Part 3: Osmosis in Living Plant Cells
Introduction
In this lab, you will microscopically observe an Elodea densa plant leaf and explore the effects of
different solution concentrations on the cells. You will then use the solutions to determine the
water potential of plant tissues, such as white or sweet potato tubers.
Materials List
1 Thermometer
1 Graduated cylinder
6 Plastic cups
150 mL Red mystery solution
150 mL Orange mystery solution
150 mL Yellow mystery solution
150 mL Green mystery solution
150 mL Blue mystery solution
175 mL Distilled water
1 Microscope slide
5 Paper towels
1 Pair of forceps
1 Compound microscope
1 Scalpel
1 Coverslip
6 Potato tubers
1 Balance
1 Ruler
Part 3A – Procedure: Structured Inquiry
1. Using the forceps, remove an Elodea densa leaf from its stem and place it gently on a
clean microscope slide.
2. Add two to three drops of distilled water to the slide and cover with a coverslip.
3. Examine the cell at 40X magnification and note the characteristics of the cells. In your lab
notebook, draw several cells that show a good representation of the cells you observed. In
your drawing, label all visible structures and organelles.
4. Remove the microscope slide. Choose one of the solutions from Part 2 of this lab
(albumin, glucose, sucrose, NaCl solution). Add two to three drops of this solution across
the leaf sample.
5. Allow the slide to sit for two to three minutes in the solution and re-examine the sample
under the microscope.

To speed up the reaction to the cells in solution, place a paper towel on the opposite
end of the coverslip to wick your solution through the cells.
6. Note the appearance of the cells. In your lab notebook, draw several cells that show a
good representation of the cells you observed. In your drawing, label all visible structures
and organelles.
Label all visible structures and organelles in your drawings.
Part 3B– Procedure: Open Inquiry
Given potato cores, gummy bears, a balance, metric ruler, and 5 mystery solutions of sucrose,
design an experiment to the concentrations of the mystery solutions. Spend the first day
planning out your experimental design and get it approved by Ms. Sauer. On the second day,
implement your experiment to determine the concentration of the mystery solutions. You can
use all of the available materials, or just some.
Use the following steps when designing your experiment.
1. Define the question or testable hypothesis.
2. Describe the background information. Include previous experiments.
3. Describe the experimental design with controls, variables, and observations.
4. Describe the possible results and how they would be interpreted.
5. List the materials and methods to be used.
6. Note potential safety issues.
After the plan is approved by your teacher:
7. The step-by-step procedure should be documented in the lab notebook. This includes
recording the calculations of concentrations, etc. as well as the actual weights and volumes
used.
8. The results should be recorded (including drawings, photos, data print outs).
9. The analysis of results should be recorded.
10. Draw conclusions based on how the results compared to the predictions.
11. Limitations of the conclusions should be discussed, including thoughts about improving
the experimental design, statistical significance and uncontrolled variables.
12. Further study direction should be considered.
Part 3B– Assessment
1. Which color mystery solution had the highest concentration of sucrose? How do you
know this?
2. Knowing that the mystery solutions were sucrose at concentrations of 0.2 M, 0.4 M, 0.6 M,
0.8 M, and 1.0 M, calculate the water potential of the potato core. Show your calculations
and explain your reasoning.
3. If you looked at your potato cores under the microscope, describe what you think you
would see.