1. Institut für Biologie, Pflanzenphysiologie, Freie Universität Berlin, Berlin, Germany
2. National Institute of Basic Biology, Nishigonaka 38, Myodaiji, Okazaki, Aichi 444‐8585, Japan
3. Department of Biology, Tokyo Metropolitan University, Minami‐Ohsawa, 1‐1, Hachioji‐shi, Tokyo 192‐0397, Japan