Explain how light influences stomatal opening in a plant that has been previously in the dark.

When exposed to light, starch of the guard cells is converted into malic acid, Malic acid dissociate into malate and H+ ions in the guard cells.

H+ ions are transported to epidermal cells and H+ and K+ ions enter the guard cells.

Increase in K+ and malate ions in the guard cells increases their osmotic pressure and more water enters from the surrounding cells by osmosis.

The turgidity of the guard cells increases, making them to draw the stomata open apart opening the stomata.