1. Sensitivity in Plants
Chapter 15

2. Tropisms A tropism is the response of a plant to a stimulus
There are different types of Tropisms
Phototropism
Geotropism
Hydrotropism

3. Phototropism Phototropism is the response of a plant to light.
The stem grows towards the light to allow more photosynthesis to take place.

4. To show phototropism in plants
1. Set up apparatus as shown in diagram
2. Leave in a bright warm place for a few days
Results
In A the cress seeds bend towards the light
In B the cress seeds grow straight upwards
In C the cress seeds will have poorly formed yellow leaves

5. Geotropism Geotropism is the response of a plant to gravity
This ensures that the roots grow down into the soil for anchorage, water and minerals.

6. Geotropism

7. To show Geotropism in Plants
1.Set up apparatus as shown in diagram
2.Turn the bean seeds in different directions.
Result
No matter which way the bean
seed is turned, the radicle(root)
will grow downwards and the
plumule(shoot) will grow upwards