Biologists at the University of California have unlocked the mystery of the sunflower’s dance. It seems that the plants anticipate sunrise and turn toward east overnight because of their internal clocks.
This phenomenon is also called circadian rhythm which is a behavior tied to an internal clock that follows a roughly 24-hour cycle.
The young sunflower heads east at dawn to confront the sun and then gradually turns west as the sun travels the sky. At night it slowly turns back east to start its cycle once again.
The researchers conducting this experiment turned some plants away from the sun and tied them down so they couldn’t move. These plant’s biomass and leave area had decreased in contrast to flowers that could follow the sun.
Moreover, the plants exposed to artificial light could still track the movement and return at night when the artificial day was closed. However, the sunflower’s dance only occurred when the artificial day was close to a standard 24-circle and stopped when it was closer to 30 hours.
According to the press release, mature flowers have a different approach towards the sun. When their growth slows down, the circadian clock changes and assures that the sunflower has a stronger response to the morning sunlight than in the afternoon, so, during the day, it stops moving westward.
Similar to humans, plants also depend on their day and night rhythm to function. During the day, this internal clock sends information to the eastern sides of their stems, telling the cells to extend longer which makes the plant bend westward.
At night, because of the contrary message, the sunflowers incline back toward the east. It appears that the plants have two growth mechanisms. The first one, based on the available light sets a basic rate growth for the sunflower. The second, controlled by the circadian clock guided by the light’s direction influences the stem to grow more on one side than the other, and this is how the plant’s movement is made.
The researchers also compared the results from mature sunflowers they turned to face west to those facing east. It proved that the east-facing blooms attracted five times more helpful pollinators than the west-facing plants.