Opening and closing of stomata is due to the

Options

A. hormonal change in guard cells.
B. change in turgor pressure of guard cells.
C. gaseous exchange.
D. respiration

Answer

**Step-by-Step Solution:**

1. **Understanding Stomata**: Stomata are small openings found on the surface of leaves that facilitate gas exchange. They allow carbon dioxide to enter the leaf for photosynthesis and oxygen to exit.

2. **Role of Guard Cells**: Each stoma is surrounded by two specialized cells known as guard cells. These cells are responsible for regulating the size of the stomatal opening.

3. **Turgor Pressure**: The opening and closing of stomata is primarily controlled by the turgor pressure within the guard cells. Turgor pressure is the pressure exerted by the fluid inside the cell against the cell wall.

4. **Mechanism of Opening and Closing**:
- When guard cells take up water, they become turgid (swollen), which causes the stomata to open.
- Conversely, when guard cells lose water, they become flaccid (soft), leading to the closing of the stomata.

5. **Conclusion**: The correct reason for the opening and closing of stomata is due to changes in turgor pressure in the guard cells. Therefore, the answer is option 2: change in turgor pressure of guard cells.

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