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Experiment 5
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Does Colored Mulch Affect the Growth Rate of a Plant?
Experiment 5

Purpose: To determine if colored plastic (mulch) will affect the stem length of plants.

Materials: 8 pots; 8 bean seeds; colored plastic in red, black, and white; ruler; water; toothpicks; greenhouse or window that receives full sun; tape; potting soil; pencil; small cup.
cartoon drawing of a scientist working with flask and microscope

Procedure: Fill pots with equal amounts of potting soil. Make a hole about 2 cm long in each pot using a pencil, and place 1 seed in each pot. Cover seed with loose soil. Mark where you planted the seed with a toothpick. Cut plastic in pieces large enough to cover each pot. Cut a smaller hole in the center of the plastic and cover pot with the plastic. Be sure the smaller hole in the center is where your toothpick is so the seed is exposed to light. Take the toothpicks out after you have taped the plastic to the pot. Do this twice for each of the colors. You will have 2 red, 2 black, 2 white, and 2 uncovered. After the seeds have emerged through the soil (about 5 days), take stem measurements. Measure the stems in each pot for 14 days. Do not forget to water your plants during the experiment. About every other day, use a small cup and pour a small amount of water in each hole where the plant is growing. Note the differences in height among the plants grown over different colored plastic.

Think About This:

image of many question marks

1. Which plastic helped produce the longest stem length?

2. Which plant had the shortest stem length?

3. What do you think this tells us about how a plant uses reflected light?

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