Acknowledgments
We acknowledge Zuping Yang, Guojun Zhou, Zhiyu Pu, Hongmei Zhou and Qiong Wu for help in the experimental process. This work was supported by the Top Science and Technology Talents Scheme of Yunnan Province [2009CI123], the Natural Science Foundation of Yunnan Province [2011FA034] and the CAS 135 program [XTBG-T02] to Z.-F. Xu. The authors gratefully acknowledge the Central Laboratory of the Xishuangbanna Tropical Botanical Garden for providing the research facilities.