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Tricked: How Does the Absence of Light Affect Bean Seedlings? (page 2)

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Author: Janice VanCleave

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How much light is needed to prevent etiolation? Repeat the experiment, cutting a 2-inch (5-cm)-square opening in the top of the closed box. Cover the hole with a piece of black paper. At the same time each day during the test period, lift the paper cover from the hole and allow light to enter the box for 5 minutes. Further test the quantity of light needed to prevent etiolation by using larger or smaller holes in the box and by increasing or decreasing the amount of time the light enters the box. Science Fair Hint: Make bar graphs of the growth of each plant to use as part of a project display.

Tricked

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Does the color of the light affect growth? Obtain dark-colored cellophane in as many colors as possible. NOTE: Use several layers of light-colored cellophane to produce a darker color. Use clear cellophane as a control. Follow the procedure in the original experiment to plant seeds in paper cups. Prepare 1 cup for each color of cellophane used, including clear. Loosely cover each cup with cellophane, taping the edges and top of the cellophane together to form a tubelike "hat" over the cup.

Depending on the intensity of the color, the color of the cellophane will be received by the plant. Clear cellophane allows all the colors in white light to be received by the plant. Compare your results to determine how certain colors affect the bean plants' growth.

Check It Out!

The plant seems to "know" whether it is in light or in darkness. Find out more about a plant's responses to light. How do day and night length affect a plant? What is a phytochrome?

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