You might never noticed it, but trees move even though there is no wind. Scientists have found that trees display minute and periodic pulses, as if they have subtle "heartbeats."
In the study, researchers from Denmark and Hungary investigated the overnight movement of 21 species of trees using terrestrial laser scanning, a high-precision three-dimensional surveying technique, the Guardian reported.
The researchers discovered the regular periodic changes in shape are synchronized across the whole plant and are shorter than a day-night cycle.
"We detected a previously unknown periodic movement of up to one centimeter in cycles of two to six hours," Andras Zlinszky at Aarhus University was quoted by the Guardian as saying.
But why does that happen? Researchers believed that the trees are pumping water. The movement has to be connected to variations in water pressure within the plants, Zlinszky said.
Other factors such as disease will also impact their motion, the researchers noted.
Trees lower their branches at night, entering a "sleep cycle," the study also found, echoing previous research results.