Study on the Reproductive Characteristics and Pollination Biology of Wiktroemia monnula

In order to explain the low seed setting rate of Wiktroemia monnula, the characteristics of flower, pollen viability, stigma accessibility, breeding system and pollination biology were investigated. The results showed that the Wiktroemia monnula was bisexual, with small flower opening and long calyx tube. The stigmas were buried deep inside the calyx tube, and the stamens were arranged in the middle and upper part of the calyx tube. The pollen and stigma morphology of Wiktroemia monnula were normal and there were no developmental defects. The dynamic observation of pollen activity and stigma receptivity of Wiktroemia monnula showed that 6-24 hours after flowering was the effective pollination stage（EPP）, with higher pollen activity and stronger stigma receptivity. Pollination biology observations showed that wind pollination contributed a lot to the reproduction of Wiktroemia monnula. Due to the long calyx tube, animal pollination was difficult, and only small insects such as louse and thrips were possible potential pollinators. Combined with the pollen ovular ratio（P/O）, hybridization index（OCI） and pollination biology observations, it was concluded that the breeding system of Wiktroemia monnula was mainly outcrossed, self-compatible, and sometimes needed pollinators. These results indicated that the tubular flower structure of Wiktroemia monnula made cross-pollination difficult, which could be the main reason for the low natural seed setting rate of Wiktroemia monnula.