Final answer:
Guard cells regulate stomata by using osmosis and active transport to allow for gas exchange necessary for photosynthesis while controlling transpiration. Active transport involves ions moving into or out of guard cells affecting their volume, and osmosis follows with water moving accordingly, leading to stomata opening or closing.
Step-by-step explanation:
The opening and closing of stomata are regulated by guard cells, which are specialized cells surrounding the stomatal pores on leaves. Active transport and osmosis are two processes that play a crucial role in this regulatory function. Guard cells control the opening of stomata by changing their volume. When guard cells swell, they create an opening for the stomata, allowing for gas exchange necessary for photosynthesis. This swelling is a result of water entering the cells via osmosis, driven by the active transport of ions, particularly potassium (K+) and hydrogen ions (H+), into the guard cells, increasing their osmotic pressure.
Conversely, when these ions are actively transported out of the guard cells, the osmotic pressure decreases, causing water to leave the cells, resulting in the guard cells shrinking and stomata closing. This closure helps to reduce water loss through transpiration, especially under stress conditions such as drought, high temperature, or darkness. Thus, the processes of osmosis and active transport are vital for plants to maintain a balance between efficient photosynthesis and minimal water loss.