Download Plant Cell Turgor Lab Instructions

Plant Cell Turgor Pressure Lab
Botany
Introduction:
Plant cells differ from animal cells in a few significant ways apart from containing
chloroplasts that carry on photosynthesis. All plant cells have a rigid outer wall
structure around their cell. The cell wall provides structure, but prevents the plant
cells from being able to move freely. It’s like each cell is in a box and the boxes
cannot really move very much since they are stuck together in a supportive
structure. Plants, as organisms, are unable to move to obtain water. Since water is
not always in supply and may come in either too little or too great a quantity, plant
cells have adapted over time.
Plants store water in large vacuoles within their cells. The water pressure within
the vacuoles pushes with a force against the membrane and the wall of the cell.
This pressure causes the cell to become rigid and firm. This force is called turgor
pressure. The turgor pressure allows plant stems to stand upright and support other
structures such as leaves and flowers. If the plant cell vacuoles lose their water
content and the turgor pressure decreases, the plant as a whole wilts. If the water is
not replaced soon, the plant will die.
Learning Target: Observing Turgor Pressure
I Can… Utilize laboratory and critical thinking skills to determine what happens to
potato plant cells when they are exposed to air, placed in salt water, and placed in
fresh water.
I know I am successful when I am able to…
 Mass and calculate percent change of mass in the potatoes tested.
 Compare the results of the different potatoes/solutions.
 Analyze and infer what effect the different conditions have on the potato
cells.
 Identify how turgor pressure provides plants with support.
 Infer what plants may do to help regulate and maintain turgor pressure in
their cells
Materials:
 Potato slices (3)
o approximately the same size
 Cups (2)
 Plastic weighing dish (1)
 Distilled water (100 ml)
 Electronic balance (1)
 3.5% Saline solution (100 ml)
(salt water)
 Paper towels
 Graduated cylinder (1)
I) Procedure:
1.
You will work in groups of three students.
2.
Obtain three slices of potato from prep table (approximately the same size).
3.
Take the 2 cups and label them, using sharpie with the solution that will be
placed in each one, i.e. distilled water, salt water.
4.
Using the graduated cylinder, measure out 100 ml of distilled water into one
cup.
a. Be sure to measure the distilled water first to avoid cross
contamination.
5.
Using the graduated cylinder, measure out 100 ml of salt water into one cup.
II) Initial Measurements
6.
Dry off the three potato slices with a paper towel.
7.
Place the plastic dish on the balance and “zero” it (this will ignore the mass
of the dish in the measurement and only count the mass of the potato).
8.
Place one of the three dry potato slices on the plastic tray. Mass the potato
slice on the balance. Record this mass in column A of the data table in
grams.
a. Feel the flexibility of the slices of potato by gently flexing them. DO
NOT BREAK THEM. They should all feel firm and crisp. Record
initial flexibility of potato slice in column B of the data table.
9.
Repeat steps 7 & 8 for the other two potato slices.
Experiment
10. Place the first of your potato slices into the distilled water beaker. Place the
second potato slice into the saline solution. They should be submerged in the
solution.
11. Place the third on the plastic tray that you used while weighing.
12. Leave the potato slices in the solutions and air for 30 minutes.
While waiting for the potato slices to sit for 30 minutes, you will complete a
diagram of a typical plant cell and record your predictions about how the
solution will affect the water content in the plant cell vacuoles and overall turgor
pressure within each potato sample.
Final Measurements
13. After 30 minutes, carefully remove the air-exposed potato slice from the
plastic tray & pat it dry on a paper towel.
14. Measure & record the final mass of this slice in column C of the data sheet.
a. Follow the Initial Measurement steps 7 & 8.
15. Weigh and record the final mass of the other two slices (distilled water and
salt water) and record their mass in column C.
16. Gently flex each potato slice now and record the final flexibility of each in
column D.
17. Using a graduated cylinder, find the ending volume of the distilled water in
the beaker and record each in column F.
a. Repeat to find the final volume of the salt water.
18.Calculate the Percent Change in Mass (Column E) by following the formula
under the data table.
19. Throw the potato slices in the trash.
20. Clean up your equipment & area and return materials to their proper place.
a. Place glassware in the bussing tray to be washed.
b. Wipe down electronic balance.
c. Wipe down table
21. Create a graph from the data collected comparing the three potato samples.
22. Complete the analysis post lab questions.