Phototropism refers to the movement of of plant body or parts towards or away from the light. There are two types of phototropism i. e. positive phototropism and negative phototropism.
In positive phototropism, the parts of plant body moves toward light. Movements of radical in the upward direction after seed emergence is the example of positive phototropism.
In negative phototropism, the body part of plant moves away from the light. Roots are the example of negative phototropism.
Stem tips usually move towards the source of light. That's an example of a positive response. While the roots usually move away from it: which is a negative response.
Cells expand less on the lit side and expand more on the shady side of the plant.
