Can you imagine trees taking a nap in the afternoon or succumbing into deep slumber at night? For the first time ever, scientists have obtained direct observations about the physical changes that occur in trees, that are similar to the act of sleeping in animals and even humans, revealing a day and night rhythm.

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In this new study, an international team of researchers utilized laser scanners to study two trees and examined a cloud composed of millions of different points that are laid out on their surface areas. Using this new data, researchers were able to learn that trees apparently show movement during the night, a natural phenomena that scientists have been observing in smaller plants.

According to Eetu Puttonen of the Finnish Geospatial Research Institute, these results show how the entire tree stoops down during night time that can be observed as a position change among leaves and branches. Although these changes are subtle enough, the team measured 10 centimeters for trees with an average of height of five meters, which reveals a systematic process that have been accurately detected by instruments.

In order to distinguish and determine these crucial effects from weather and location, researchers studied one tree in Finland and another tree in Austria, where weather conditions are milder and there is no wind. During observations, the leaves and branches drooped significantly in a gradual manner, where the maximum position was achieved after around two hours before sunrise. During the morning, the trees returned to their original state of rigidity, in a matter of a few hours.   

According to András Zlinszky from Hungary's Centre for Ecological Research, this drooping effect is most likely caused when the tree loses its internal water pressure inside the tree's cells, which is a natural event known as turgor pressure. Zlinsky says that this entails less rigid branches and leaf stems that become more prone to drooping on their own weight. Since turgor pressure is controlled by photosynthesis, this drooping happens when the sun goes down and into the night as photosynthesis stops. 

This new study is published in the journal, Frontiers in Plant Science.

Tagstrees, Photosynthesis, trees sleep at night, sleeping trees