Download Lab 2:Turgor Pressure and Plant Cells

Name _________________________
Due Date: __________
Class Period: ______
Turgor Pressure and Plant Cells Lab
Introduction:
Turgor pressure is the pressure formed by water inside a plant cell. When plants have plenty of
water, their vacuoles are full and provide pressure. That combined with the cell walls allows a
plant to stand up tall even without a skeleton inside.
So what’s going on inside the cell when a plant doesn’t have enough water? We can cause water
to leave cells quickly by using the process of osmosis. Osmosis is the movement of water
through a membrane – water moves to make the concentrations of dissolved substances on both
sides of the membrane equal. (Adding water decreases concentration – like watering down some
kool-aid.)
Purpose: To find how salt solutions will affect the vacuole of a cell.
Hypothesis:
Materials
10% salt solution (10 gram salt in 100 ml water)
red onion
gloves (optional)
tweezers (optional)
distilled water
dropper
paper towels
slides and coverslip
colored pencils/phone
Procedure: Part 1
1. Obtain a wedge shaped piece of onion.
2. Use an eye dropper to place a drop of distilled water in the center of a microscope slide.
3. Break the onion and use the tweezers to peel a thin layer of skin tissue from the thick part
of the onion wedge and place it in the center of the microscope slide.
4. Add a drop of distilled water and a drop of iodine over the onion tissue on the slide.
5. Carefully lower a cover glass slip at an angle over the stained tissue, allowing air bubbles
to escape.
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Procedure: Part 2
6. Examine the prepared slide under the compound microscope at 100X magnification.
7. Draw the cells and identify the nucleus and cell wall.
8. Take a picture with your phone (optional)
ONION CELLS
Magnification: _____________
Procedure: Part 3
9. Use a dropper to add a few drops of the 10% salt solution to one side of the cover slip of
your prepared slide.
10. Fold a piece of paper towel to make it double. Carefully touch the paper to the opposite
side of the cover slip. This will pull the liquid under the coverslip and allow the salt
solution to come in. Repeat this 2-3 times.
11. Again examine the slide and draw and label what you see, especially what has changed.
ONION CELLS –
10% SALT SOLUTION ADDED
Magnification: _____________
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Procedure: Part 4
12. Now get rid of the salt water: use a dropper and add distilled water again. Use the paper
towel to draw out the salt solution, so that the water can replace it.
13. Again examine the slide and draw and label what you see. Add color if needed.
ONION CELLS WITH DISTILLED WATER AGAIN
Magnification: _____________
Conclusion:
1. How did the salt solution affect the cells? Describe what you saw and what caused this.
2. How did adding fresh water affect the cells? Describe what you saw and what caused this.
3. Relate this to a plant wilting or standing up. Why does a plant wilt when it needs water? Be
sure to explain what’s happening to the vacuole.
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