Jan. 30 (UPI) -- As trees get taller and heavier, sprouting branches in various directions, they must augment their support structure -- their trunk -- to maintain stability. Until now, scientists weren't sure exactly how they did it.
New research suggests most healthy trees have a built in system, called vertical proprioception, that allows them to respond to weight increases with radial growth of the stem.
Scientists were able to demonstrate the vertical proprioception system by altering the aerial weight of a downy birch trees and measuring the response. Researchers found most trees responded to added weight by thickening their trunk.
The response was most pronounced in trees with an ability to bend and flex their trunks. Static trees weren't able to thicken their trunk as efficiently in response to added aerial weight.
"Even though the idea of plants sensing their own weight and thickening their stem accordingly sounds intuitive, our study is the first one to address this question in trees," Juan Alonso-Serra, professor of biological and environmental Sciences at the University of Helsinki, said in a news release.
To further illuminate the vertical proprioception system, researchers compared the trunk-thickening abilities of normal downy birch trees to a naturally occurring species of birch mutant called elimäki. After growing upright for three months, elimäki trees suddenly bend from the base and collapses.
When scientists added weight to the branches of elimäki trees during their initial three months of normal growth, they were unable to increase their trunk thickness in response. Scientists tracked this inability to a single position within the birch genome. In the future, researchers hope to isolate the specific mutated gene responsible for the elimäki's abnormal growth pattern.
Researchers published their analysis of the birch tree and its vertical proprioception abilities this week in the journal Current Biology.