Why onion cells plasmolyze

Therefore, there is no net movement of water. If a cell is in a hypertonic environment one in which the environmental concentration of solute is greater than the solute concentration within the cell , then water will move out of the cell. In this experiment, you will expose living cells to a hypertonic solution and observe the results. Prepare a wet mount and view the slide under low power - sketch a few cells for comparison later. Add a few drops of the prepared salt solution to one edge of the coverslip and use a small piece of paper towel against the other edge to draw the solution across the sample.

Once the paper towel is saturated, it can be removed. This is also a common staining procedure. Spend a few minutes observing the cells. Compare the cells with your sketch and note any changes. If you added enough salt solution, you should see that the cytoplasm and cell membranes have pulled away from the cell walls. This process is known as plasmolysis and only occurs in plant cells. See note 2. Cover it with a drop or two of distilled water. Add a cover slip. Replace it with distilled water added at the other side of the coverslip.

This experiment could be run as a qualitative investigation of the effects of water and sodium chloride solution on the contents of plant cells. You can make the investigation quantitative by using different concentrations of sodium chloride solution e. Students can count how many of a fixed number of cells are plasmolysed at each concentration.

You can calculate the percentage of plasmolysed cells and plot a graph of percentage plasmolysis against sodium chloride concentration. Cells are plasmolysed plasmolysis has occurred when the cell contents shrink and come away from the cell wall.

The student sheet introduces the word, but does not require them to use it, so you do not need to explain this term unless it is relevant to your students. Download the student sheet Observing osmosis, plasmolysis and turgor in plant cells KB with questions and answers. Investigating the effect of concentration of blackcurrant squash on osmosis in chipped potatoes. Search Search. You are here: Practical Biology Exchange of materials Osmosis Observing osmosis, plasmolysis and turgor in plant cells.

Lesson organisation This activity could be carried out by students working as individuals or in pairs, depending on the number of microscopes available.