Plasmolysis occurs when cells are placed in a hypertonic solution and lose water due to osmosis. This allows us to correctly grasp osmosis and identify the semi-permeable nature of the cell wall.
In plasmolysis, cells in a hypertonic solution lose water (high concentration). The importance of plasmolysis is that it is a vital phenomenon since it explains the osmosis process. Plasmolysis displays the cell wall's permeability as well as the protoplasm's semipermeable character.
Since plasmolysis does not occur in a dead cell, it can be used to determine whether a cell is alive or dead.