1. State Key Laboratory of Systematic and Evolutionary Botany; Institute of Botany; Chinese Academy of Sciences; Beijing 100093 China
2. University of Chinese Academy of Sciences; Beijing 100049 China
3. State Key Laboratory of Plant Physiology and Biochemistry; College of Biological Science; China Agricultural University; Beijing 100193 China
4. Birbal Sahni Institute of Palaeobotany; 53 University Road Lucknow 226007 India
5. Beijing Radiation Center; Beijing 100875 China