Development of the male reproductive structures in Taxus yunnanensis

Taxus yunnanensis Cheng et L. K. Fu is a rare species endemic to Southeast Asia. The development of the male reproductive structures with emphasis on microsporogenesis and microgametogenesis are described for the first time. Our results showed that T. yunnanensis exhibits several features that are very different from other species of Taxus, such as pollination occurring in the same year as pollen cone initiation; production of several forms of tetrads including isobilateral, T-shaped or tetrahedron; shorter duration of microsporogenesis; longer duration of microgametogenesis; and production of more microsporophylls per pollen cone suggesting faster growth rate. Reports on the details of male reproductive development in Taxus spp. have focused on the activities of generative nuclei, while the activities of the sterile and tube nuclei are rarely mentioned. This paper provides a few more details about the sterile and tube nuclei, particularly, their relative position during the division of the generative nucleus to form two sperm. Furthermore, as our knowledge of the phenology of Taxus is confined to species that grow on high latitude areas, this paper provides information on the phenology of Taxus in low latitude areas. Overall, this paper provides several new insights about pollen cone development, microsporogenesis, and microgametogenesis in Taxus.