Light Color and Elodea Oxygen Production

Medium

Does the color of light change how much oxygen an aquatic plant makes? Elodea is a water plant that releases oxygen during photosynthesis (the process plants use to turn light into food). You place elodea strands under five colors of light: - Red - Blue - Green - Yellow - White Each color is created by hanging colored cellophane in front of a lamp. You capture the oxygen in a graduated cylinder and measure it after 16 hours. Red and blue light each produced 1 mL of oxygen. White light matched that amount. Yellow produced half as much. Green produced no measurable oxygen at all.

Hypothesis

The hypothesis is that elodea will produce the most oxygen when living in blue light.

Science Concepts Learned

Chlorophyll

Chlorophyll is the green pigment in leaves that captures sunlight to make food for plants. You can test how light color affects this process by placing elodea under red, blue, green, yellow, and white cellophane filters hung in front of a lamp. After 16 hours, the results are striking: red and blue light each produced 1 mL of oxygen, while green produced no measurable oxygen at all.

Light Wavelength

Each color of light has a different wavelength, and plants respond to some wavelengths more than others. When elodea sits under red or blue cellophane, it produces 1 mL of oxygen, but green light yields no measurable oxygen at all. The wave size determines the color, and that color controls how much energy the plant can capture.

Dissolved Oxygen

Elodea is a water plant that releases oxygen during photosynthesis. That oxygen goes directly into the surrounding water, raising dissolved oxygen levels. In this experiment, you measure how much oxygen elodea produces under different colors of light.

Method & Materials

You will separate the elodea plants into five groups, each with a different color of light. You will measure the amount of oxygen produced by the elodea plants and record the results.

You will need a 250 ml beaker, a 25 ml graduated cylinder, a clamp, a ring stand, a large waterproof container, 10 strands of elodea, a light meter, four circles of colored cellophane, four hangers bent into circles, a lamp, a 60 watt light bulb, and tap water.

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Results

The results showed that the red, blue, and white light produced 1 ml of oxygen, while the yellow light produced 0.5 ml of oxygen. The green light produced no measurable amount of oxygen. This supports the hypothesis that elodea will produce the most oxygen when living in blue light.

Why do this project?

This science project is interesting because it can teach us how colors of light have different effects on photosynthesis.

Also Consider

Experiment variations to consider include testing the effects of different intensities of light or testing the effects of different lengths of time the light shines on the elodea plants.