Movement of water through plants 3.3.3 Flashcards
How do water molecules move between cells?
They move freely between the cellulose molecules & in gaps between cells, as cellulose is permeable in water.
It can also pass through the partially permeable plasma membrane
Cells are also connected via cytoplasmic bridges, and these junctions are called plasmodesmata
What are the 3 possible water pathways in a plant?
- Apoplast pathway
- Symplast pathway
- Vacuolar pathway
What is the apoplast pathway?
Water passes through spaces in the cell walls and between the cells, it does not pass through any plasma membranes into the cells
How does water move through the apoplast pathway?
By mass flow (diffusion) not osmosis
Why does the apoplast pathway become blocked?
Due to a waxy band of suberin at the endodermis, known as the Casparian strip - which causes the water to take the symplast pathway.
What is the symplast pathway?
Water enters the cell cytoplasm through the plasma membrane, and water passes through the plasmodesmata from one cell to the next.
What is the vacuolar pathway?
It is similar to the symplast pathway, but the water also enters and passes through the vacuoles
Why is water potential in plant cells always negative?
Due to the mineral ions and sugars dissolved with the cytoplasm.
What happens if you place a plant cell in pure water?
It will take up water molecules by osmosis, and they will move down the water potential gradient.
What happens in the cell wall once the cell becomes turgid
The cellulose in the cell wall prevents the uptake of water and the cell from bursting.
What happens to water uptake as pressure potential increases?
It decreases
What happens if you place a plant cell in a solution with a very negative water potential?
It will lose water via osmosis, due to the water potential being higher in the cell than the solution.
This will cause the cell to become flaccid, and if the plasma membrane loses contact with the cell wall the cell will become plasmolysed.
How does water move from cell to cell (direction)?
From the cell with the less negative water potential to the cell with the more negative water potential.
