In plants: When placed in hypertonic solution (Lower water potential), like conc. salt solution, water moves out of the cell and the vacuole shrinks, drawing the cytoplasm and cell membrane towards the centre. The cell is said to be flaccid and plasmolyzed, and overall, the plant tissue feels soft. (Note: The cell wall is FULLY permeable) The process can be reversed.
When placed in a hypotonic solution, with higher water potential, like distilled water, water moves in instead of moving out: The vacuole expands and pushes against the cell wall, making the cell turgid and appear hard. The tissue may be bent as cells press against one another.
In Animals:
As the animal cells lack a cell wall, osmosis can cause destruction in cells:
When placed in hypertonic solution, water moves out and the cell shrinks dramatically, and becomes crenated where the cell membrane becomes (spikes). The cell can no longer function.
When placed in a hypotonic solution, water moves in and teh cell expands to such an extent that it bursts! OMG! The cell is now haemolyses. The cell "ghost" is the plams membrane left behind as the cell contents burst out.
Animals use this mechanism to regulate excretion: As essential ions are reabsorbed into the body ion the kidneys, water is also reabsorbed to prevent excess water loss via urine. However, the water potential gradient is built between body fluids and not cells, not no cells are harmed: how wonderful!
Decreasing water potential from left to right:
Haemolyses Crenated
Isotonic = same water potential
