兰科新种巾唇兰的花粉团发育及分类学意义

巾唇兰属是我国新记录属，近十余年来先后在我国南方发现了两种，包括在云南发现的新种——巾唇兰（Pennilabium yunnanense）。利用解剖镜和石蜡切片技术观察了巾唇兰具有分类学意义的花形态特征和花粉团发育的胚胎学特征，结果如下。成熟花的合蕊柱短，无蕊柱足；花粉块由2个球形花粉团、粘盘和粘盘柄组成。在花药发育早期，花药原基分化出一对侧生并列药室；在小孢子母细胞时期，每个小孢子囊在两个药室相邻的内花药壁处分化出一段不贯穿药室的不育隔膜组织。在花药发育过程中，该隔膜组织逐渐被吸收降解，到花粉成熟时形成2个开口朝内的孔裂花粉团。发育成熟的花药壁共有4层，发育类型为单子叶型，绒毡层为单核、腺质型。在小孢子母细胞进入减数分裂阶段，表皮细胞变窄出现了降解，中层和绒毡层细胞也逐渐被吸收和降解；花药成熟时，花药壁仅剩下残缺的表皮和纤维状加厚明显的药室内壁。小孢子母细胞通过同时型胞质减数分裂形成小孢子四分体，其排列方式主要为正四面体形和左右对称，成熟花粉为2细胞型。本文从形态发育角度澄清了巾唇兰花粉团特征的描述，讨论了其花粉团发育特征的分类学意义，为兰科花药发育多样性提供了新资料。

Pollinia Development in a New Species of Pennilabium yunnanense(Orchidaceae)

Pennilabium J.J.Sm.is a newly recorded genus in China,including two species founded in Yunnan and Hainan.One of them is a new species of P.yunnanense.In this paper,floral morphology and pollina development in P.yunnanense were investigated.The column of a mature flower is short without column foot.Pollinarium unit is composed of two subglobose pollinia,stipe and viscidium.In the early stage,anther primordium is differentiated into a pair of lateral juxtaposed thecae.At the stage of microsporocyte,an incomplete sterile septum is formed adjacent to the inner anther wall between two thecae.During the microsporogenesis,the sterile septum becomes gradually degraded,resulting two pollinia with pore toward the inner anther wall disorganized.The hypodermal sporogenous cells produce 4-layered anther wall by periclinal divisions,including epidermis,endtothecium,middle layer,and a tapetum,which was of monocotyledonous type.Tapetum is uninuclear and secretory.Epidermis is not persistent,which becomes degraded as well as middle layer and tapetum.Fibrous thickenings occur on the entdothecium.Simultaneous cytokinesis results in tetrahedral and isobilateral microspore tetrads.Microspores undergo a mitosis leading to 2-celled pollen tetrads.Pollen tetrads arranged tightly and formed a subglobose pollinium in each theca.The embryological data on pollinia development of P.yunnanense could provide new insight for a better understanding of biodiversity and conservation in Orchidaceae.