How Does Gravity Affect Seedlings? - An Easy Kids Science Experiment

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Kids love easy science experiments that use seeds and plants. They love to watch things grow, and they love to experiment with the conditions needed to make the plants thrive. Early summer is the perfect time to start projects like this because the seedlings can be planted outside in the ground or in pots and (as long as you don't have any deer - deer love bean sprouts!) hopefully, your kids will get some beans by the fall.

Materials

• A clear glass jar - no lid necessary
• 2-3 paper towels
• Water
• A handful of bean seeds - we used bush green beans because it's what we had.
• Pencil

Instructions

1. The day before the experiment, soak 1 seed per child in water overnight. This will soften the seed coat and make it easier to dissect the seed.
2. Talk to your kids about seeds. Show them how every seed has a little white (usually white) spot on it called the hilum. This is where the seed was attached to the plant. The parts of the seed that will become the stem, first leaves, and the roots (called the embryo) are attached to the hilum. All the rest of the seed is food for the developing seedling, and all that is all covered by a seed coat that protects the embryo.
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   Photo source: http://www.myteamexplore.com/homework-help/science/seeds-and-germination.html

3. Help your kids to cut open the seed and try to find the embryo, food, and seed coat.
4. Next, get ready to "plant" your seeds. Tear off 2-3 clean paper towels. Fold in half then roll them up and stuff inside your jar to make a paper towel wall inside the jar. See below for how we did it.
5. Run some water in the jar, taking care to soak the paper towel and leave about ½" of water in the bottom.
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6. Our goal today is to find out how gravity affects the seeds, so you are going to orient your seeds in the jar in all different ways. Take a look at the hilum, and aim to have some seeds with the hilum up, some down, some out towards the jar, some in towards the paper towels, and some seeds standing up and down. You may have to poke the seeds with a pencil to get them angled the way you want. It's tricky to get them all the way you want without getting dropped down into the water, so this may require some adult help.
7. Put the jar in a warm, dark spot. Bean seeds germinate (break out of the seed) underground where there is no light.
8. Now you wait. Check your seeds every day, but be aware that green beans can take a few days to germinate. Make sure to keep a little water in the bottom so that the seeds have plenty of moisture.
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The Science

Seeds use gravity to put out roots and stems. The roots always grow down towards gravity, and stems always grow up away from gravity. No matter how you rotate the seed, the stem will always go up. Sometimes, it will initially come out going down, but it will curve around under the seed and come up on the other side. You can see this with the first root in the above 3 days picture. It grew up initially, but then curved around to grow down.

Cucumbers, watermelon, and squash only take about 4 days to germinate, so you could substitute those for quicker results. They have nice big seeds, so you'll still be able to tell how the seed is placed in the jar.

Extend the Experiment

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Super Science Summer

This is the first experiment of my Super Science Summer free at-home science camp for kids. Check out the main Super Science Summer page for all the details.