It depends on
how you define "sleep," it has been proven that trees do relax their
branches at night, which might be a sign of snoozing, scientists said. To
discover this researchers set up lasers that measured the movements of two
silver birch trees (Betula pendula) at night. One tree was in Finland and the
other in Austria, and both were monitored from dusk until morning on dry,
windless nights in September for movements created by the environments to be
the minimum possible. This was close to the solar equinox, when daylight and
night time are about equal.The laser scanners used infrared light to illuminate
different parts of the tree, each for fractions of a second. This provided enough
detail to map each tree within minutes, the researchers said.
The silver
birches' branches and leaves sagged at night; they reached their lowest
position a few hours before sunrise, and then perked up again during the wee
hours of the morning, the researchers found.
So if this is
considered a form of sleep, trees after all might
sleep after dark, according to precise laser measurements that detected the
plants' branches drooping at night.
Eetu Puttonen
said: "Our results show that the whole tree droops during night, which can
be seen as position change in leaves and branches,", "The changes are
not too large, only up to 10 centimeters [4 inches] for trees with a height of
about 5 meters [16 feet]."
It's unclear if
the sun "woke up" the trees or if they relied on their own internal
circadian rhythm, the researchers said. But "the fact that some branches
started returning to their daytime position already before sunrise would
suggest this.The finding isn't too surprising, but oddly enough it hadn't been
studied until now, the researchers said. Most living organisms have day and
night circadian rhythms, and any gardener will notice that some plants open
their flowers in the morning and that some trees close their leaves at night.
Supplied by Carol Mar. 3º Y
