How Light Affects Seed Germination

When a seed that has been planted starts to sprout, it is called germination. Different seeds require different conditions to germinate, but they all need three things: light, heat, and water. In this experiment we’ll investigate how light affects the germination of bean seeds.


3 clear CD cases, with the plastic piece that holds the CD removed
Potting soil or seed starter
Small pail
Clear tape
1 package of bean seeds (pinto or lima beans work well)
A piece of thin, see through cloth such as cheese cloth
A piece of dark colored cloth or a small cardboard box
An eyedropper or small squeeze bottle like eye drops come in (wash it thoroughly first)


Place a few handfuls of soil or seed starter into the pail.
Add enough water to make sure that the soil is moist.
Open the CD cases with the hinge to the side so that the small openings in the case are on the top and bottom. Add a small amount of soil to each case. Make sure to fill the cases only half way so that your seed has room to grow.
Place your seed in the middle of the soil with the small dot facing downward. The bean should be positioned so that it is in the shape of a frown rather than a smile. You may want to plant two seeds to make sure at least one germinates.
Add a few more drops of water onto the seed.
Close the CD case and use the clear tape to secure the bottom and sides. Make sure to leave the top openings uncovered so you can water your seeds.
Place the cases in a warm area of the house and leave one case uncovered.
Cover the second case with cheese cloth or other material that will let some light through.
Cover the third case with the dark material or place it in the cardboard box. (make sure all the cases are standing upright with the bottom of the seed facing downward)
Use the eyedropper or squeeze bottle to water your seeds each day, giving each seed the same amount.
Check the seeds each day to see if they have germinated and record the results in a notebook.

You should see that the seed in the uncovered case will germinate first, followed by the one with the see through cloth. The seed that doesn’t get any light should take the longest to germinate.

If you want to continue your experiment to see how light affects plant growth, leave the seeds where they are and continue watering them. As they grow, you’ll notice a big difference in the growth rate of the three plants as well as in their color.

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