Plants maintain water balance by opening and by closing stomata.
Explanation:
When plants are not getting enough water the tips as well as the edges of the leaves start drying and ultimately it turns brown in color. And when all the leaves turn brown the plant ultimately dies.
When light is travelling from the air to the water , the movement slows down and thus there is a little change in the direction. Thus we can say a light bend occurs when the light moves towards denser medium.