## What magnification should be used for onion cells?

Place the slide under 40x magnifying lens and observe the onion cells.

What is plasmolysis in onion cells?

When concentrated sucrose solution, which has less water potential than onion cells, is added to the surrounding environment of epidermal red onion cells, plasmolysis occurs. During deplasmolysis, the protoplast within the cell swells to its original size as water is drawn into the cells.

What happened to the onion cells in the 20% saline solution?

It is possible to observe the plasmolysis of cells under the microscope. When salt water is added to onion cells, then the cells will lose water due to osmosis, this can be observed.

### What happens when onion cells are placed in a hypertonic solution?

When cells are bathed in a solution where the solute concentration is higher than in the cell cytoplasm (a hypertonic solution) the cell will lose water. In this practical you will observe osmosis in red onion epidermal cells.

How big is an onion cell in MM?

In the diagram to the right, the average size of each cell is 0.25mm.

How do you calculate Plasmolysis?

of plasmolysed cells (e. g. 39) divided by the Total No. of cells (e. g. 56). Then multiply this number by a 100 (e. g. 39 divided by 56 multiplied by a 100 = 69.64%). This would be the percentage of cells plasmolysed.

#### When you soaked the onion cells in saltwater explain what happened to them?

When the salt water is added to the onion tissue, over time students will notice that the cytoplasm pulls away from the cell wall as a result of water leaving the onion cell where it was more highly concentrated onto the slide where it was less concentrated.

How do you calculate the water potential of an onion cell?

The formula for calculating water potential is Ψ = ΨS + ΨP. Osmotic potential is directly proportional to the solute concentration. If the solute concentration of a solution increases, the potential for the water in that solution to undergo osmosis decreases.

How does plasmolysis take place in onion cells?

The process of plasmolysis takes place. The cytoplasm is separated from the cell wall as a result of water loss through osmosis. The appearance of onion cells submerged in solutions of NaCl of different concentrations suggest that the rate of plasmolysis is dependent on a concentration.

## How to see the effect of plasmolysis in flesh?

To see the effect of plasmolysis in the flesh, we used a one cell thick layer of red onion cells from the skin. Then added sucrose solution to one sample and nothing to the other samples. The results are below;

What is the role of sucrose in plasmolysis?

As the sucrose solution surrounds the cells, this provides the concentration gradient needed for water to move out of the cell. As the water moves out the cell, the cells loses its internal pressure and the cell membrane starts to move away from the cell wall, plasmolysis is occurring.

Did You Know you can reverse plasmolysis with distilled water?

Did you know that If you put distilled water onto the plasmolysed onion cells you can reverse the plasmolysis and change them back to normal turgid onion cells. (As long as you do it fairly quickly).