Answer:
Phototropism is the measure of growth when the sun is facing the plant to help it grow or survive. Photo means sunlight. There are chlorophylls in the leaves of the plants, which are small, microscopic sized green organisms. These chlorphylls collect the sunlight from the sun and transfers the light to glucose. Glucose is a thick sugary substance that the plant needs to feed on to survive. There are also other plants that don't have to depend on sunlight to survive, such as red algae. Red algae actually depends on eating smaller organisms when dwelling too deep in the sea to capture sunlight, but when near surface, it has the ability to transfer the sunlight to glucose. So red algae are both photosynthetic and autotrophic. Photosythetic means that a plant has the ability to absorb sunlight and transfer it to glucose. Autotrophic means that a plant has the ability to devour smaller organisms to survive. I hope this answers your question! :)