How roots find their way to water

For his experiment, Daniel von Wangenheim, a former doctoral researcher in Professor Ernst Stelzer's Laboratory for Physical Biology and most lately a postdoc at Malcolm Ben-nett's, mounted thale cress roots along their length in a nutrient solution. They were, how-ever, not completely immersed and their upper side left exposed to the air. He then ob-served with the help of a high-resolution 3D microscope how the roots branched out.

To his surprise, he discovered that almost as many lateral roots formed on the air side as on the side in contact with the nutrient solution. As he continued to follow the growth of the roots with each cell division in the microscope, it became evident that the new cells drive the tip of the root in the direction of water from the very outset, meaning that if a lateral root had formed on the air side, it grew in the direction of the agar plate.

"It's therefore clear that plants first of all spread their roots in all directions, but the root obvi-ously knows from the very first cell divisions on where it can find water and nutrients," says Daniel von Wangenheim, summarizing the results. "In this way, plants can react flexibly to an environment with fluctuating resources."