How do the guard cells regulate opening and closing of stomatal pores?

Opening of guard cells is facilitated by the entry of water inside guard cells. This make the guard cell become turgid. Closing of guard cells is facilitated by water coming out of guard cells. This will make the guard cells flaccid.

Entry of water inside guard cells will make the cell turgid leading to the opening of stomata. Similarly cell become flaccid when water come out of guard cells, this leads to closing of the stomata.