Plasmolysis/Osmosis in Elodea Plant Cells
Scientific Question: What effect will salt water have on
elodea plant cells?
INTRODUCTION
Review the background and procedure for the lab below. Then
record your data and observations, and answer the questions at
the end of the page in your lab notebook.
Background Information:
 When plant cells are surrounded with salt water, the water inside the plant moves from where there is more water
(less salt) through the cell wall and membrane to the outside where there is less water (more salt). This process of
water movement from a high concentration of water to a lesser concentration of water is called osmosis.
 When the water movement is out from a cell, we call this osmosis or more specifically, Plasmolysis/Osmosis/Osmosis.
 Plasmolysis/Osmosis is the shrinking of the cytoplasm of a plant cell in response to diffusion of water out of the cell
and into a high salt concentration solution.
 During Plasmolysis /Osmosis, the cell membrane pulls away from the cell wall. This does not happen in low salt
concentration because of the rigid cell wall. Plant cells maintain their normal size and shape in a low salt concentration
solution.
 Plasmolysis/Osmosis/Osmosis is a reversible process
Design
Independent Variable
What will you be testing?
Dependent Variable
What will you be measuring?
Constants
What will stay the same in your experiment?
Hypothesis
Create a testable statement in response the question
stated above.
Procedure
Elodea in Tap Water
1. Prepare a wet mount of an Elodea leaf with tap water. To do this, place a drop of water towards one end of the slide.
Using forceps, remove a small leaf from the tip of an Elodea plant and lay it flat in the drop of water. Cover with a cover
slip.
2. Observe the leaf at 40X and record your observations.
3. Increase the magnification to 100X, observe, and record your observations.
Elodea in 5% Salt Solution
1. Remove the slide from the stage of the microscope.
2. Place 2 drops of the 5% salt solution on the slide at the
left edge of the cover slip.
3. Tear off a small piece of paper towel and place the torn
edge on the slide at the right edge of the cover slip. The
piece of towel should begin to soak up water, drawing the
salt solution under the cover slip as it does so. (See
Figure)
4. Return the slide to the microscope stage and observe the cells at 40X and 100X.
5. Record your observations.
Elodea in 10% Salt Solution
1. Repeat the procedure above with 10% salt solution.
2. Observe the cells at 40X and 100X. Record your observations.
Flushing Out the Salt Solution
1. Remove the slide from the stage of the microscope.
2. Place 3-5 drops of tap water on the slide at the cover slip.
3. Draw the water through using a small piece of paper towel.
4. Observe the cells at 40x and 100x. Record your observations.
5. Remove the slide from the stage, clean it, and the cover slip, and put it away.
6. Remove the slide from the stage, clean it, and the cover slip, and put it away.
Observations
1. Prepare sketches of a group of Elodea cells under each set of conditions (tap water, 5% salt solution, and 10% salt
solution).
2. Draw the magnification under which the plant cells are being observed (40x or 100x).
3. Label the sketches to note the cell structures (cell wall/cell membrane) that you can identify.
4. Be sure to note any changes in the color, size, and shape of the cells.
5. Make your sketches as accurate as possible.
Freshwater Observations
40X Drawing
100X Drawing
5% Salt Water Observations
40X Drawing
100X Drawing
10% Salt Water Observations
40X Drawing
100X Drawing
Conclusions (Attach answers on another paper)
1. What happens to the cells as the salt water flows under the cover slip?
2. What happens to the cells when the salt water is flushed out with fresh water?
3. Why did the water in pass out of the cell?
4. Why do you think the outer boundary of the cell DID NOT collapse?