`K^(+)` ions control

Options

A. opening and closing of stomata
B. guttation
C. formation of mitotic spindle
D. all of these

Answer

**Step-by-Step Solution:**

1. **Understanding the Role of Potassium Ions (K⁺)**: Potassium ions are essential nutrients for plants, playing a critical role in various physiological processes.

2. **Identifying Key Functions**:
- Potassium is crucial for protein synthesis.
- It is particularly important for the regulation of stomatal movement.

3. **Focusing on Stomatal Movement**:
- The opening and closing of stomata are controlled by guard cells, which change their turgidity based on the concentration of potassium ions.
- Proton pumps in the guard cells help in regulating the movement of potassium ions, leading to changes in turgidity (turgid when K⁺ is high, flaccid when K⁺ is low).

4. **Evaluating the Options**:
- **Option A**: Opening and closing of stomata - This is a primary function of potassium ions.
- **Option B**: Guttation - While potassium may play a role, it is not the primary control mechanism.
- **Option C**: Formation of mitotic spindle - This is primarily controlled by other factors, not potassium ions.
- **Option D**: All of these - Since not all options are correct, this cannot be the answer.

5. **Conclusion**: The most accurate answer is **Option A**, as potassium ions primarily control the opening and closing of stomata in plants.

**Final Answer**: Option A - Opening and closing of stomata.

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