Answer: I've done similar classroom presentations and have always used either bean seeds or corn seeds. Both germinate quickly (4-7 days) and both show evidence of light deprivation very quickly. Here's one experiment:
Are Seedlings Afraid of the Dark?
Purpose: To determine the effects of light on seedlings germinated in the dark vs. the light. Materials: 20 popcorn kernels, 2 Ziploc bags, 2 damp paper towels, desk lamp. Procedure: Separate kernels into two different piles with equal number of kernels (10 kernels in each pile). Wet the paper towels until completely dampened. Place the dampened paper towels in the Ziploc bags, and then place 10 kernels on top of the paper towels in each bag. Make sure the kernels are on the paper towel in the bag and close the bag, but not completely (about 3/4 way closed). Wrap one of the Ziploc bags completely in aluminum foil. Leave the other one uncovered. Place both Ziploc bags under a desk lamp. After 7 days, check the bag that has been in the light as well as the bag that has been wrapped in aluminum foil. Compare the germinated kernels. You should definitely see a difference between the two. You should note mainly the color and stem length differences between the seedlings that germinated in light and those that germinated in darkness.
Think About This: 1. What did the kernels that germinated in the dark look like? (color of leaves, length of stems) 2. What did the kernels that germinated in the light look like? (color of leaves, length of stems) 3. Is light needed for germination and early growth? (Popcorn Board Education Exchange http://www.popcorn.org)
Here's a second resource for you: If your students have access to the internet, they can play plant detective with the University of Illinois. If not, you can download the teacher's guide and walk them through the experiment yourself. http://www.urbanext.uiuc.edu/gpe/
Best wishes with your classroom project!
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