So just like other living creatures, the trees in our woodlands and backyards "go to sleep" at night to rejuvenate themselves............"Plant movement is always closely connected with the water balance of individual cells, which is affected by the availability of light through photosynthesis".......... "Overnight, the leaves and branches of the trees seemed to droop gradually, reaching their lowest point a few hours before sunrise"............."When morning came, they returned to their original position within a few hours, although it is still uncertain if this "awakening" stems from the sunlight or their own internal clock"---András Zlinszky of the Hungarian Academy of Sciences.................I wonder if changing temperatures and up and down moisture levels will begin to interfere with trees, causing another stress factor for forests to battle(including exotic insects and disease)?.............Another limiting factor that will ripple up through the chain of life impacting our predator and prey suite of carnivores and herbivores?

sleep

Nature notes: even trees take 40 winks

•  Hana Carter 

26 MAY 2016 • 5:11PM

The branches of trees have been found to relax and
 recuperate at night, according to scientists at the 
Finnish Geospatial Research Institute

It was Charles Darwin who noted that flowers and most living organisms have day and night circadian rhythms, but only now have trees been studied in the same way.

Researchers used lasers to measure movement in two silver birch trees at night. They were monitored from dusk until morning on dry, windless nights in September. The time was close to the solar equinox, when daylight and night are about equal.

The scanners used infrared light to illuminate different parts of the tree, each for fractions of a second. The results showed that branches and leaves sagged at night, reaching their lowest position a few hours before sunrise. The leaves then perked up again in the early morning. 

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Trees Sleep Too: Infrared Laser Scanning Reveals Day-Night Cycle Of Trees

Scientists from Austria, Finland and Hungary used an infrared laser scanner to uncover the day-night cycle of trees and revealed that, like humans, they sleep at night.

By Tyler MacDonald | May 19, 2016 02:50 PM EDT

Scientists from Austria, Finland and Hungary used an 

infrared laser

 scanner to uncover the day-night cycle of trees and 

revealed that, like 

humans, they sleep at night. (Photo : Getty Images)

Almost all living organisms adapt their behavior to the circadian rhythm tied to day and night, and plants are no exception. However, to this day, studies have only focused on small plants grown in pots. Now, using laser scanning to examine the day-night cycle of trees, a team of scientists from Austria, Finland and Hungary has successfully examined the sleep movement of fully-grown trees and revealed that trees go to sleep, too.

"Our results show that the whole tree droops during night which can be seen as position change in leaves and branches," said Eetu Puttonen of the Finnish Geospatial Research Institute and lead author of the study. "The changes are not too large, only up to 10 cm for trees with a height of about five meters, but they were systematic and well within the accuracy of our instruments."

In order to ensure that the effects of weather and location didn't skew their results, the team conducted their experiment two times with two different trees; the first was examined in Finland and the second in Austria. Both tests were conducted under the same conditions: close to solar equinox and in a calm environment with no wind or condensation.

"Plant movement is always closely connected with the water balance of individual cells, which is affected by the availability of light through photosynthesis," said András Zlinszky of the Hungarian Academy of Sciencesand co-author of the study. "But changes in the shape of the plant are difficult to document even for small herbs as classical photography uses visible light that interferes with the sleep movement."Overnight, the leaves and branches of the trees seemed to droop gradually, reaching their lowest point a few hours before sunrise. When morning came, they returned to their original position within a few hours, although the team is still unsure if this "awakening" stems from the sunlight or their own internal clock.

Using a laser scanner, the team was able to overcome this difficulty through minimal plant disturbance due to its utilization of infrared light. This infrared light is reflected by the leaves, which allowed the team to map full-sized trees within minutes at a high resolution.

"The next step will be collecting tree point clouds repeatedly and comparing the results to water use measurements during day and night," Puttonen said. "This will give us a better understanding of the trees' daily tree water use and their influence on the local or regional climate."

The findings were published in the Feb. 29 issue of the journal Frontiers in Plant Science.