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Branches and branches of large trees even "fall" up to four inches throughout the night

The next time you decide to travel to "the middle of the bush" to camp, it's important that you don't make too much noise, as the trees will be sleeping.

You didn't read it wrong. That's the fascinating conclusion of a team of scientists from Austria, Finland and Hungary who wanted to know whether large trees followed day/night cycles similar to those observed in small plants. Using laser scanners aimed at two white birch trees, the scientists recorded the physical changes indicative of nocturnal drowsiness, with the ends of the birch branches showing a small drop of up to four centimeters from the final period in the night.

"Our results show that every tree 'falls' overnight, which can be seen with a change in the position of leaves and branches," said Eetu Puttonen of Finnish Geospatial Research Institute. "The changes are not that big, only about ten centimeters for trees with a height of five meters, but they are systematic and matched the accuracy of our instruments."

In a publication in May 2016 on the Frontiers in Plant Science, the scientists explained how they scanned the two trees, one in Finland and one in Austria. The two trees were monitored independently, on quiet nights, and at the time of the solar equinox to ensure a good night duration. Although the tree branches were at their lowest position just before dawn, they returned to their original position within a few hours of the new day.

Researchers believe the drop effect is caused by a decrease in the internal water pressure within the tree, a phenomenon known as Turgor pressure. Without photosynthesis at night to guide the conversion of sunlight into sugar, trees conserve their energy by relaxing the branches and branches that would, during the day, be pointed towards the sun.

"It's a very clear effect, and it was applied all over the tree," said András Zlinszky of Center for Ecological Research, in Tihany, Hungary. "No one has ever noticed this effect before taking into account all parts of the trees, and I'm surprised by the extent of the changes."

The team will point their lasers at other forest species to see if they also have a circadian cycle. "I'm confident the finding applies to other trees as well," said Zlinszky.