Plants need light to live and to grow – this has been known since time immemorial. And if you look carefully in the summertime, you can see how young sunflowers turn their heads from East to West each day, following the path of the sun, so that they get the maximum possible light at any time of day. However, the processes that take place within plants when the sun’s rays fall on them have never been thoroughly researched. Freiburg plant physiologist Prof. Dr. Andreas Hiltbrunner at the Institute of Biology II is a member of the Cluster of Excellence CIBSS – Centre for Integrative Biological Signalling Studies and studies the signals that plants send out in daylight. In his experiments he compares the different signal paths and light-sensitive receptors of moss and the thale cress, Arabidopsis thaliana. He is mainly interested in the red part of the light spectrum, because different red waves trigger different mechanisms in plants.