Question

Why are a plant's Stomata generally open during the day and closed at night?

Answer 1

So that during the day photosynthesis can happen and it closes at night so that the water doesn't evaporate<span />

Answer 2

Plants' stomata refers to the small pores that are found on plants' tissues and leaves. They possess the ability to open and close and thus they regulate water and gases exchange in plants. Green plants have the ability to produce their own food by using the energy from the sun;the process is called photosynthesis. During the day, when there is sunshine, the plants' stomata are always open in order to trap energy from the sun for photosynthesis. The stomata also allow carbon dioxide and oxygen gases to diffuse in and out of the leaves' cells.  The stomata usually closes at night in order to prevent excessive water loss.