The cause of the opening or closing of the stomata mainly depends on change in the turgidity of

Options

A. Microfibrils
B. Guard cells
C. Epidermal cells
D. Xylem

Answer

**Step-by-Step Solution:**

1. **Understanding Stomata Function**: The stomata are small openings on the surface of leaves that allow for gas exchange. Their opening and closing are primarily controlled by guard cells.

2. **Role of Guard Cells**: Guard cells are specialized cells that surround each stoma. They have a unique bean or kidney shape that allows them to change shape when turgidity changes, which in turn opens or closes the stomata.

3. **Mechanism of Opening Stomata**:
- When potassium ions (K+) are actively transported into the guard cells, the water potential inside the guard cells decreases.
- This decrease in water potential causes water to move into the guard cells from the surrounding cells due to osmosis.

4. **Increase in Turgor Pressure**: As water enters the guard cells, the turgor pressure (the pressure of the cell contents against the cell wall) increases. This increase in turgidity causes the guard cells to swell and change shape, resulting in the opening of the stomata.

5. **Mechanism of Closing Stomata**: Conversely, when potassium ions exit the guard cells, the water potential inside the guard cells increases, leading to water moving out of the guard cells. This results in a decrease in turgor pressure, causing the stomata to close.

6. **Conclusion**: The opening and closing of stomata depend mainly on the turgidity of the guard cells, which is influenced by the movement of potassium ions and water.

**Final Answer**: The cause of the opening or closing of the stomata mainly depends on the change in the turgidity of the **guard cells**.

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