element activates the enzyme nitrate reductase during the nitrogen fixation?

Options

A. molybdenum
B. boron
C. copper
D. zinc

Answer

To determine which element activates the enzyme nitrate reductase during nitrogen fixation, follow these steps:

### Step-by-Step Solution:

1. **Understand Nitrogen Fixation**:
- Nitrogen fixation is the process of converting atmospheric nitrogen (N₂) into a form that plants can use, such as ammonia (NH₃). This process is crucial for plant growth as nitrogen is an essential nutrient.

2. **Identify the Role of Enzymes**:
- During nitrogen fixation, various enzymes are involved, one of which is nitrate reductase. This enzyme plays a key role in the reduction of nitrate to nitrite and then to ammonia.

3. **List the Elements Given**:
- The options provided are:
- A) Molybdenum
- B) Boron
- C) Copper
- D) Zinc

4. **Analyze Each Element's Role**:
- **Molybdenum**: Known to be essential for the activation of nitrate reductase. It forms a complex that is crucial for the enzyme's function.
- **Boron**: Does not play a role in nitrogen fixation and can even be harmful to plants.
- **Copper**: While it is important for plant health, copper deficiency can lead to chlorosis (yellowing of leaves), and it does not activate nitrate reductase.
- **Zinc**: Important for various plant functions but does not activate nitrate reductase.

5. **Conclusion**:
- Based on the analysis, the element that activates the enzyme nitrate reductase during nitrogen fixation is **Molybdenum** (Option A).

### Final Answer:
The element that activates the enzyme nitrate reductase during nitrogen fixation is **Molybdenum**.

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