Which of the following does not happen during the stomatal opening ?

Options

A. Turgor pressure of guard cell increases
B. `K^+` concentration in guard cell increases .
C. Thin outer walls bulge outwards .
D. Guard cell loose turgor due to water loss.

Answer

To solve the question "Which of the following does not happen during the stomatal opening?", we will analyze each option provided in the context of stomatal physiology.

### Step-by-Step Solution:

1. **Understanding Stomatal Opening**:
- Stomata are small openings on the surfaces of leaves that allow gas exchange. The opening and closing of stomata are primarily controlled by guard cells.
- When guard cells take up water, they become turgid (swollen), which causes the stomata to open.

2. **Analyzing Each Option**:
- **Option 1: Turgid pressure of the guard cell increases**:
- This is true. When guard cells become turgid, the pressure inside them increases, leading to the opening of the stomata.
- **Option 2: Potassium concentration in the guard cell increases**:
- This is also true. During stomatal opening, potassium ions (K+) are actively transported into the guard cells, leading to an increase in osmotic pressure and water influx.
- **Option 3: Thin outer wall bulges outward**:
- This is true as well. The turgidity of the guard cells causes the thin outer wall to bulge outward, facilitating the opening of the stomatal pore.
- **Option 4: Guard cell loses turgor due to water loss**:
- This is false. During stomatal opening, guard cells gain turgor pressure due to water influx. Losing turgor pressure occurs during stomatal closing, not opening.
- **Option 5: This type of event occurs during the closing of the stomata**:
- This is true. The loss of turgor pressure in guard cells, leading to stomatal closure, is indeed an event that occurs during the closing of the stomata.

3. **Conclusion**:
- The correct answer is **Option 4: Guard cell loses turgor due to water loss**. This event does not happen during stomatal opening; instead, it occurs during stomatal closing.

### Final Answer:
**Option 4: Guard cell loses turgor due to water loss.**