Osmosis in Plant Cells ­

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.