Osmosis in plant cells

Osmosis is the way in which plants take up water. This is how. Root hairs of the plant take in water from the soil by osmosis. The cell membrane of the root hair cell acts a partially permeable membrane (the cell wall is fully permeable) and because the cell sap inside the vacuole is a strong solution (low water concentration) water passes from the soil (high water concentration) into the root hair cell by osmosis. The concentration of the sap in the vacuole is now weaker as there is a high concentration of water. Water will now pass from this area of high concentration to the next cell which has a low water concentration by osmosis. In this way water continues to move along the cells of the root up the xylem to the leaf. all the time water is moving to areas of lower water concentration

As water enters plant cells it makes the cell swell up. The water moves into the plant cell vacuole and pushes against the cell wall. Eventually the cell contains as much water as it can hold. The strong cell wall stops the cell bursting. We say that cell is turgid. Turgid cells are useful implants as the give the plant support as they keep the stems of plants upright.



When plants are placed into a strong sugar or salts solution water will pass out of the cells by osmosis. As water passes out, the sap vacuole starts to shrink. These cells are no longer firm they are limp. We say that they are flaccid and the plant will wilt.

If a lot of water leaves the cells then the cytoplasm starts to peel away from the cell wall. We say that the cell has undergone plasmolysis.