How do sunflowers turn back at night? Why do they always face the sun?

First, how to wait until the sun goes down at night, there is no sunshine. It will slowly swing back, not the "sharp turn" in the rumor. When there is no light, the auxin in its body will be rearranged and distributed more evenly, so that it can slowly turn back to its original position. At about 3 am, it has turned back to its original position and will face the east again, waiting for the sun to rise and rotate with the sun to usher in a new day.

Second, why does it always face the sun from the moment when its bud just grows to the moment when it blooms? In order to absorb sunlight and get nutrients, it always faces the sun The auxin on its back will rise, stimulating the cells on the side facing away from the light to slowly elongate, thus rotating with the sunlight. But when the disk is in full bloom, it will not rotate with the sun, but will be fixed in the east to obtain nutrients.