Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, Zürich, 8008, Switzerland. marcschmid@gmx.ch.|Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, Zürich, 8008, Switzerland. sgrob@botinst.uzh.ch.|Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, Zürich, 8008, Switzerland. grossnik@botinst.uzh.ch.