Hypertonic solution is more concentrated as compared to standard solution. If a plant cell is placed in highly concentrated salt or sugar solution (hypertonic solution), water from the cell sap flows out due to exosmosis through the plasma membrane outside the cell. Loss of water from the cell sap causes contraction or shrinkage of proptoplast. This is referred to as plasmolysis. Hypertonic solution occupies the space between the cell wall and shrunken protoplast in a plasmolysed cell.