Scientists Find Evidence Trees May Rest at Night too

'Fir trees early in the morning'

Laser-scans showed that trees droop their branches toward the end of the night, which may suggest they sleep.

BEACON TRANSCRIPTNo, they don’t snore, but they do lower their branches by as much as 10 centimeters during nighttime. Scientists believe that this aspect coupled with other physical changes may suggest that trees too ‘sleep’ at night.

Researchers have been studying birch trees in two countries and they noted that they lower their branches by up to 10 cm toward the end of the night.

András Zlinszky, one of the researchers involved in the study and senior scientist at the Hungary-based Center for Ecological Research, noted that the changes apply to whole trees. The team was startled by the scale of the changes within the day-night cycle.

The research team used laser beams on birch trees between sunset and sunrise to measure the time needed for the beams to bounce back. The resulting imagery showed that the branches of entire trees do move at night.

Eetu Puttonen, another scientist involved in the project and researcher at the Finnish Geospatial Research Institute in Finland, explained that similar experiments had been conducted only on small plants. But although they could have involved outdoor trees as well no one has ever done such tests.

Researchers laser-scanned two birch trees every 10 minutes over the course of a single night. They did not use photography to detect the changes because they would have needed a source of light which would have disturbed the trees’ ‘slumber.’

Researchers scanned the trees on calm nights to ensure that the winds do not influence the outcome. Norbert Pfeifer at the Technical University of Vienna in Austria noted that the changes observed in branches were definitely not triggered by other effects.

Zlinszky explained that trees lower their branches as the pressure of internal water, also known as the turgor pressure, tends to decline. Under this effect, branches and leaves become less rigid and tend to droop under their own weight.

Turgor pressure, on the other hand largely depends on photosynthesis which is no longer active in the absence of the sunlight, at night. During daytime, tree leaves are pointed higher to capture more sunlight and dodge the self-shading effect of nearby branches. But this phenomenon is useless at night when there is no sunlight to catch.

Scientists however do not know whether the drooping effect is caused by trees actually sleeping or by a drop in the pressure and absence of light.

“This remains to be decided,”

said Zlinszky.

Image Source: Wikimedia

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