Mark the correct statement .

Options

A. The osmotic pressure of guard cells in highest when the stomata are open and the lowest when the stomata are closed.
B. The osmotic pressure of guard cells is lowest when the stomata are open and the highest when the stomata are closed.
C. The osmotic pressure of guard cells and epidermal cells surrounding it never matters for the opening of stomata .
D. (2) and (3) are correct

Answer

To solve the question regarding the correct statement about the osmotic pressure of guard cells in relation to the opening and closing of stomata, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Function of Stomata**:
- Stomata are small openings on the surface of leaves that allow for gas exchange (CO2 in, O2 out) and transpiration (water vapor loss). They are surrounded by guard cells that control their opening and closing.

2. **Analyze the Guard Cells**:
- Guard cells have thicker inner walls and thinner outer walls. This structural difference is crucial for their function in regulating the size of the stomatal pore.

3. **Osmotic Pressure and Water Movement**:
- When guard cells take up water (become turgid), they swell and the stomata open. This occurs when the osmotic pressure inside the guard cells is high.
- Conversely, when guard cells lose water (become flaccid), the stomata close. This happens when the osmotic pressure inside the guard cells is low.

4. **Evaluate the Statements**:
- **Statement 1**: "The osmotic pressure of the guard cell is highest when the stomata is open and lowest when the stomata is closed."
- This statement is **correct** because high osmotic pressure leads to turgidity and stomatal opening.
- **Statement 2**: "The osmotic pressure of the guard cell is lowest when the stomata is open and highest when the stomata is closed."
- This statement is **incorrect** as it contradicts the physiological process described above.
- **Statement 3**: "The osmotic pressure of the guard cell and epidermal cell surrounding it never matters for the opening of stomata."
- This statement is also **incorrect** because the osmotic pressure of guard cells is crucial for stomatal function.

5. **Conclusion**:
- Based on the analysis, the correct statement is the first one. Therefore, the answer is **Option A**.