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
1. Place some germinating seeds onto a petri dish of moist
cotton wool.
2. Place the petri dish into a covered shoe box which has
a hole in one end
3. Leave it beside a window for a week.
4. Note the direction of plant growth.
4
Investigate Geotropism
1. Soak some broad beans in
water for a day or two to
begin germination.
2. Insert the seeds just inside the
glass of a beaker of soil.
3. Place the seeds in a number
of different orientations.
4. After a few days, check the
direction of the growth of the
seeds.