How do sap vacuoles support plant cell turgor?

The central (sap) vacuole holds water and solutes, generating osmotic pressure that pushes the protoplast against the cell wall turgor. High turgor keeps cells rigid, supports leaves, and drives growth by controlled wall expansion. 

When solute accumulation in the vacuole increases water influx, turgor rises; solute export or water loss lowers turgor, causing wilting. Thus, vacuoles act as adjustable osmotic reservoirs that buffer drought and maintain cell shape.