Opening and closing of stomata is due to

Options

A. pressure of gases inside the leaves
B. changes of turgor pressure in guard cells
C. effect of hormones
D. their genetic constitution

Answer

### Step-by-Step Solution:

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

2. **Role of Guard Cells**: Each stoma is surrounded by two guard cells. These cells are responsible for the opening and closing of the stomatal pore. The shape of guard cells is typically kidney or bean-shaped.

3. **Epidermis Layer**: The upper layer of the leaf is called the epidermis. It contains the guard cells and is important for protecting the leaf and regulating gas exchange.

4. **Turgor Pressure**: The opening and closing of stomata is primarily due to changes in turgor pressure within the guard cells. When guard cells take in water, they swell and become turgid, causing the stomatal pore to open.

5. **Mechanism of Opening**:
- When water enters the guard cells, the turgor pressure increases.
- This pressure causes the guard cells to bend away from each other, resulting in the opening of the stomatal pore.

6. **Mechanism of Closing**:
- When water leaves the guard cells (for instance, during water stress), the turgor pressure decreases.
- As a result, the guard cells become flaccid and shrink, causing the stomatal pore to close.

7. **Hormonal Influence**: While hormones like abscisic acid can influence the closing of stomata during water stress, the primary mechanism for the opening and closing of stomata is the change in turgor pressure in the guard cells.

8. **Conclusion**: Therefore, the opening and closing of stomata is primarily due to changes in turgor pressure in the guard cells.