Which of the following is not a role or function of magnesium

Options

A. It is used in the synthesis of cell wall, particularly as calcium pectate in the middle lamella.
B. It activates enzymes in respiration and photosynthesis, and in the synthesis of DNA and RNA.
C. It is a constituent of the ring structure of chlorophyll and maintains ribosome structure.
D. Deficiency of magnesium induces chlorosis between the leaf veins (interveinal chlorosis) and necrotic or purple coloured spots on older leaves.

Explanation

To determine which of the following is not a role or function of magnesium, we will analyze the functions of magnesium in plants and evaluate the provided options.

### Step-by-Step Solution:

1. **Understand the Role of Magnesium**: Magnesium is an essential macronutrient for plants, meaning it is required in larger amounts. It plays several critical roles in plant physiology.

2. **Identify Functions of Magnesium**:
- **Activator of Enzymes**: Magnesium acts as an activator for various enzymes, particularly those involved in photosynthesis and respiration. For example, it activates the enzyme Rubisco, which is crucial for carbon dioxide fixation.
- **Component of Chlorophyll**: Magnesium is a key component of chlorophyll, the green pigment in plants that is essential for photosynthesis.
- **Formation of Ribosomes**: Magnesium helps in maintaining the structure of ribosomes, which are vital for protein synthesis.
- **Involvement in DNA and RNA Synthesis**: Magnesium is also necessary for the synthesis of nucleic acids (DNA and RNA).

3. **Evaluate the Options**: Now, we will look at the options provided to identify which one does not pertain to the functions of magnesium:
- **Option 1**: "It is used in the synthesis of the cell wall particularly as calcium pectate in the middle lamina."
- **Option 2**: "It activates the enzyme in respiration and photosynthesis and in the synthesis of the DNA and RNA."
- **Option 3**: "The deficiency of magnesium induces chlorosis between the leaf veins and necrotic or purple-colored spots on the older leaves."

4. **Determine the Incorrect Function**:
- **Option 1** is incorrect because magnesium is not involved in the synthesis of the cell wall; that role is primarily attributed to calcium, which forms calcium pectate in the middle lamina.
- **Option 2** is true as magnesium does activate enzymes and is involved in DNA and RNA synthesis.
- **Option 3** is also true since magnesium deficiency leads to chlorosis and necrotic spots.

5. **Conclusion**: The option that is not a function of magnesium is **Option 1**.

### Final Answer:
The correct answer is **Option 1**: "It is used in the synthesis of the cell wall particularly as calcium pectate in the middle lamina."

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