Why do sunflowers always face the sun? (Sunflowers in the sun)

1. Why do sunflowers always face the sun?

Sunflowers always face the sun mainly because they are affected by the light. Once it encounters light, it will rotate with the sun. However, generally speaking, its leaves and flowerpots will only move with the sun during the period from germination to flowering. After the flower disk blooms, it will face eastward.

The rhizome of sunflower contains a kind of "plant hormone" which avoids light and stimulates cell growth. When this growth hormone encounters sunlight, it will run to the side that is not facing the light to hide, causing the side facing the light to grow faster and the sunny side to grow slower, resulting in the phenomenon of growing towards the sun. Specifically, because most of its auxin is distributed on the backlit side, while the auxin concentration on the sunny side is lower, the backlit side grows faster, while the sunny side grows slower. This causes the stem to bend toward the light, making it grow toward the sun all the time.

2. How do sunflowers turn their heads at night?

The leaves and disk of the sunflower follow the sun from east to west during the day, but not in real time. Botanists have measured that the direction of its disk lags behind the sun by about 12 degrees, or 48 minutes. After the sun sets, the auxin redistributes, causing the sunflower to slowly turn back to its starting position and face east again. Around 3 a.m., it will face east and wait for the sun to rise.