Photosynthesis in Elodea
Problem: Is photosynthesis taking place in the aquatic plant Elodea?
Elodea is a common “exotic” aquarium plant that has also escaped into some local waterways. Elodea is an excellent plant for our studies of photosynthesis and cells because it is easy to grow, and readily available. The leaves are only a few cells thick so they will be easy for us to observe under the microscope to look at cells and cell parts.
Recall from the reading that photosynthesis requires certain raw materials and produces certain products, one of which is released by the cells as a gas. You have read about the process of photosynthesis, and now you will act as any scientist would and ask to see the proof! How can you see the proof however, since gases are colorless and oxygen and carbon dioxide are both odorless too? Read the Procedure at this point.
Book Reference: pages 88-90 (pages 94 – 96 in the new light green version)
Pre-lab Questions: (Read Procedure before answering.)
Materials: (per group)
Sprig of Elodea
Distilled Water w /Baking Soda
Graduated Cylinder or Test Tube
Timer or Watch
60 watt Spotlight
Before you begin, create a data table.
Clean-up all materials as your instructor directs.
Post-Lab Questions: (Answer each in a 1-paragraph answer.)
1. Is Photosynthesis taking place in Elodea? Use evidence from your investigation to support your answer.
2. Consider these
- The light we are using is white and thus contains all the colors of the rainbow.
- When each color of light reaches an object, the light energy is either absorbed into the object or reflected back out.
color of an object is actually the color of the light that is reflected back
3. Using this investigation as a basis, design an experiment to test the effect of an environmental factor on the rate of photosynthesis. Some possible independent variables include: distance from light, different light intensities (wattages), different colors, or temperature.
4. Bonus: Why
did we use the baking soda?
(In your conclusion, you should briefly summarize the problem and what you did. Then answer the problem referring to the data and background information including your pre and post lab questions).