Science Of Sleep: Even Trees Rest At Night

Plants and trees have always been mysterious to scientists - while their physical workings have been studied over and over again, the questions still burn: do trees feel, do they communicate with others, or do they also need to rest like other living creatures?

Nobody really knows the answers to these questions, but while there may be the possibility that fruit-bearing plants can grow better if they listen to classical music, these studies have not been proven.

What scientists did find out, however, is that trees do take their own rests. According to New Scientist, branches of birch trees were found to droop by as much as 10 centimeters at the tips near the end of the night.

Andras Zlinszky of the Centre for Ecological research in Tihany, Hungary, said, "It was a very clear effect, and applied to the whole tree. No one has observed this effect before at the scale of whole trees, and I was surprised by the extent of the changes."

Their study published in Frontiers in Plant Science is the first of its kind. They scanned birch trees - one in Finland, and one in Austria - over the course of a single night. They made laser scans of the birch trees - eleven of the Finnish tree, or one per hour, and 77 of the Austrian Tree, or one every 10 minutes. With the use of their laser scanners, they will not have to disturb the trees with light, and were able to get a clearer outcome.

Scanning was also done in calm nights to avoid wind effects, and during the solar equinox to ensure the same length of night. The drooping effect may be caused by loss of internal water pressure in the plant cells, called the turgor pressure, and it is shown by the way stems are less rigid and they are more prone to drooping under their own weight.

So why do they think that trees are "resting" their branches? During the day, the branches and leaves are angled higher to help them catch more sunlight, but this is energy intensive and is pointless at night, when light is scarce.

But is the drooping deliberate as a form of rest? Zlinszky said that there is no surety, and that still remains to be decided.