Experiment: The Lighter Side of Plants

Materials:

• Small pot with soil
• Grass seeds

Step 1: Plant 20 to 30 grass seeds in a pot. Set the pot near, but not right next to, a window or other light source. Keep the soil moist but not soaking wet. The seeds will sprout in a few days. Do not turn or move the pot.

Step 2: As the grass begins to grow, observe that the plants bend toward the light source.

Step 3: After a few days, gently snip the tips (1–2 mm) off several blades of grass. Turn the pot 180° so that the plants are turned away from the light source.

Step 4: After several hours, observe the following:

• Did the grass move to face the light source?
• Did the plants that had the tips snipped off turn in the same way as those that did not have their tips snipped?

Step 5: After a few more days, repeat steps 3 & 4 but snip the tips of different plants. Observe the following:

• Which direction did the plants that were snipped in step 3 turn—more like the plants that were never snipped or the ones snipped in step 5?

Experiment: Touchy Plants

Materials:

• 4–5 sweet pea or morning glory seeds
• 1 small pot with soil
• 4 sticks, about 12" long and ¼" thick

Step 1: Plant the seeds in the soil. Place one end of each stick about 3 inches into the soil, evenly spaced along the edge of the pot. Place the pot in a sunny place and keep the soil moist but not soaked.

Step 2: After a few weeks, as the plants begin to grow, observe the tendrils as they come into contact with the sticks and the other plants. How do the tendrils that have touched something look different from the ones that have not?