Pollination Biology in Taxus yunnanensis

Taxus yunnanensis,its distribution extends from Burma through southwest China to Bhutan.The structure of mature ovules and microspores were examined using paraffin embedded samples,SEM and stain-clearing.The pollen drops’activities were observed in the field. The results show that:The mature microspores were uninucleate,non-saccate,with numerous orbicules,and live and dead microspores expanded rapidly after hydration in vitro.A single ovule is borne in axil of a leave.The microspores were shed from mid-November to mid-December,and base-bend ovules are found from late-November to mid-February.The existed duration of pollen drops was shorter in shedding period or with hand-pollination,and the pollen drop didn’t reoccur once pollinated.The existed duration of pollen drops was longer after shedding time,and the pollen drops could reoccur after disappeared.The pollination mechanisms in Taxus are considered as follows:(1)The pollen drops are big and naked,and its duration is long,these can improve the pollination efficiency.(2)Microspores can keep alive in room temperature a long time,and cann’t fly in long distance,this is beneficial to keep higher concentration.(3)Long duration of ovules’maturity can meet variable shedding period.Raining in pollination and low population density may be major factors that affect pollination efficiency.