Which of the following is not a physiological role of potassium ?

Options

A. Maintain anion - cation balance in cells
B. Maintain turgidity of cells
C. Help in opening and closing of stomata
D. Synthesize auxins

Answer

To determine which of the following is not a physiological role of potassium, we will analyze each option based on the known functions of potassium in plants.

### Step-by-Step Solution:

1. **Understand the Role of Potassium**:
Potassium (K) is an essential macronutrient for plants, playing various physiological roles. It is involved in numerous processes that are vital for plant health and development.

2. **Evaluate Each Option**:
- **Option 1: Maintain cation and anion balance in cells**:
Potassium helps in maintaining the balance of cations and anions within plant cells, which is crucial for cellular function. This is indeed a physiological role of potassium.

- **Option 2: Maintain turbidity of cells**:
Potassium contributes to maintaining turgor pressure in cells, which is essential for keeping cells firm and maintaining plant structure. This is also a physiological role of potassium.

- **Option 3: Help in opening and closing of stomata**:
Potassium ions are critical in the regulation of stomatal movement, which facilitates gas exchange and transpiration in plants. This is another physiological role of potassium.

- **Option 4: Synthesize auxins**:
Auxins are a type of plant hormone that regulates growth and development. However, auxins are primarily synthesized from the amino acid tryptophan and are not synthesized from potassium. Therefore, this option does not represent a physiological role of potassium.

3. **Conclusion**:
Based on the analysis, the option that is not a physiological role of potassium is **Option 4: Synthesize auxins**.

### Final Answer:
**The correct answer is: Synthesize auxins.**

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