2.81 Positive Phototropism.

• Positive phototropism - positive suggests that it is towards light.
•                                    - photo refers to light.
•                                    - tropism refers to growth in response to this light.

•    uniform light coming from all directions means the stem will grow forwards and upwards.

•     however, if the same stem only has light coming from one side (lateral light source) it causes the plant to bend in a grove towards the light.

•  the light on this side causes the opposite side of the stems auxin (plant growth hormone) to grow more which causes the bending.