A metal ion involved in stomatal regulation is

Options

A. Iron
B. Potassium
C. Zinc
D. Magnesium

Answer

**Step-by-Step Solution:**

1. **Understanding Stomatal Regulation:**
- Stomata are small openings on the surface of leaves that regulate gas exchange and water loss in plants. The opening and closing of stomata are controlled by specialized cells called guard cells.

2. **Role of Guard Cells:**
- Guard cells surround each stoma and change shape to open or close the stomatal pore. When guard cells take in water, they swell and become turgid, causing the stomatal pore to open.

3. **Mechanism of Opening:**
- The opening of stomata occurs when potassium ions (K+) move into the guard cells. This influx of potassium ions lowers the water potential inside the guard cells, leading to water entering the cells by osmosis. The turgidity of the guard cells pushes the thin outer wall outward, which in turn pulls the thick inner wall, resulting in the opening of the stomatal pore.

4. **Mechanism of Closing:**
- Conversely, when the guard cells lose water, they become flaccid. This happens when potassium ions move out of the guard cells, increasing the water potential inside the cells. As a result, water exits the guard cells, leading to their flaccidity and causing the stomatal pore to close.

5. **Conclusion:**
- The metal ion that plays a crucial role in the regulation of stomata is potassium (K+). It is essential for both the opening and closing of the stomatal pore through its movement in and out of guard cells.

**Final Answer:**
The metal ion involved in stomatal regulation is potassium (K+).

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