Q- Working of stomata?
During day time when water flow into the guard cell they get swell up and become curved it cause opening of stomata. During day time the starch of guard cell get converted into sugar that increases osmotic content of the guard cell.
During night time the sugar is converted back into starch that lead to osmotic pressure should be increases. Gases in and out of plants through stomata during process of respiration and photosynthesis. The direction of diffusion depends upon the environmental condition and need of the plant.