3.3.3: movement of water through plants Flashcards
Why can water pass through a cell wall?
Because the cellulose cell walls of a plant cell are fully permeable to water. Water molecules can move freely between the cellulose molecules.
What are plasmodesmata?
Gaps in the call wall containing cytoplasm that connects two cells.
What are the three possible pathways that water can take through a plant?
The apoplast, symplast and vacuolar pathways.
Describe the apoplast pathway.
- Water passes through the spaces in the cell walls and in between the cells. It does not pass through any plasma membranes into the cells.
- This means that water moves by mass flow rather than osmosis.
- Also, dissolved mineral ions and salts can be carried with water.
Describe the symplast pathway.
Water enters the call cytoplasm through the plasma membrane It can then pass through the plasmodesmata from one cell to the next.
Describe the vacuolar pathway.
The water passes through the cytoplasm of the cells and is also able to enter and pass through the vacuoles as well.
What is water potential a measure of?
The tendency of water to move from one place to another. Water always moves from an area of high water potential to an area of low water potential.
Why is the water potential of a plant cell always negative?
Because the water potential of pure water is zero an the cytoplasm contains mineral ions and sugars (solutes) which reduce the water potential. This is because there are fewer ‘free’ water molecules available.
What happens to a plant cell when you put it in pure water?
It will tale up water molecules by osmosis because the water molecules move down the water potential gradient from a region of high to low water potential.
Why will the cell not continue to absorb water until it bursts?
Because it has a strong cellulose cell wall.
What is a cell full of water described as?
Turgid.
What is pressure potential?
The water inside starts to exert pressure on the wall called pressure potential. As the pressure potential builds up, it reduces the influx of water.
What will happen to a plant cell placed in salt solution with a very negative (low) water potential.
The plant cell will lose water by osmosis. Water will move from a high to low water potential out of the cell. As water loss continues, the cytoplasm and the vacuole shrinks. Eventually, the cytoplasm no longer pushes against the cell wall and the cell is no longer turgid.
What is the plant cell called if water continues to leave the cell?
The plasma membrane will lose contact with with the wall- a condition known as plasmolysis. The tissue is now flaccid.
Describe water movement between two cells that are next to each other.
Water molecules can pass from one cell to another. The water molecules will move from a high to low water potential by osmosis.
