Active `K^(+)` exchange mechanism for opening and closing of stomata was given by

Options

A. Darwin
B. Levitt
C. Scarth
D. Khorana

Answer

To solve the question regarding the active potassium exchange mechanism for the opening and closing of stomata, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Stomata**: Stomata are small openings on the surface of leaves that allow for gas exchange. They are surrounded by guard cells that regulate their opening and closing.

2. **Role of Potassium Ions (K⁺)**: Potassium ions play a crucial role in the functioning of guard cells. When K⁺ ions are actively transported into the guard cells, they cause a change in the water potential of these cells.

3. **Water Potential and Guard Cell Turgidity**: The influx of K⁺ ions into the guard cells decreases the water potential inside the cells. As a result, water moves into the guard cells by osmosis, causing them to swell and become turgid.

4. **Opening of Stomata**: The swelling of the guard cells due to increased turgor pressure leads to the opening of the stomatal pore, allowing for gas exchange.

5. **Closing of Stomata**: Conversely, when K⁺ ions exit the guard cells, the water potential inside the cells increases. This causes water to move out of the guard cells, leading to a decrease in turgor pressure and resulting in the closing of the stomatal pore.

6. **Identifying the Theory**: The mechanism of active potassium exchange that regulates the opening and closing of stomata was proposed by Levitt.

7. **Final Answer**: Therefore, the correct answer to the question is Levitt.