A new study published this week in the journal Science shows that young sunflowers track the sun all day long with their faces making a full 180 degree rotation before returning to their starting points in anticipation of sunrise.
Time-lapse video captured the sunflowers’ strange movements
Following the viewing of time-lapse videos of this movement, circadian biologist Stacey Harmer, a professor at the University of California-Davis set out on a study in the hopes of understanding why and how they did this.
“At nighttime, you could see the whole plant rearranging itself, and it was such an amazing thing,” said professor Harmer. “I tell my students all the time that plants are capable of incredible things — we just don’t notice because their time scale is different than ours.”
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She and her team published their findings on Thursday.
In order to complete their study, the team planted a field of sunflowers with each in their own pot so that variables could be brought into the mix easier.
“They are really great plants, and we kept finding out fascinating things about them,” Harmer said. Contrary to popular belief, she points out that adults don’t follow the sun put always face east. However, before maturity the flowers follow the sun throughout the day before their reorienting each night.
Strange behavior when variables were brought into the study
“A really common misconception is that mature sunflowers follow the sun, actually, they do not,” Harmer told the Los Angeles Times. “Mature sunflowers always face east.”
Not only do sunflowers’ faces make a full 180 degree rotation but they can do it in as few as eight hours or do it in a “lazy” twelve hours depending on how much sunlight they are afforded.
In order to make this move, the researchers found that the the east side of the stem grew longer during the day in order to make the turn to the west, while at night the west side of the stem grew to make the return. What baffled the researchers a bit was the fact that when they moved the plants into a laboratory environment where they were given direct overhead lighting that was fixed in place and the young sunflowers still did their “dance.”
Based on this, the researchers realized that this movement was likely the result of some sort of internal clock rather than the movement of the sun. This was confirmed when they put the flowers on a 30-hour light cycle and the sunflowers went a bit wonky.
It became clear to the researchers that the sunflowers are benefited by this “dance” after one of the researchers rotated the pots to the west in the evening causing those plants to grow 10% less than the control group sunflowers.
“That’s a really big difference,” Harmer said.
“Just like people, plants rely on the daily rhythms of day and night to function,” Anne Sylvester, the director of the National Science Foundation’s Plant Genome Research Program, said in a press release. The organization funded the study of the flowers odd behavior. “Sunflowers, like solar panel arrays, follow the sun from east to west. These researchers tap into information in the sunflower genome to understand how and why sunflowers track the sun.”
Harmer admits they want to study the sunflowers more in the future pointing out that “it’s the first example of a plant’s clock modulating growth in a natural environment, and having real repercussions for the plant,” according to ScienceDaily.