The change in turgor pressure which causes the opening and closing of Stomata is caused by :(

Options

A. Reversible starch-sugar conversions
B. Reversible absorption and loss of K-ions
C. Loss of chloride ions
D. None of these

Answer

To solve the question regarding the change in turgor pressure that causes the opening and closing of stomata, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Stomata Function**: Stomata are small openings on the surface of leaves that allow for gas exchange. The opening and closing of stomata are crucial for regulating water loss and gas exchange in plants.

2. **Role of Turgor Pressure**: Turgor pressure is the pressure exerted by the fluid (water) inside the vacuole of plant cells against the cell wall. This pressure is essential for maintaining the structure of the plant cells and plays a significant role in the opening and closing of stomata.

3. **Factors Affecting Turgor Pressure**: The turgor pressure in guard cells (the cells surrounding stomata) changes due to the absorption or loss of water and ions, particularly potassium ions (K+).

4. **Analyzing the Options**:
- **Option A: Reversible starch-sugar conversion** - This option is incorrect as it does not directly relate to the turgor pressure changes in guard cells.
- **Option B: Reversible absorption and loss of potassium ions** - This option is correct. The absorption of potassium ions into guard cells causes water to enter the cells by osmosis, increasing turgor pressure and leading to the opening of stomata. Conversely, the loss of potassium ions leads to water leaving the cells, decreasing turgor pressure, and causing the stomata to close.
- **Option C: Other processes** - This option is incorrect as it does not specify a mechanism related to turgor pressure.
- **Option D: None of these** - This option is also incorrect as we have identified a correct mechanism.

5. **Conclusion**: The correct answer to the question is **Option B: Reversible absorption and loss of potassium ions**.