Researchers from Australia, Finland and Hungary use lasers to measure movements of birch trees. They found some rare things during the hours of darkness where the trees appeared relaxed or droop their branches at tips by 4 inches.

“It was a very clear effect and applied to the whole tree. No one has observed this effect before at the scale of whole trees, and I was surprised by the extent of the changes,” Andras Zelinsky of Hungary’s Centre for Ecological Research told New Scientist this week.

At the center, there were two birches where one is in Finland and other is in Austria. Lasers are used to scan their canopies from sunset to sunrise at regular intervals. All this happens in a course of overnight. the conditions were same almost everywhere no rain, little wind and the length of darkness are comparatively equal during the solar equinox.

“The results obtained from the measurements showed that the crown movement in the Finnish and the branch movement in the Austrian study case presented similar temporal response. Close to sunrise, the branches were hanging lower than at the time of sunset. The movements were observed to happen systematically over a time span of several hours, which ruled out occasional wind effects,” the scientists concluded in their study.

The two hypotheses were found like drooping could be because of loss of internal pressure of water, which is called turgor pressure causing the branches and leaf stem loses their rigidity. The use of sunlight to create sugar from carbon dioxide and water that which happens during a day. With this darkness, the trees would relax.