The Brainliest Answer!

when the vacuoles in guard cells are filled with water(cell sap) ,the cell enlarges(turgidity).. but during sunny days,the vacuoles lose cell sap and the guard cells shrink.

when the guard cells enlarge due to filled vacuoles its thick inner wall arches and opens the stomata facilitating diffusion of gases and transpiration..when the guard sells lose water and shrink, the stomata closes 

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