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Internet Biolab
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Unit 3: The Life of a Cell
Chapter 9: Energy in a Cell  
Internet Biolab
What Factors Influence Photosynthesis?
Oxygen is one of the products of photosynthesis. Because oxygen is only slightly soluble in water, aquatic plants such as Elodea give off visible bubbles of oxygen as they carry out photosynthesis. By measuring the rate at which bubbles form, you can measure the rate of photosynthesis.
Preparation
Problem
How do different wavelengths of light a plant receives affect its rate of photosynthesis?

Objectives
In this BioLab, you will:

  • Observe photosynthesis in an aquatic organism.
  • Measure the rate of photosynthesis.
  • Research the wavelengths of various colors of light.
  • Observe how various wavelengths of light influence the rate of photosynthesis.
  • Use the Internet to collect and compare data from other students.
Materials
  • 1000-mL beaker
  • Three Elodea plants
  • String
  • Washers
  • Colored cellophane, assorted colors
  • Lamp with reflector and 150-watt bulb
  • 0.25% sodium hydrogen carbonate (baking soda) solution
  • Watch with second hand
Data Sources

Safety Precautions
CAUTION: Always wear goggles in the lab.

Skill Handbook
If you need help with this lab, refer to the Skill Handbook.

Procedure
1. Construct a basic setup like the one shown in your textbook on page 238.

2. Create a data table to record your measurements. Be sure to include a column for each color of light you will investigate and a column for the control experiment.

3. Place the Elodea plants in the beaker, then completely cover the plants with water. Add some of the baking soda solution. The solution provides CO2 for the aquarium plants. Be sure to use the same amount of water and solution for each trial.

4. Conduct a control experiment by directing the lamp (without colored cellophane) on the plant and notice when you see the bubbles.

5. Observe and record the number of oxygen bubbles that Elodea generates in five minutes.

6. Cover the lamp with a piece of colored cellophane and repeat steps 4 and 5.

7. Repeat steps 4 and 5 with a different color of cellophane.

8. Post your data below.

9. Return plant material to an aquarium to prevent it from drying out.

Post Your Data
Control
Indicate
Color 1
Color 1
Indicate
Color 2
Color 2
Bubbles observed
in 5 minutes
*City
*State
*School

*Required field
Analyze and Conclude
1. Interpreting Observations From where did the bubbles of oxygen emerge? Why?

2. Making Inferences Explain how counting bubbles measures the rate of photosynthesis.

3. Using the Internet Look up the wavelengths of the colors of light you used. Make a graph of your data and

data posted by other students with the rate of photosynthesis per minute plotted against the wavelength of light you tested for both the control and experimental setups. Write a sentence or two explaining the graph.

4. Error Analysis Why was it important to use the same amount of sodium hydrogen carbonate in each trial?