1. C. Bock, M. Hauck (corresponding author), Albrecht von Haller Institute of Plant Sciences, University of Göttingen, Untere Karspüle 2, D-37073 Göttingen, Germany; e-mail: mhauck@gwdg.de
2. E. Fischer, Institute of Integrated Natural Sciences, Dept. Biology, University of Koblenz-Landau, Universitätsstraße 1, D-56070 Koblenz, Germany.