The lon involved in stomatal movement is:

Options

A. `Zn^(++)`
B. `Mg^(++)`
C. `Mn^(++)`
D. `K^(+)`

Answer

### Step-by-Step Solution:

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

2. **Role of Ions in Guard Cells**: The movement of specific ions into and out of guard cells is crucial for their turgidity, which directly affects the opening and closing of stomata.

3. **Identifying the Ion**: Among the given options (zinc ion, magnesium ion, manganese ion, and potassium ion), we need to determine which ion is involved in the stomatal movement.

4. **Potassium Ion Function**: When potassium ions (K+) enter the guard cells, they lower the water potential inside the cells. This causes water to move into the guard cells by osmosis, making them turgid (swollen).

5. **Effect of Turgidity**: The turgidity of guard cells leads to the opening of the stomata, allowing gas exchange to occur.

6. **Reverse Process**: When potassium ions exit the guard cells, the water potential inside the cells increases, causing water to leave the guard cells. This results in the guard cells becoming flaccid (shrunken) and leads to the closing of the stomata.

7. **Conclusion**: The ion that is primarily involved in the movement of stomata is the potassium ion.

### Final Answer:
The ion involved in stomatal movement is **potassium ion**.

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