Which of the following is not an essential micronutrient ?

Options

A. Boron
B. Sodium
C. Manganese
D. Molybdenum

Answer

To determine which of the following is not an essential micronutrient, we will analyze each option provided: Boron, Sodium, Magnesium, and Molybdenum.

### Step-by-Step Solution:

1. **Understanding Micronutrients**:
- Micronutrients are nutrients required by plants in very small quantities. They are essential for various physiological functions and overall plant growth.

2. **Classifying Micronutrients**:
- Micronutrients can be classified into two categories: essential and non-essential.
- Essential micronutrients are critical for plant growth and development. Their absence can lead to significant growth issues.
- Non-essential micronutrients are beneficial but not mandatory for plant growth. Their absence does not critically affect the plant.

3. **Analyzing Boron**:
- Boron is classified as an essential micronutrient. It plays a crucial role in cell wall formation and cell division. Therefore, it is not the correct answer.

4. **Analyzing Sodium**:
- Sodium is considered a non-essential micronutrient. While it can assist in certain metabolic processes and enhance growth, it is not mandatory for plant survival. Thus, this could be the correct answer.

5. **Analyzing Magnesium**:
- Magnesium is an essential micronutrient. It is vital for chlorophyll synthesis and plays a key role in photosynthesis. Therefore, it is not the correct answer.

6. **Analyzing Molybdenum**:
- Molybdenum is also an essential micronutrient. It is important for nitrogen fixation and is a component of enzymes involved in amino acid synthesis. Thus, it is not the correct answer.

7. **Conclusion**:
- Among the options provided, Sodium is the only one that is classified as a non-essential micronutrient. Therefore, the answer to the question is Sodium.

### Final Answer:
**Sodium is not an essential micronutrient.**

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