Which of the following does not happened during stomatal opening ?

Options

A. Accumulation of `K^+` ion in guard cell
B. Increased TP of guard cell
C. Increased thickening of inner wall of guard cell
D. Decrease in pH of guard cell

Answer

To solve the question "Which of the following does not happen during stomatal opening?", we can analyze the processes involved in the opening of stomata and identify the statement that is incorrect.

### Step-by-Step Solution:

1. **Understanding Stomatal Opening**:
- Stomata are small openings on the surface of leaves that allow for gas exchange (CO2 in, O2 out) and transpiration (water vapor loss). The opening and closing of stomata are primarily controlled by guard cells.

2. **Role of Guard Cells**:
- Guard cells surround the stomatal pore and regulate its opening and closing. When guard cells take up water, they become turgid (swollen), which causes the stomatal pore to open.

3. **Potassium Ion Accumulation**:
- During stomatal opening, potassium ions (K+) are actively transported into the guard cells. This accumulation of potassium ions leads to an increase in osmotic pressure, causing water to enter the guard cells.

4. **Increased Turgor Pressure**:
- As water enters the guard cells due to the osmotic gradient created by potassium accumulation, the turgor pressure inside the guard cells increases. This pressure causes the guard cells to swell and the stomatal pore to open.

5. **Thinness of Inner Wall**:
- The inner wall of the guard cells becomes thinner as they swell. This is crucial for the opening of the stomatal pore. If the inner wall were to thicken, it would hinder the opening process.

6. **Decrease in pH**:
- The accumulation of potassium ions can lead to a decrease in the pH of the guard cells, making the environment more acidic.

7. **Identifying the Incorrect Statement**:
- Based on the above points, the statement that does not happen during stomatal opening is the "increased thickening of the inner wall of the guard cell." Instead, the inner wall becomes thinner.

### Conclusion:
The correct answer is that "increased thickening of the inner wall of the guard cell" does not happen during stomatal opening.