Question

Define the experiment to demonstrate postivephototropism and negative phototropism

Answer 1

The light from the lamp (1.) functions as a detectable change in the plant's environment. As a result, the plant exhibits a reaction of phototropism--directional growth (2.) toward the light stimulus.

Answer 2

Materials

3 small cups full of soil
Tape, a marker, and 3 sticky notes
Medium-sized box (such as a shoebox or a storage cube)
12 corn seeds
Aluminum foil
Small cookie sheet that fits inside the box (or another sheet of aluminum foil)
1 Straw
Water

Procedure

Plant four corn seeds in each of the soil cups. Make sure they’re evenly spaced, and plant them just a half inch under the dirt.Create labels for each of the following using a sticky note, and stick to one of each soil cup:ControlTipBaseWater the cups, and dump out any excess water (be careful not to tip the soil and seeds out). Place the cups on the cookie sheet or aluminum foil. This will prevent moisture and dirt from soaking through the box.Place the cups/cookie sheet setup inside of the box. Make sure it’s open on one side so that light is coming in from an angle. Place in a windowsill, with the open side facing the sun. (You might need to stack some books underneath it to support it, if your windowsill isn’t very wide.)Make four of each type of light-exclusion device:Shoot cap: Cut a small 2″ x 3″ square of aluminum foil. Wrap it around the tip of a straw to create a small, closed-ended metal cap, and slide it off. This will be placed over the tip of the growing shoot to cover any light coming in to the tip.Base sleeve: Cut a small 1/2″ x 3″ square of aluminum foil. Wrap it around the middle of a straw so it creates a small open-ended 1/2″ tall tube, and slide it off. This will be placed around the growing shoot so that it can grow through it.Check the cups each day. Once they send up a shoot about half an inch high, place either a shoot cap (on Tip seedlings) or a base sleeve (on Base seedlings) around them, depending on which cup they’re in. The control cup will get neither of the light exclusion devices. The seedlings might grow at different rates, so be sure to check each day to put the caps/sleeves on as needed. They grow fast once they germinate!Continue to water the seedlings as needed.