Which of the following characteristics defines an element as essential element for a particular species

Options

A. If it is missing a plant cannot grow or reproduce normally.
B. If it is absent other nutrients may be substituted for it
C. If it is present in high concentration plant growth increases
D. For high seed production it has to be added as a fertilizer

Answer

To determine which characteristic defines an element as an essential element for a particular species, we can analyze the options provided:

1. **If it is missing, a plant cannot grow or reproduce normally.**
- This statement is true for essential elements. Essential elements are those that are required for the normal growth and reproduction of a plant. If these elements are absent, the plant will exhibit deficiencies that can hinder its growth and reproductive capabilities.

2. **If it is absent, other nutrients may be substituted for it.**
- This statement is incorrect. Essential elements cannot be substituted by other nutrients. Each essential element has a specific role in plant metabolism that cannot be fulfilled by another nutrient.

3. **If it is present in a high concentration, plant growth increases.**
- This statement is misleading. While some nutrients are required in larger quantities, simply having them in high concentrations does not necessarily correlate with increased growth. In fact, excessive amounts can be toxic.

4. **For high seed production, it has to be added as a fertilizer.**
- This statement is also incorrect. While fertilizers can provide essential nutrients, the presence of an essential element is not solely dependent on its addition through fertilizers. It must be available in the soil for the plant to utilize.

5. **For high seed production, as a fertilizer, we cannot give an essential element.**
- This statement is incorrect. Essential elements can indeed be provided through fertilizers to enhance growth and seed production, but their essentiality is not defined by their application as fertilizers.

Based on this analysis, the characteristic that defines an element as an essential element for a particular species is:

**Correct Answer: Option 1 - If it is missing, a plant cannot grow or reproduce normally.**