Secret of plant geometry revealed

While the other principle features governing the architecture of plants such as the control of the number of branches and positioning around the main shoot are now well understood, scientists have long puzzled over how plants set and maintain the angle of their lateral branches relative to gravity. The mechanism is fundamental to understanding the shape of the plants around us: explaining how, for instance, a young Lombardy poplar sends its branches up close to the vertical while an oak sapling’s spread is much flatter. Dr Stefan Kepinski, senior lecturer in the University of Leeds’ Faculty of Biological Sciences and lead author of a paper in the journal Current Biology that gets to the bottom of the mystery, said: “We began working on this after a train commute into Leeds. Looking out of the window, I was struck by the fact that the way we recognise tree and other plant species from a distance is largely informed by the angle at which their branches grow. “These characteristic angles are all around us and the same thing is happening underground; different varieties within species often have very distinct root-system architectures that are determined mainly by the growth angle of lateral roots,” Kepinski said. The apparently simple puzzle of how a plant sets and maintains these angles in its architecture is complicated by the fact that the angle of root and shoot branches is not usually set relative to the main root or stem from which they grow but relative to gravity.