College of Agronomy Hebei Agricultural University/Key Laboratory of Crop Growth Regulation of Hebei Province Baoding 071001 P.R.China;
Teaching Support and Service Center Hebei Radio and TV University Shijiazhuang 050080 P.R.China;
College of Plant Protection Hebei Agricultural University Baoding 071001 P.R.China;
Institute of Crop Sciences Chinese Academy of Agricultural Sciences/Key Laboratory of Crop Physiology and Production Ministry of Agriculture and Rural Affairs Beijing 100081 P.R.China;