1. Laboratory of Crop Science, Graduate School of Agricultural and Life Sciences, University of Tokyo , 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657 Japan
2. Laboratory of Plant Physiology, Department of Biological Production, Akita Prefectural University , 241-438 Kaidobata-Nishi, Shimoshinjo-nakano, Akita, 010-0195 Japan
3. Laboratory of Stress Cytology, Graduate School of Agricultural Science, Kobe University , 1-1 Rokkoudai-chou, Nada-ku, Kobe, Hyogo, 657-8501 Japan
4. Laboratory of Tropical Crop Science, Graduate School of Agricultural Science, Kobe University , 1-1 Rokkoudai-chou, Nada-ku, Kobe, Hyogo, 657-8501 Japan