Magnesium is an essential nutrient because it is

Options

A. required in large quantity
B. absorbed by the plant
C. not replaced by another element
D. found in the ash analysis

Answer

**Step-by-Step Solution:**

1. **Understanding Magnesium's Role**: Magnesium is recognized as an essential nutrient for plants and animals. It plays a crucial role in various biological processes.

2. **Cofactor for Enzymes**: One of the key reasons magnesium is essential is that it acts as a cofactor for over 300 enzymes. This means that magnesium is necessary for these enzymes to function properly.

3. **Importance in Calcium-Potassium Channels**: Magnesium is involved in the transport of ions, particularly in the calcium-potassium channels within cells. This is important for various cellular functions, including nerve signal transmission.

4. **Bone Development**: Magnesium is also vital for bone development. It is one of the components of bone tissue, along with calcium and phosphorus, and is necessary for maintaining bone health.

5. **Absorption and Replacement**: While magnesium is absorbed in large quantities by plants and cannot be replaced by other elements, these factors alone do not define its essentiality. The inability to replace magnesium with another element in its specific roles is a significant reason for its classification as an essential nutrient.

6. **Conclusion**: Therefore, magnesium is considered an essential nutrient primarily because it acts as a cofactor in numerous enzymatic reactions and cannot be substituted by other elements in these processes.

**Final Answer**: Magnesium is an essential nutrient because it acts as a cofactor in over 300 enzymes and cannot be replaced by another element.

---