How Light Affects Plant Growth

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Updated on Feb 24, 2014

Purpose: The purpose of this project is to show that different colors of light affect the development of plants.

Hypothesis: I predict that plants will grow better under blue, red and yellow lights than they will under white and green lights.

Background: The relationship between light and plant growth can be demonstrated by exposing leaves to various colors of light. Light supplies the power to carry on photosynthesis, the food-making process in leaves. But the spectrum of light most utilized by a leaf is limited to three distinct colors, red, blue and yellow. For example, leaves appear green because green is the color most leaves reflect rather than absorb and use.

Independent Variable: Color of light

Dependent Variable: Plant height

Control Variables: Same size soybean plants, fertilizer, soil, water, potting soil, colored filters, 10 gallon aquarium tank.

Procedures: Plant four soybean plants of the same size in an aquarium containing 5" of well moistened potting soil. Apply the recommended dosage of fertilizer. Place a colored filter tent over each plant. One filter should be clear. Use blue, yellow, and red film for the other filters. Place the aquarium in direct sunlight. Keep in the same location during the experiment and water daily. Measure each plant every day and record your findings in a notebook. Be sure to measure from the bottom of the aquarium and not the surface of the potting soil.

Materials: All the materials for this project are available locally. You can obtain a 10 gallon aquarium from a pet shop. Office stores sell colored transparency sheets. Most garden supply shops sell soybean seeds, potting soil and plant feretilizer. Be sure to germinate your soybean plants to a height of 4" before beginning your experiment.

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