Which of the following mineral nutrients plays an important role in biological nitrogen fixation?

Options

A. Zinc
B. Iron
C. Molybdenum
D. Magnesium

Explanation

**Step-by-Step Solution:**

1. **Understanding Biological Nitrogen Fixation:**
- Biological nitrogen fixation is the process by which atmospheric nitrogen (N₂) is converted into ammonia (NH₃) by certain microorganisms, primarily bacteria. This process is essential for making nitrogen available to plants in a form they can utilize.

2. **Identifying the Role of Mineral Nutrients:**
- Various mineral nutrients are involved in plant growth and metabolic processes. Among these, some play specific roles in nitrogen fixation.

3. **Recognizing the Key Mineral Nutrient:**
- The mineral nutrient that plays a crucial role in biological nitrogen fixation is Molybdenum (Mo). It is classified as a microelement, meaning it is required in small quantities by plants.

4. **Absorption of Molybdenum:**
- Molybdenum is absorbed by plants in the form of molybdate ions (MoO₂⁻). This form is utilized by plants to perform essential functions.

5. **Enzymatic Functions of Molybdenum:**
- Molybdenum is a vital component of several enzymes, particularly nitrogenous enzymes and nitrate reductase. These enzymes are critical for the conversion of nitrogen into ammonia during the nitrogen fixation process.

6. **Conclusion:**
- Therefore, the mineral nutrient that plays an important role in biological nitrogen fixation is Molybdenum.

**Final Answer: Molybdenum**

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