PLANT LAB
Part One: Tradescantia pallida
Background:
Leaves are the primary site of photosynthesis, and the chloroplasts are located in the cells of the palisade and spongy
mesophyll. Moisture is required for the gas exchange that is necessary for photosynthesis to take place. However, if
the mesophyll cells were left exposed to the environment the plant would suffer too much water loss. The waxy
cuticle provides a protective barrier against water loss. The cuticle also prevents adequate gas exchange. Therefore,
stomata are scattered across the surfaces of the leaf. These openings allow for gas exchange, but can also be routes
for water loss. The guard cells regulate gas exchange and water loss by changing shape so as to open or close
stomata. When the guard cells are turgid (full of water) they bend so as to keep the stomata open. When they are
flaccid (from lack of water) they close the stoma. Therefore, if plants are under water stress, the stomata close and
reduce further water loss. The purple Tradescantia pallida plant, commonly known as Wandering Jew has stomata
that are surrounded by chartreuse green guard cells on a field of bright fuchsia.
Materials:
 Microscope
 Microscope slide
 Cover slip


Leaves from a Tradescantia pallida –one kept in
light, one kept in the dark
Dropper
Procedure:
1. Take a small piece of a leaf from the Wandering Jew plant.
2. Place it on a drop of water on a slide.
3. Cover with a cover slip.
4. Place the slide on the stage of the microscope.
5. Locate the stomata at 40X.
6. Increase the magnification to 100X.
7. Record your observations and label the structures you see.
TOP of LEAF
BOTTOM of LEAF
Number of Stomata ______
Number of Stomata______
Magnification: ___ (eyepiece * objective)
Magnification: ___ (eyepiece * objective)
DAY: Stomata in the Tradescantia pallida plant
NIGHT: Stomata in the Tradescantia pallida plant
Magnification: ___ (eyepiece * objective)
Magnification: ___ (eyepiece * objective)
Analysis:
1. What is a stomata?
2. What is the function of stomata?
3. What causes the guard cells to swell or shrink?
4. What conditions would cause a plants stomata to open? Close?
5. Which surface of the leaf has stomatal pores? Why?
6. Were more stomata open in the leaf kept in the light or on the leaf kept in the dark? Why?
7. Research stomata in desert plants. What adaptations do desert plants have to regulate water balance and gas
exchange?
8. Research stomata in aquatic plants. What adaptations do aquatic plants have to regulate water balance and gas
exchange?
PART Two: Elodea
Background:
Movement of water molecules across a cell membrane from areas of low solute concentration to areas of high solute
concentration is called osmosis. This movement of water, in certain circumstances, can be harmful to cells. It can
result in severe cell water loss when living cells are placed into an environment where the solute concentration
outside the cell is much higher than inside the cell. This is called plasmolysis, and it can be seen under a microscope
when the cell contents pull away from the rigid cell wall as the water moves out. However, most cells live in an
environment where movement of water in and out of the cell is about equal and therefore there are no harmful
effects to the cell. In this lab, you will create an environment that causes plasmolysis in an Elodea (water plant) leaf.
Materials:
Microscope
Microscope slide
Cover slips
Beaker
Elodea (water plant)
Dropper
5% salt solution (2.5g solute in 50 ml H2O) … 1 group make this for the class & label it
10% salt solution (5g solute in 50 ml H2O) … Another group make this for the class & label it
Paper towel
Forceps
Procedure:
Elodea in distilled Water
1. Prepare a wet mount of an Elodea leaf with distilled water:
2. Place a drop of water in the middle of the slide.
3. Using forceps, remove a small leaf from the tip of an Elodea plant and lay it flat in the drop of water.
4. Cover with a cover slip.
5. Place the slide on the stage of the microscope.
6. Locate the cells at 40X.
7. Increase the magnification to 100X, then to 400X.
8. Record your observations in the Elodea Data Table. Be sure to label the cell wall, cytoplasm, and chloroplasts.
Also observe the movement of the chloroplasts (the green things inside each cell) – this movement is called
cytoplasmic streaming.
Elodea in 5% Salt Solution
1. Put the stage clips on your slide so it doesn’t move.
2. Focus on the cell
3. WITHOUT removing the slide from the stage of the microscope, Place 2drops of the 5% salt solution on the
slide at the left edge of the cover slip.
4. 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.
5. Continuously focus on the cell & watch what happens
6. Record your observations on the magnification of your choice. Include labels as above.
Elodea in 10% Salt Solution
1. Get a new piece of Elodea
2. Repeat the procedure above with 10% salt solution.
3. Record your observations. Include labels as above.
Flushing Out the Salt Solution (Rehydration)
1. WITHOUT removing the slide from the stage of the microscope, repeat the procedure with 3 drops of distilled
water.
2. Record your observations. Include labels.
Clean Up
1. Remove the slide from the stage, throw the leaf away, rinse off the slide and cover slip.
Elodea Data Table
Elodea in distilled Water
Magnification: ___ (eyepiece * objective)
Elodea in 10% Salt Water
Magnification: ___ (eyepiece * objective)
Elodea in 5% Salt Water
Magnification: ___ (eyepiece * objective)
Flushed Elodea in distilled Water
Magnification: ___ (eyepiece * objective)
Analysis:
1. Describe what happened to the Elodea cells in the presence of 5% salt solution.
2. Describe what happened to the Elodea cells in the presence of 10% salt solution.
3. Why didn't the salt from the outside just move inside the cell instead of the water moving out of the cell?
4. Explain how the cell plasmolysized without changing the shape of the cell as a whole.
5. Describe what happened when you flushed out the salt solution with distilled water.
6. From your observations, is plasmolysis reversible? Do you think this is concentration dependent? How could you
find out?
7. From your observations, is Elodea a freshwater or saltwater plant? Explain using the terms hypotonic, &
hypertonic.