1. Department of Crop Science and Technology, College of Agriculture, South China Agricultural University, Guangzhou 510642, P. R. China
2. Scientific Observing and Experimental Station of Crop Cultivation in South China, Ministry of Agriculture, Guangzhou 510642, P. R. China
3. Yingdong College of Biology and Agriculture, Shaoguan University, Shaoguan 512005, P. R. China
4. Department of Anatomy and Cell Biology, University of Western Ontario, 1151 Richmond St., London, ON N6A5B8, Canada
5. Department of Botany, Division of Science and Technology, University of Education, Lahore 54770, Pakistan