What is the phototropism?
The Phototropism is the movement of plant structures in response to light. The Phototropism may be negative or positive. The Positive phototropism is that in which the plant movement (or growth) is towards the light source and the negative phototropism is that in which the movement (or growth) is inverse, away from the light source.
The Phototropism relates to the auxins ever since the exposition of one side of the plant to light makes these hormones concentrate in the darker side. This fact makes auxin action upon the stem to be positive that is the growth of the darker side is more intense and the plant arcs towards the lighter side and In the root (when submitted to light, in general experimentally) the auxin action is negative (over the positive range), the growth of the darker side is inhibited and the root curves towards this side.