Whether or not you believe that a tree will make a sound if it falls in a forest, the reason why it comes tumbling down in the first place could be because it fell asleep.

All jokes — and philosophical questions — aside, researches confirmed that trees sleep at night, or rather, have a day and night cycle that is similar to those observed in small plants.

Scientists conducted two separate experiments, one in Finland and one in Austria to make sure weather and location didn't play a role when attempting to find out if trees have some sort of resting period. Although conducted in different places geographically, both experiments were done at the same time of the year and in similar conditions.

The scientists used laser scanners on birch trees between sunset and sunrise to detect any changes in its shape. Eleven scans were taken of the birch tree in Finland and 77 of the one in Austria in total, with one taken every 10 minutes to create a time-lapse of the trees' movements.

Published in the journal Frontiers in Plant Science, the scientists found the branches drooped down as much as 10 centimeters at night. The trees' branches were at their lowest position a few hours before sunrise and returned to their upright position within a few hours of sunlight.

A decrease in the trees' internal water pressure, a phenomenon known as turgor pressure, could be the reason why the branches fall asleep. With less pressure, they begin to droop.

We all know from science class that trees undergo photosynthesis, the process where plants use energy from sunlight to make sugar (fuel), to live. Since there obviously is no sunlight at night, plants — and even trees — can be in the resting phase. The birch tree wouldn't have to have its branches and leaves reach up high during the night and can instead save energy by relaxing until the sun rises.

This makes sense, since flowers open up their pedals during the day to soak in light, and close up at night.

The rhythm of plants has been widely studied before, with Darwin first discovering in the late 1880s that plants do have a "sleep" cycle. However, this study is important because it is the first time researchers have observed that trees also sleep at night.

With the findings, the scientists can now study other trees to see if they behave similarly. This study makes us think twice about staying up all night making noise when camping so that we don't wake the trees.

Source: Frontiers in Plant Science

Photo: Steve Lyon | Flickr