Essential mineral nutrients are the elements

Options

A. In the absence of which plants cannot complete their life cycle
B. Which cannot be replaced by other element in its function
C. Which are directly associated with the plant metabolism
D. All of the above

Answer

### Step-by-Step Solution:

1. **Understanding Essential Mineral Nutrients**: Essential mineral nutrients are elements that are crucial for plant growth and development. They are required for various physiological and biochemical processes in plants.

2. **Criteria for Essentiality**: There are three main criteria that determine whether a mineral nutrient is essential for plants:
- **Criterion 1**: The element must be absolutely necessary for supporting normal growth and reproduction.
- This means that without this element, plants cannot complete their life cycle or produce seeds.
- **Criterion 2**: The requirement of the element must be specific and cannot be replaced by any other element.
- This indicates that if a plant lacks a specific nutrient, it cannot substitute it with another nutrient to fulfill its needs.
- **Criterion 3**: The element must be directly involved in the metabolism of the plant.
- This means that the element plays a direct role in the biochemical processes that occur within the plant.

3. **Classification of Essential Nutrients**: Based on the above criteria, essential mineral nutrients are classified into two categories:
- **Macronutrients**: These are required in larger quantities (e.g., nitrogen, phosphorus, potassium).
- **Micronutrients**: These are needed in smaller quantities (e.g., iron, manganese, zinc).

4. **Conclusion**: Therefore, essential mineral nutrients are elements that are necessary for plant growth, cannot be replaced by other elements, and are directly involved in plant metabolism. Thus, the answer to the question is that essential mineral nutrients are the elements that fulfill all these criteria.

### Final Answer:
Essential mineral nutrients are the elements in the absence of which plants cannot complete their life cycle, which cannot be replaced by other elements in their function, and which are directly associated with plant metabolism.

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