The purpose of this project is to determine if roots and stems that grow out from germinating seeds are affected by an additional force perpendicular to the Earth's gravity.
Scientists are working on ways to grow food in space, as this will be very important if people are eventually to live on space stations for extended periods of time. One type of study that has been going on for years is hydroponics, which is growing plants with water, air, and nutrients, but no soil.
We have seen Hollywood science-fiction movies and TV shows depicting huge space stations that are rotating to make an artificial gravity inside. This is similar to the force that holds water in a pail when it is upside down as you swing it around with your arm or on a rope.
Normally, when a seed germinates, a stem grows skyward and a root extends down into the ground. Why? Is the root seeking water? Is gravity the factor that determines the direction of the sprouts? This may be important to know in the future as our quest for living in space becomes closer to reality.
Obviously, we will not be able to remove the effect of the Earth's gravity. Our experiment will determine if the spinning turntable exerts enough force in a different direction to act as an artificial gravity. Geotropism is the response of a plant to gravity.
Hypothesize that seeds planted while being spun on a record player turntable at 33 RPMs will germinate, and their roots and stems will grow parallel with the Earth, rather than perpendicular as they normally would.
- Record player turntable
- One package of radish seeds
- Five small plastic drinking cups (about 5 ounces)
- Sheet of stiff cardboard or poster board
- Paper glue
- Potting soil
- 15 days of time
LP (long-playing) record albums are 12 inches in diameter. Cut a 12-inch diameter circle from a piece of stiff cardboard or a sheet of poster board. With a pencil point or scissors, poke a hole in the exact center of the board, so it will slide down over a turntable's spindle.
Pour potting soil into five small plastic drinking cups, to a depth of one inch. Moisten the soil with water, but do not flood it.
Push one radish seed into the soil in each of four plastic cups. In the fifth cup, push three or four seeds. The fifth cup is our control cup, which will prove that the seeds in the pack and the growing environment are viable. Set this fifth cup aside in an out-of-the-way area in the room where your project will be placed.
Push the cardboard disc over the spindle and down onto the platter of a record player turntable. Be sure the disc moves when the turntable is spinning, and that the disc's hole is not too tight around the spindle.
At four opposite "sides" of the cardboard circle, place a few drops of glue (at 12, 3, 6, and 9 o'clock positions). Set a cup on each spot of glue. Let dry several hours.
Power up the turntable, setting it at a speed of 33 RPMs (revolutions per minute). Daily, add water equally to all five cups to keep the soil slightly moist. You may want to use an eyedropper to ensure an equal quantity of water is added to all cups. The turntable must run continually, except when you're adding water or making observations.
Make observations daily for 15 days, and write down your observations. Did the seeds germinate? If so, which direction (relative to the Earth's surface) did the roots grow? Which direction did the stems grow?
Write down the results of your experiment. Document all observations and data collected.
Come to a conclusion as to whether or not your hypothesis was correct.
- If the seeds germinated, did the stems grow toward the turntable's spindle and the roots away from it?
- Set the turntable to 45 RPMs and repeat the experiment. The higher turntable speed will exert more force on the seeds. Compare the results of seed germination at 33 RPMs and 45 RPMs.