2.81 Phototropism

Key Points:

1. Phototropism is the growth in response to light
2. Positive phototropism is the growth of the plant towards the light. With uniform light coming from all directions, the stem will grow upwards
3. However, with the same stem, and light coming from a lateral light source, the stem begins to grow towards the light source
4. In the example in which the stem grows towards the lateral light source, that is called positive phototropism
5. The understanding of this is that a compound called Auxin, which is a plant hormone and it causes more growth on one side, causing the bending of the stem and making the entire stem positively phototropic