What is phototropism?

Phototropism is the directional growth of a plant in response to a light stimulus.If it grows towards the light then it is positive (the most common type of phototropism) and if it grows away from the stimulus then it is negativeAll plants contain auxin which is a type of growth hormone which will accumulate in higher concentrations in the areas of the plant furthest from the light sourceEG: a plant is exposed to a left-handed-light-source so the right side of the plant has greater auxin concentration which acts as a type of growth hormone causing the cells on the right to elongate, the left-handed cells have the low auxin concentrations near the light source and don't elongate and remain constant. This causes the plant to begin to bend to the left and move positively towards the light source which allows greater light exposure for increased levels of photosynthesis