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 option is not a criterion for the essentiality of an element according to Arnon and Stout, we will analyze the criteria they established in 1939. Here is a step-by-step solution:

### Step 1: Understand the Criteria for Essentiality
Arnon and Stout proposed specific criteria to determine whether an element is essential for plant growth. These criteria include:
1. The element must be indispensable for the growth of the plant.
2. The plant must be unable to complete its vegetative and reproductive phases in the absence of the element.
3. The element must be irreplaceable by any other element.
4. The absence of the element must produce specific disorders in the plant.

### Step 2: Analyze Each Option
Now, we will analyze the options provided in the question to identify which one does not align with the criteria established by Arnon and Stout.

- **Option A**: The element is indispensable for the growth of the plant. (This is a correct criterion.)
- **Option B**: A plant is unable to complete its vegetative and reproductive phase in the absence of the element. (This is also a correct criterion.)
- **Option C**: The element is replaceable by other elements. (This is NOT a correct criterion; the element must be irreplaceable.)
- **Option D**: The absence of the element produces disorders. (This is a correct criterion.)

### Step 3: Identify the Incorrect Statement
From the analysis, we can see that Option C states that the element is replaceable by other elements, which contradicts the criteria established by Arnon and Stout that the element must be irreplaceable.

### Conclusion
The option that is not a criterion for essentiality of an element according to Arnon and Stout is **Option C**.

---