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by Robert A Furtado |
Instructor's Objectives
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Students will be able to:
a. Prepare successful wet
mount slide of Elodea.
b. Identify cytoplasmic streaming
c. Determine and identify environmental conditions that induce cytoplasmic streaming.
d. Determine the positive aspects of cytoplasmic streaming.
e. Work in cooperative groups.
f. Illustrate knowledge
and use of the scientific method.
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Standard microscope, slides, coverslps, thermometer, pH
meter, acetic acid, baking soda,
various strength salt solutions (.85%,1%,2%), magnets, light
source
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1. Students have adequate skills with using a microscope.
2. They should know how to focus a microscope as well as create a wet
mount slide of a specimen.
3. Should have knowledge of cell organelle structure.
The cytoplasm of most plant cells is constantly
in motion. This streaming movement is called cyclosis due to its circular
path. Cytoplasmic streaming apparently enhances the exchange of materials
between organelles, as well as between cells. It is thought that microfilaments
(actin filaments) of the cells' cytoskeleton provide the driving force
for cytoplasmic streaming and control the direction of the cytoplasmic
movements as well. It has been recorded in the literature that cytoplasmic
streaming is related directly to levels of absorbed ultraviolet radiation.
The plants that are being used in the lab investigation have been exposed
to sunlight for several hours to enhance the cytoplasmic streaming.
2. Add a drop of water to the center of your slide.
3. Remove a leaf from the Anachris at your station.
4. Add the leaf to the drop of water.
5. Place the coverslip on the leaf sample at
a 45 degree angle. Allow the coverslip
to slowly fall onto
the sample. (reduces air bubble contamination)
6. Make a diagram of the Elodea under low power magnification.
7. Look for cytoplasmic streaming.
8. With a second diagram illustrate direction
of cytoplasmic streaming.
9. Determine the size of the Elodea cell in microns.
10. Determine the speed of the cytoplasmic streaming in microns/sec.
11. Record the environmental conditions of the Elodea environment.
Procedure B:
1. Develop a procedure to change the environmental
conditions of the Elodea.
2. Record the changes you have made to that environment.
3. Wait ten minutes. Then follow procedure A #2,3, 4,5,6,7,8,10.
4. Make a diagram of the Elodea and its cytoplasmic
streaming under the new
environmental conditions.
Procedure C:
The changes you made for Procedure B
you now want to replicate for Procedure C.
A sprig of Elodea shall be placed
into a test tube with the changed water conditions.
This time you will wait 24 hours before
recording results of streaming.
Evaluation technique will be a rubric as well as review of the questions students have answered.
1. Why are the streaming
cytoplasm and the chloroplasts restricted to the periphery of most
mature plant cells?
2. Calculate the speed of
the chloroplast if it were increased to the size of your body!
A. Extension Questions
1. Calculate the distance
traveled by the chloroplast over a day, etc.
2. Compare the size
of the chloroplast in the image. Construct a graph of size distribution.
Is size influenced by velocity?
B. Extension Experiment
1.
El Rancho Elodea
2. Magnetic impact upon
cytoplasmic streaming.