There is often a belief that sunflower inflorescences exhibit heliotropism (they follow the sun).

An excerpt from the article 15 facts about sunflower

This is a half-truth, because only young inflorescences show this feature, mature ones remain motionless and are most often directed to the east. The young inflorescence begins its journey following the sun from the east, towards which it turns every night. Their movement is synchronized with the sun but does not depend on its rays, because the inflorescences follow the sun even on cloudy days and when they are moved under artificial light.