A young sunflower does more than turn toward the bright side of the sky.
During the day, young sunflower stems grow in a rhythm that carries their heads from east toward west. At night, that growth pattern reverses, bringing them east again before dawn. Researchers found that an internal circadian clock helps coordinate this daily movement with directional growth on opposite sides of the stem.
As the flower matures, it stops tracking and settles facing east. In the study, east-facing mature heads warmed earlier in the morning and received more pollinator visits than heads experimentally turned west. The plant’s changing posture is therefore tied both to its own daily timing and to the conditions its flowers meet when bees arrive.