Question

Explains how the opening and closing of the stomata change the role of photosynthesis.

Answer 1

If the stomata were constantly open, plants would lose too much water via evaporation from the leaf surface, a process called transpiration. ... This is the basis for the opening and closing of a stoma, known as stomatal movement, which controls gas exchange necessary for photosynthesis and limits water loss.

Answer 2

The opening and closing of the pore is a function of the guard cells. The guard cells swell when water flows into them, causing the stomatal pore to open. Simillarly the pore closes if the guard cells shrink