Trees were part of a recent and particular analysis made by researchers from Finland and Austria. The team presented evidence of how trees go through some physical changes at night, mostly how the branches drooped some centimeters like they were resting after a long day.
For the study, two silver birches from different geographical locations were analyzed by two separate experiments in Finland and Austria. 77 scans in Austria and 14 in Finland were performed to the trees through laser between sunset and sunrise, according to the study published in the journal Frontiers in Plant Science. Comparison through photography was not used due to the light could have had an effect in the plants.
Researchers studied the subjects, scientifically known as Petula Bendula, during similar outdoor conditions, although some differences about where the trees had grown were present, some of them were in plain fields while others in mountains. The team also avoided windy nights as they tried to conduct the scanning during normal conditions.
The results showed that the Finnish birch crown declined up to 5 centimeters compared to the situation at sunset. In the Austrian data, the lowest declination was 10 centimeters. Although there were significant differences among the data from the different locations, they both showed an important change during the night, the team said.
“It was a very clear effect, and applied to the whole tree,” András Zlinszky of the Centre for Ecological Research in Tihany, Hungary, said to the 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.”
Possible reasons
According to Zlinszky, the drooping effect could be due to the loss of internal water pressure within plant cells, a phenomenon referred as turgor pressure. It means branches and leaf stems are less rigid and more prone to drooping under their own weight, he added.
Turgor pressure is influenced as well by photosynthesis, in which the plants use sunlight to create sugar from carbon dioxide and water. This process stops in the dark, so it could explain why the branches drooped, Zlinsky added.
However, another reason could be linked to the resting of the branches. During the day, branches and leaves are angled higher, which allows them to catch more sunlight and to better perform the photosynthesis process. In the night, this energy-intensive does not have any point for the lack of sun.
The information needs further study and one thing that the results showed clearly was the potential of terrestrial laser scanning measurements in support of chronobiology, researchers concluded in the paper.
Source: Frontiers in Plant Science