During stomatal opening (photo-active) which does not occur?

Options

A. Increase in pH of guard cells
B. Hydrolysis of starch in guard cells
C. Increased TP of subsidiary cells
D. Dissociation of malic acid in guard cells

Answer

To solve the question "During stomatal opening (photo-active) which does not occur?", we will analyze each of the provided options based on our understanding of stomatal physiology.

### Step-by-Step Solution:

1. **Understanding Stomatal Opening**:
- Stomata are small openings on the surface of leaves that allow for gas exchange. Their opening and closing are primarily controlled by guard cells.
- During stomatal opening, certain physiological changes occur in the guard cells.

2. **Analyzing Each Option**:
- **Option 1: Increase in the pH of the guard cells**:
- When stomata open, the pH of guard cells increases due to the accumulation of potassium ions (K+) and the movement of protons (H+). This is a correct statement.

- **Option 2: Hydrolysis of the starch in the guard cells**:
- Starch stored in guard cells is hydrolyzed to glucose, which is then used to generate osmotic pressure, leading to the opening of the stomata. This is also a correct statement.

- **Option 3: Increased turgor pressure (Tp) of the subsidiary cells**:
- The opening of stomata is primarily due to increased turgor pressure in the guard cells, not the subsidiary cells. Therefore, this statement is incorrect.

- **Option 4: Dissociation of the malic acid in the guard cells**:
- Malic acid dissociates into malate and protons, which contributes to the osmotic potential and helps in the opening of the stomata. This is a correct statement.

3. **Conclusion**:
- The only option that does not occur during stomatal opening is **Option 3: Increased turgor pressure of the subsidiary cells**.

### Final Answer:
**Increased turgor pressure (Tp) of the subsidiary cells does not occur during stomatal opening.**

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