The Opening and Closing of the Stomatal pore Depends upon (1) Oxygen (2) Temperature (3) Water in Guard Cells (4) Concentration of CO2 in Stomata

Answer: 

(3) Water in guard cells

Stomata are pore-like structures that help leaves in exchanging gases and transpiration. These pores are present on the surface of the leaves. The opening and closing of the pores are guarded by the entry of water into the guard cells. Then these guard cells become flaccid and lead to stomatal closure. The opening and closing of the pores depend on the pressure that occurred due to the osmotic flow of water. The stomatal pores open when the light strikes the leaf and closes at night.