Which one gives the most valid and recent explanation for stomatal movements?

Options

A. Potassium influx and efflux
B. Starch hydrolysis
C. Guard cell photosynthesis
D. Transpiration

Answer

### Step-by-Step Solution:

1. **Understanding Stomatal Movements**: Stomatal movements refer to the opening and closing of stomata, which are small pores located on the surfaces of leaves. These movements are crucial for gas exchange, light entry, and transpiration.

2. **Role of Guard Cells**: Stomata are surrounded by guard cells that regulate their opening and closing. When guard cells swell, they open the stomatal pore, and when they lose water, they close the pore.

3. **Mechanism of Opening**: The opening of stomata occurs when guard cells accumulate potassium ions (K+). This accumulation leads to a decrease in water concentration inside the guard cells, causing water to enter the cells through osmosis. As water enters, the guard cells become turgid (swollen), resulting in the opening of the stomatal pore.

4. **Mechanism of Closing**: Conversely, when the guard cells lose potassium ions, the water concentration inside the cells increases. This causes water to exit the guard cells, leading to a flaccid state (loss of turgor) and the closing of the stomatal pore.

5. **Conclusion**: The most valid and recent explanation for stomatal movements is the mechanism of potassium influx and efflux. This process is responsible for the changes in turgor pressure within guard cells, leading to the opening and closing of stomata.

### Final Answer:
The most valid and recent explanation for stomatal movements is **potassium influx and efflux**.

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