Salt water causes water to leave onion cells through a process called osmosis.
Understanding Osmosis in Onion Cells
When onion cells are exposed to a salt water solution, the following occurs:
- The salt concentration outside the cell is higher than inside the cell.
- According to the provided reference, adding salt solution to the onion cells causes water to diffuse out of the cell (salt does not diffuse). Water leaves the cell, because the surrounding salt solution contains a lower concentration of water compared to the inside of the cell.
- Water moves from an area of high water concentration (inside the cell) to an area of low water concentration (the salt solution).
This process is a specific type of diffusion called osmosis, where water moves across a semi-permeable membrane (like the cell membrane) to equalize the concentration of water on both sides.
The Result: Plasmolysis
The movement of water out of the onion cell leads to a phenomenon called plasmolysis.
- The cell membrane shrinks and pulls away from the cell wall.
- The cell loses turgor pressure (the pressure of the cell contents against the cell wall).
- The onion cell becomes flaccid (limp).
Summary Table
| Condition | Water Concentration | Effect on Onion Cell |
|---|---|---|
| Inside Onion Cell | High | Water moves out |
| Surrounding Salt Water | Low | Receives water |
