1. Crop Physiology and Ecology Res. Div. National Inst. of Crop Science, Rural Development Administration 151 Seodundong Suwon 441‐857 Republic of Korea
2. Crop and Environ. Sciences Div. Int. Rice Res. Inst. (IRRI) DAPO Box 7777 Metro Manila the Philippines
3. Inst. of Biological Sciences, College of Arts and Sciences Univ. of the Philippines Los Baños, College Laguna 4031 the Philippines