2.81 Phototropism

Positive Phototropism:
- Photo = light, Tropism = growth in response to light
- Positive = growth towards the light
- Stem: (example of positive phototropism growth)
- It will grow forwards and upwards when there is light coming from all directions
- The plant bends in the growth towards the lateral light source because the light causes the movement to the opposite side of a compound: Auxin (plant hormone) which causes more growth on the opposite side than the side which has light, therefore, the plant bends.

2.79 Plants and Stimuli

- Stimuli are changes in the environment (e.g. temperature, light)
- Plants have receptors which detect stimuli and turns into a response
- Responses take the form of growth - this type of response (growth in response to stimulus) is called a Tropism
- Tropisms involving light = Phototropism
- Tropism involving response to gravity = Geotropism
- Connection between receptor and response takes form of plant hormones called Plant Growth Regulators (e.g. Auxin)