The stomatal movements are due to

Options

A. Pressure of water vapour inside
B. turgor pressure of guard cells
C. Genetic constitution
D. None of these

Answer

**Step-by-Step Solution:**

1. **Understanding Stomata**: Stomata are small openings on the surface of leaves that facilitate gas exchange and transpiration (the loss of water vapor).

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 stomata.

3. **Mechanism of Stomatal Movement**: The opening and closing of stomata are primarily due to changes in the turgidity (internal pressure) of the guard cells.

4. **Turgidity Changes**:
- When guard cells absorb water (often due to the uptake of ions), they become turgid (swollen with water), causing the stomata to open.
- Conversely, when guard cells lose water (due to ion loss or water stress), they become flaccid (soft and limp), leading to the closing of the stomata.

5. **Identifying the Correct Answer**: The question asks what causes stomatal movements. The primary factor is the turgor pressure of the guard cells, which is influenced by water movement. Therefore, the correct answer is "target pressure of guard cells."

6. **Elimination of Other Options**:
- The pressure of water vapors inside the leaf does not directly cause stomatal movement.
- Genetic constitution does not play a direct role in the immediate opening and closing of stomata.

**Final Answer**: The stomatal movements are due to the target pressure of guard cells.

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