Close Up 1:Plants are about 90% water when properly hydrated. Its is a necessity to all of its functions, beginning with keeping itself upright. Water exerts turgor pressure onto the cell walls which keeps its form steady and helps with the process of growth. The overall hydration of the plant also directly affects the opening and closing of the stomata, which in tern affects the amount of CO2 the plant can take in, which limits the amount the plant can photosynthesize.