1. Tropism
Investigate the growth of plants in response to light (phototropism).
HL: Investigate the growth of plants in response to gravity (geotropism).

2. Investigate Tropism
Tropisms are the growth responses of a plant to a stimulus.
There are two tropisms on our course:
Geotropism is the growth response of a plant to gravity.
Phototropism is the growth response of a plant to light.
Plants can also respond to water, chemicals, temperature, electricity, and touch.

3. Investigate Phototropism
Place some germinating seeds onto a petri dish of moist cotton wool.
Place the petri dish into a covered shoe box which has a hole in one end
Leave it beside a window for a week.
Note the direction of plant growth.

4. Investigate Geotropism
Soak some broad beans in water for a day or two to begin germination.
Insert the seeds just inside the glass of a beaker of soil.
Place the seeds in a number of different orientations.
After a few days, check the direction of the growth of the seeds.