Osmosis in plant cells
Plant cells in a hypotonic solution
- Cells have a lower water potential than the external solution.
- Cells gain water by osmosis.
- The vacuole and cytoplasm increase in volume.
- The cell membrane is pushed harder against the cell wall causing it to stretch a little.
- The plant cell becomes stiffer (turgid) - it doesn’t burst because it has a cell wall.
- Turgor is the pressure of the swollen cell contents against the cell wall.
- Turgor is important in it supports the non-woody parts of the plant.
- Without turgor the plant will wilt. The stoma in the plant opens when the plant is turgid so to let out excess water.
Plant cells in a hypertonic solution
- Cells have a higher water potential than the external solution.
- Cells lose water by osmosis.
- The vacuole and cytoplasm decrease in volume.
- Shrinkage stops when the cell sap is at the same concentration as the external solution.
- The stoma closes so not to let out any water.
- The plant tissues become flaccid, it has shrunk slightly.
- May go on to become plasmolysed if there is a large difference in water potential.
- In plasmolysis the cell membrane pulls away from the cell wall.