An immobile element in plants is

Options

A. calcium
B. potassium
C. phosphorus
D. nitrogen

Answer

**Step-by-Step Solution:**

1. **Understanding the Question:**
The question asks for an immobile element in plants. An immobile element is one that does not move from its original location within the plant.

2. **Identifying the Options:**
The options provided are:
- A. Calcium
- B. Potassium
- C. Phosphorus
- D. Nitrogen

3. **Analyzing Each Element:**
- **Calcium (A):** Calcium is known to be a structural component in plants, particularly in the cell wall where it is found as calcium pectate. This structural role makes it immobile.
- **Potassium (B):** Potassium is a mobile element that can move within the plant to where it is needed.
- **Phosphorus (C):** Phosphorus is also considered a mobile element, especially in its phosphate form, and can be relocated within the plant.
- **Nitrogen (D):** Nitrogen is mobile and can be transported within the plant tissues.

4. **Conclusion:**
Among the options, calcium is identified as the most immobile element due to its role in the structural integrity of the cell wall. Therefore, the correct answer is A. Calcium.

**Final Answer:**
The immobile element in plants is A. Calcium.

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