Mystery Unlocked: Here's How 'Animal-Like' Sunflowers Dance in the Sun

Researchers from UC Davis and UC Berkeley have solved the mystery of how sunflowers dance in the sun throughout the day. The researchers said that plant hormones, internal clock and the sun itself are the factors causing these yellow flowers to move.

According to the study published in the journal Science, just like animals, sunflowers have internal clocks that can affect and regulate growth.

Scientists have long been aware that plants have internal clock genes just like those of animals. However, senior author Stacey Harmer from UC Davis wanted to know the link of these clock genes with a hormone called auxin that control stem growth.

To do this, Harmer and her team tried to stake the flowers so that they would not move. The constrained, frail flowers were then moved to an indoor growth chamber, where the sunflowers swang back and forth even without a direct response to the sun. The observations revealed that the sunflowers are not solely controlled by the sun but have internal rhythms too.

The study reveals that this circadian regulation results to a light-responsive growth, where the eastern side of the sunflower's stem elongate more during the day while its western side grow more actively during night.

This movement results to a 180-degree rotation of the sunflower in order to capture sunlight. After a sunflower is fully grown, the plant's internal clock stops. The plant is then permanently positioned to face the east to harness sunlight during the morning and facilitate pollination, Berkeley News reports.

“Before our experiments, few studies -- the latest more than 50 years ago -- had assessed how sunflowers returned at night, and they had suggested some internal ‘habit’ was involved but did not directly implicate the clock,” said Benjamin Blackman, an assistant professor of plant and microbial biology at UC Berkeley and co-author of the study.

Harmer explains via Seeker that plants are very sensitive to their environment and possess senses that are alike with what humans have. However, the difference lies on the "time scale of many of the responses."

"Plants actually have color vision. They have several families of photoreceptors that allow them to see many different wavelengths of light: UV, blue, green, red, far-red," Harmer continued. "Note that plants can see wavelengths of light that humans can't detect (UV and far-red). They use these photoreceptors, in particular, those that are sensitive to blue light, to track the sun."

The study has shown that sunflower growth is affected by light as well as an internal circadian rhythm. The internal clock's behavior and adaptive functions to control plant growth could open doors to future applications in other species, Blackman noted.