Just watching sunflower saplings(?) move around through the day made me wonder.
For a plant to grow it’s needs sunlight and thus for you to understand better take a a bean and plant it on a dish cover it after it’s has started forming a bad and make a hole wherr the rays of sun will penetrate…you will notice theplant will grow toward tge hole….
Plant cells that are on the shadier side of the plant grow longer due to the plant hormone auxin. Direct sunlight (the sunny side) causes auxin to break down. This makes the plant bend toward the light. Udnder normal light conditons auxin is spread out evenly in the plant, causing it to go straight.
Chemical called auxin which promotes plant cell growth, sunshine destroys auxin so there is less on the side of the plant on which the sun shines so the opposite side grows more and bends towards the light. https://youtu.be/3q6C8coA5yc