How does phototropism occur in plants?

The growth and movement of a plant shoot towards the light is known as phototropism. Example-The movement of sunflower in the direction of sun is Phototropism. The phototropic movement is generally caused by the plant hormone called auxin. Concentration of auxin changes in a particular plant part, in response to the direction of light. The concentration of auxin increases on the dark side and decreases on the illuminated side. Due to the presence of more auxin, the part of the plant stem which is away from light grows faster, causing it to bend towards light.