Please give me the answer to the A-level Biology Question How is the process by which plants turn towards a light source called and what is the role of auxin (IAA) in it?

A-level Biology Help >>>>> What is the process through the plants' movements toward a source of light called and what's the role that auxin (IAA) in this process? The process is known as phototropism ('photo'-light"tropism" - the tendency of an animal plant to move or turn when a stimulus is presented').
IAA (Indole Acetic Acid) is a hormone found in plants that is part of a class known as auxins. It is created by mesenchymal cells and is involved during the phototropism process, by encouraging cell extension. When the plant is exposed the light source in a unilateral manner (in other words , illuminated only from one angle) The amount of auxin on the side with shade is increased. The auxin increases the proton pumping in the membranes of adjacent cells, causing these cells to move protons through their surroundings. The pH drop creates optimal conditions for expansins, proteins that work to open the cell walls which in turn encourages the cell's elongation. In the process the uneven development, the portion of the plant's tip is turned towards an energy source.
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