What is the result of water moving into guard cells during potassium ion influx?

The correct answer is that the guard cells swell unevenly due to differing wall thickness. When potassium ions enter the guard cells, this causes water to move into the cells via osmosis, as water follows the concentration gradient created by the influx of potassium.

The structure of guard cells is such that the inner walls are thicker and less flexible compared to the outer walls. As water fills the guard cells, the thicker inner walls resist bending, leading to a disproportionate expansion. This unequal swelling causes the guard cells to curve away from each other, which opens the stomata, allowing gas exchange to occur. This mechanism is crucial for plant physiology, especially in regulating water loss and gas exchange during photosynthesis.

The other options do not accurately describe this process. For instance, guard cells do not decrease in size or become impermeable to water when they engage in this response. Additionally, the stoma does not close during the influx of potassium and subsequent water entry; instead, this process facilitates the opening of the stomata.