They open the stomata during the day to collect light energy from the sun and carbon dioxide from the atmosphere, i.e adaptation.
Explanation:
Plants also responds to hormones such as abscisic acid that causes the stomata to close during stressful conditions. During the day the mesophyll in a leaf requires the stomata to open for exposure to sunlight and carbon dioxide. It closes at night when there is no sunlight to prevent water loss through transpiration in response to the turgidity of guard cells.
