Geotropism: Plant's Response and Movement Due to Gravity (page 2)

Design Your Own Experiment

1. Demonstrate the effect of gravity on mature plants by laying one small houseplant on its side (see A in Figure 12.3). Place a covering or netting over the soil of a second small houseplant to keep it in the pot, and then hang the plant upside down (see B in Figure 12.3). Place both plants inside a dark closet or under a cardboard box to prevent them from responding to light. Observe the position of the stems of each plant after one week. Carefully remove the soil from around the roots of each plant and observe their direction in relationship to the direction of growth of the stems.
2. Does the direction that a seed is planted affect the growth of the stems and roots? Fold a paper towel and line the inside of a drinking glass with it. Stuff pieces of paper towels into the glass to hold the paper lining in place. Place a strip of masking tape around the outside of the glass and mark the tape with arrows pointing up, down, left, and right. Place one pinto bean (between the glass and the paper towel) under each arrow. Make sure the bean's hilum (scar on the inside curved side) is pointing in the direction indicated by the arrow (see Figure 12.4). Moisten the paper towel and keep it moist, but not dripping wet. Place the glass inside a dark closet. Observe the direction of the stems and roots daily for seven days.

Get the Facts

1. How does a plant respond to a low-gravity field as in a spacecraft? Write to NASA (L.B.J. Center, 2101 NASA Rd #1, AP-4, Houston, TX 77058) and request information about growing plants in space.
2. How does a simulated-gravity field such as that produced by a rotating space station affect the direction of stem and root growth? A rotating turntable on a record player can produce a simulated field of gravity. More information on growing seeds in this simulated-gravity field can be found in the experiment titled "In or Out?" (p. 50) in Janice VanCleave's Biology for Every Kid (New York: Wiley, 1990).

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