(a) Plasmolysis is process, which takes when a cell is placed in a hypertonic solution. During this process water moves out of the cell and the cell membrane of a plant cell shrinks away from its cell wall. When water moves out; it is first lost from the cytoplasm and then from the vacuole. The water when drawn out of the cell through diffusion into the extracellular (outside cell) fluid causes the protoplast to shrink away from the walls. The cell is said to be plasmolysed. The movement of water occurred across the membrane moving from an area of high water potential (i.e., the cell) to an area of lower water potential outside the cell. Eg. When grapes are immersed in sugar solution for few days we can see that the solution inside the grapes has moved out to the external medium making the grapes to shrink. (b) The process of plasmolysis is usually reversible when the plant cell is placed in solution, which has higher water potential. The water from the external solution enters into the plant cell causing the cytoplasm to build up a pressure against the cell wall called turgor pressure. Eg. When dry raisins are placed in pure water for few hours we can see that the water diffuses into the raisins making the cell turgid.