1. Dissolved substances (inside a plant cell) = contribute to solute potential (ψs).
2. More solute molecules present --> the lower is the water potential (ψ).
3. When water pontential is lower than> external solution:
- water molecules move into the cell .
- pressure inside the cell increases
- sell contents press against the cell wall
- create a pressure potential (ψs).
4. Water potential (of a plant cell) = solute potential + pressure potential.
5. Water potential = free energy of water.
6. By convention, water potential of pure water = 0 megapascal (MPa).
7. Water will move:
- from a region of higher (less -ve) water potential
- to a region of lower (more -ve) water potential.
8. In plasmolysed cell:
- pressure potential = zero
- water potential = solute potential.
9. As more water molecules enter a cell
- pressure potential ↑ increases
- so is its water potential ↑
- cell becomes turgid.
- less and less water molecules enter the cell.
10. Most minerals
- are actively transported into the root.
- there is a gradient of successfully
- lower water potentials from root hair to the xylem vessels
- result in water uptake by osmosis is enhanced.
11. Water moves by osmosis in the roots follows three pathways:
- apoplast
- symplast
- vacuole.
12. Apoplastic pathway:
- water travels along the cell wall
- and extracelular spaces.
 |
| Apoplast pathway |
13. Symplastic pathway:
- water moves across the cytoplasm of one cell to the next
- across the plasma membrane
- through the plasmodesmata.
 |
| Symplast pathway |
14. Vacuole pathway:
- water moves from vacuole to vacuole of one cell to the next
- across the plasma membrane
- through the plasmodesmata.
 |
| Vacuole pathway |
No comments:
Post a Comment