Plasmolysis

Purpose:  How can a change in the environment affect the volume of the cytoplasm of cells? The purpose of this lab experiment is to demonstrate a biological principle observed in plant cells called plasmolysis.  Plasmolysis is the loss of water from the cell by osmosis, and this is evident when the cell contents pull away from the rigid cell wall as the water moves out. 

Materials:

• microscope
• clean slides and cover slips
• dropper
• salt
• spatula
• Elodea or an onion

Procedure:

1. Prepare a wet mount using a single leaf of Elodea or a thin onion section
2. Carefully add a few salt crystals to the edge of the cover slip. 
3. You may need to add a drop more water onto the crystals with the dropper. 
4. Now place the slide on the microscope stage and observe the leaf cells on low and then high power. 
5. As water moves out of the cells by osmosis, you should observe the cytoplasmic contents clumping away from the cell wall as shown in the diagram below.  Label the cell wall, central vacuole, cell membrane, and

cytoplasm on the cell shown below at left.

Conclusion:

1. In this experiment what is considered hypertonic?
2. What is considered hypotonic?
3. In the diagram above, the right cell is plasmolyzed.  The cell on the left is turgid.  What does this mean and under what conditions would it be in this state?
4. How could organisms such as algae be affected by an environment that is hypertonic because of chemicals released by a chemical company?