Which one of the following is not a criteria for essentiality of an element according to arnon and stout?

Options

A. It is indispensible for the growth of the plant
B. A plant is unable to complete its vegetative or reproductive phase in the absence of the element.
C. The element is replaceable
D. The absence of the element produces disorders

Answer

To determine which of the following is not a criterion for essentiality of an element according to Arnon and Stout, we need to review the criteria they proposed in 1939. Here’s a step-by-step breakdown of the criteria and the evaluation of the options:

### Step 1: Understand the Criteria for Essentiality
1. **Indispensability**: An essential element must be indispensable for the growth of the plant. This means the plant cannot grow normally without it.
2. **Direct Involvement in Metabolism**: The element must be directly involved in the plant's metabolism.
3. **Completion of Growth Phases**: The absence of the element must prevent the plant from completing its vegetative and reproductive phases.
4. **Non-replaceability**: The essential element cannot be replaced by another element. If another element can substitute for it, then it is not considered essential.
5. **Deficiency Disorder**: The absence of the element must lead to a disorder or deficiency in the plant.

### Step 2: Evaluate the Options
Now, we will evaluate the options provided in the question against the criteria outlined above.

- **Option 1**: The element should be indispensable for the growth of the plant. (This is correct)
- **Option 2**: A plant will be unable to complete its vegetative and reproductive phases in its absence. (This is correct)
- **Option 3**: The element will be replaceable. (This is incorrect; essential elements cannot be replaced by others)
- **Option 4**: The absence of the element will produce a disorder. (This is correct)

### Step 3: Identify the Incorrect Criterion
From the evaluation, we can see that **Option 3**, which states that the element will be replaceable, does not align with Arnon and Stout's criteria. Therefore, this is the correct answer to the question.

### Conclusion
The answer to the question "Which one of the following is not a criterion for essentiality of an element according to Arnon and Stout?" is **Option 3: The element will be replaceable.**

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