Answer: The stomata bring in the CO2 from the air to create sugar.

In plants, photosynthesis can occur without dark reactions using an electron donor such as water, but not with a light-driven energy source such as sunlight. In plants, light is used to power a chemical reaction called photophosphorylation that results in the generation of AMP and NADPH from organic compounds under conditions of high carbon dioxide levels. AMP and NADPH provide “electron donors” needed for reversed luciferase-catalyzed breakdown of ATP produced during the period before thylakoid membranes bound pigment increase thylakoid membrane potential by transferring electrons from themselves through quinones to Q cycle enzymes then on finally ATP synthase. The energy stored in that ATP provides the power to drive the formation of glucose during the Calvin cycle, which produces sugar (glucose) for storage as starch (in plant seeds, grains, or tubers; in algae it’s often oil).