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NAME ________________________________
LAB
CYCLOSIS (Cytoplasmic Streaming) IN ELODEA
INTRODUCTION
Green plant cells contain special structures called chloroplasts
(p. 65). Chloroplasts are cytoplasmic organelles that function
in manufacturing/synthesizing plant food (i.e., glucose).
Chloroplasts are green because they contain the green pigment
chlorophyll. This pigment has an important job of absorbing
sunlight energy during a complex chemical process called
photosynthesis. Photosynthesis entails capturing and
transforming the energy of sunlight into chemical energy.
This chemical energy is found in the chemical bonds of glucose.
Elodea is a leafy flowering plant commonly found in aquariums. Its leaves are thin and
transparent; most of them are only 2 cell layers thick. New leaves are produced at the tip of
the plant. You will examine one or more of these thin leaves in this laboratory investigation.
MATERIALS

Compound light microscope, slides, coverslips, methylene blue, Elodea leaf
METHODS
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Tear an Elodea leaf in half.
Prepare a slide of one of the leaf portions. DO NOT ADD WATER (i.e., no wet mount).
Examine the cells under both LOW & HIGH power.
Observations: Note the shape of the cells, the presence of cell walls, and the shape &
location of the chloroplasts.
Sketch the cells under LOW & HIGH power. Label the cell wall & chloroplasts.
Determine the size of an individual cell. Assume HIGH power FOV is 300 µm.
Observations: Examine the cells carefully for any occurrence of cyclosis (or cytoplasmic
streaming). Cyclosis is the movement of the cytoplasm. Try to find cells where the
chloroplasts are moving. This is an indication that the cytoplasm is moving.
Remove the wet mount slide from the stage. Stain the Elodea cells by placing ONE drop of
methylene blue at one edge of the coverslip. Draw it under the coverslip by placing a piece
of paper towel to the opposite edge.
Observe the cells again under LOW & HIGH power to see if any additional structures are
visible. Sketch the stained cells under HIGH power. Label the cell wall, chloroplasts, cell
membrane (if visible), nucleus, nucleolus, and the large vacuole (if visible).
RESULTS
 Observations
 Estimated cell size (in µm)
 3 sketches – 1 under LOW & 2 under HIGH power. LABEL the stained HIGH power sketch.
 Shape of Elodea cells? __________________________
 Cell wall present…Yes or No? _______
Shape of chloroplasts? _________________
 Location of chloroplasts? __________________
 Did you observe cyclosis…Yes or No? _______
 If yes, where were the chloroplasts moving? _________________________________
 Estimated size of a single Elodea cell? ________ µm
ELODEA CELLS
LOW
(unstained)
HIGH
(unstained)
HIGH
(stained)
DISCUSSION
1. What is cyclosis AND why is it important to cells?
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------2. If you were to focus up and down on one particular cell (using the fine adjustment knob),
why would some chloroplasts come into view while others would go out of view?
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------3. What role do chloroplasts play during photosynthesis?
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------4. Why would it be advantageous to have Elodea in a balanced aquarium?
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------5. What additional structure could be seen after the cells were stained with methylene blue?
----------------------------------------------------------------------------------------------------------------------6. Why do you think the chloroplasts moved only around the edges of the cells?
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------7. Most plants store their excess glucose as one of two possible polysaccharides. One is
cellulose, a key component of their cells walls. What is the other & where is it located?
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