Orienting Growth in Response to Gravity

On Earth, the roots of a plant always grow downwards and the stem and leave grows upwards. This is due to gravity. In space, plants do not know which way is "down", because plants do not receive any clues from gravity. Orbiting spacecraft are always in a state of freefall which gets rid of the effects of gravity so plant parts grow in all directions. In some space experiments, roots and stems have been seen to grow in the same direction.

Long-term plant growth in space may require artificial gravity to be created onboard the spacecraft. This can be done by changes in speed or direction that produces forces - like the effects of gravity - to be exerted on the plants. Continuous rotation of a plant growth chamber can produce long-term gravity-like effects.

Purpose

• To demonstrate geotropism in plants

Materials and Equipment

• Several sheets of paper towel
• Garden seeds (beans, peas, radishes, navy beans work very well and are inexpensive!)
• Plastic bags with seal
• Water
• Thumb tacks

Method

1. Fold the paper towel so that it will fit inside the plastic bag. Soak it thoroughly with water.
2. Place several seeds on top of the paper towel and carefully put the paper towel inside the bag. Close the bag partially to allow some air to get in. Label the plastic bag.
3. Attach the bag to a bulletin board being careful that the seeds stay in place between the paper towel and the plastic bag.
4. Repeat with different types of seeds.
5. Observe the growth of the seed over several days and record the findings.
6. Once the roots have sprouted, turn the bag 180 degrees and attach to the bulletin board. Observe for several more days.
7. Continue to turn the bag at different angles and record the pattern of root and stem growth.

Observations/Results

• Record your observations.
• Make sketches of the plants at different stages of growth and label diagrams.
• Post your results in your Team Blog.

Questions

• Why did the roots continue to grow downwards after the bag was turned over?
• How will scientists create an area for growing plants on the space station?
• What type of food will astronauts have to eat on long-duration flights?