How do plants alter the way in which they grow in response to light?

Plants have photoreceptors in the tips of their shoots. If light is detected from a specific direction, the plant will produce auxins which diffuse fown the shoot of the plant. The auxins increase in concentration on the shaded side of the plant. This causes these cells to elongate on the shaded side of the plant compared to the side of the plant in the light resulting in an overal directional growth towards the light. This is known as phototropism.