The immediate cause of the opening and closing of stomata is :

Options

A. Change in turgidity of guard cells
B. Flaccidity of guard cell
C. Orientation of microfibrills
D. Turgidity of subsidiary cells

Answer

### Step-by-Step Solution:

1. **Understanding Stomata**: Stomata are small openings on the surface of leaves that facilitate gas exchange between the plant and the environment. They play a crucial role in photosynthesis and transpiration.

2. **Role of Guard Cells**: Each stoma is surrounded by two specialized cells known as guard cells. These cells control the opening and closing of the stomatal pore.

3. **Turgidity of Guard Cells**: The immediate cause of stomatal opening and closing is the change in turgidity of the guard cells. Turgidity refers to the state of being swollen or firm due to the uptake of water.

4. **Mechanism of Opening**: When light is present, guard cells absorb water through osmosis, becoming turgid. This increased turgidity causes the guard cells to swell and the stomatal pore to open, allowing gas exchange to occur.

5. **Mechanism of Closing**: Conversely, during the night or in conditions of water loss, guard cells lose water and become flaccid. This flaccidity causes the stomatal pore to close, reducing water loss and conserving resources.

6. **Evaluating Options**:
- Option 1: Change of the turgidity of the guard cells - This is correct.
- Option 2: Flaccidity of guard cells - This is incorrect as flaccidity leads to stomatal closure.
- Option 3: Orientation of the microfibrils - This is not directly related to the immediate cause of stomatal movement.
- Option 4: Turgidity of the subsidiary cells - This is also incorrect as it does not directly cause stomatal opening or closing.

7. **Conclusion**: The immediate cause of the opening and closing of stomata is the change in turgidity of the guard cells.

### Final Answer:
The immediate cause of the opening and closing of stomata is the change of the turgidity of the guard cells.

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