1. When the sun just rises, the sunflower will gradually rise with the change of the position of the sun until it is completely lifted.
When the sun goes down, the sunflower will gradually lower its head until it is completely low.
This characteristic of sunflower is mainly due to the sensitivity of its auxin to light. Auxin will change its distribution with the change of light, which will cause the sunflower's stem to bend, which will lead to the sunflower's head rising and bowing.
However, it should be noted that if there is no sun at night, the sunflower will also lower its head as the sun sets and wait for the sun to rise again the next day. In addition, although sunflower always faces the sun, it doesn't face the sun all day. For example, on a cloudy day, or when the sun is not strong, the sunflower may just raise its head slightly.
The above information is for reference only. If necessary, it is recommended to consult relevant literature or consult people who have planted sunflowers.