We all need our rest. And, according to new research, trees just might need sleep, too.
Scientists from Austria, Finland and Hungary used lasers to measure the overnight movements of birch trees—one in Finland and one in Austria. Their findings? The trees appeared to relax, with branches drooping at the tips by as many as 4 inches, reported Amy Ellis Nutt in a May 20 article in The Washington Post.
“It was a very clear effect and applied to the whole tree,” Andras Zlinsky of Hungary’s Centre for Ecological Research told New Scientist. “No one has observed this effect before at the scale of whole trees, and I was surprised by the extent of the changes.”
The study, published in Frontiers in Plant Science, noted that the movements happened systematically over several hours, ruling out the possible effects of wind and weather.
The team developed two hypotheses for why these trees droop. It could be due to a loss of turgor pressure, or internal water pressure, they said. Turgor pressure results from photosynthesis.
They also put forth the idea that the trees are following circadian rhythms, angling leaves and branches upward during the day to catch more sun and resting at night when such positioning is not necessary.
“The fact that some branches started returning to their daytime position already before sunrise,” the researchers wrote, suggests that Betula pendula is “governed by the internal circadian clock of the plant.”