BioLab 4 - Plasmolysis

The purpose of this activity is to investigate the effects of a hypertonic solution on the cells of the red onion.

MATERIALS: red onion epidermis, forceps, dropper, distilled water, 5% sodium chloride (table salt) solution, paper towels, microscope, glass slide, and cover slip.

PROCEDURE:

1. Make a wet mount of the red onion epidermis.
    
2. Examine under low power with the microscope. When you have a clear view of several cells, switch to medium power lens. Make a colored drawing, properly labeled in the circle below.
   

3. Place one drop of the salt solution at the edge of your cover slip while placing a small piece of paper towel along the opposite edge of the cover slip. The paper should draw out the water and draw in the salt solution.
    
4. Make sure that the salt solution has time to diffuse under the cover slip.
    
5. Observe the affects of the solution on the onion cells. Make a properly labeled, colored drawing of the cells' appearance in the circle below.
   

6. Replace the sodium chloride solution with distilled water and add it in the same way that the salt solution was added. Make a properly labeled, colored drawing of the cells' appearance in the circle below.

QUESTIONS:

1. Which of the two liquids was hypotonic to the cells?

2. On what evidence do you base this?

3. Which of the two liquids was hypertonic to the cells?

 
4. On what evidence do you base this?