传统傣药竹叶兰的花粉团发育及分类学意义

Pollinia development in Arundina graminifolia (Orchidaceae) with taxonomic implications

该研究利用石蜡切片技术观察并描述了兰科单型属竹叶兰属的花粉团发育过程,包括花形态解剖特征、8个花粉团的形成机制、花药壁发育模式、小孢子发生及雄配子体发育等特征,为该属复杂的系统亲缘关系提供胚胎学证据。结果表明:(1)成熟花药有两个药室,每个药室有4个一簇金色的花粉团,被白色花药帽;早期花药原基分化出的一对并列侧生药室,每个药室中央的小孢子囊在极面观方向分化出两条十字交叉的纵向不育隔膜组织,将其沿花药室纵轴方向深切为4个不等大的棒状次生孢子囊,最后发育为4个花粉团。(2)花药成熟时,靠花药开裂处的隔膜组织比近药隔膜组织的降解速度快且彻底,因此每个药室内的4个花粉团在花药开裂处粘合成一簇。(3)发育完好的花药壁共有6~7层,由外到内为表皮、3~4层药室内壁、中层和双核绒毡层,符合多层型花药壁的发育模式;花药成熟时,表皮退化,纤维性加厚发生在3~4层药室内壁,中层和绒毡层彻底降解。(4)小孢子母细胞通过同时型胞质分裂产生了正四面体型、左右对称、十字交叉型排列的小孢子四分体;小孢子四分体继续保持在同一胼胝质内完成了雄配子体发育,形成了2-细胞型的四合花粉;四合花粉两两或松散或紧密排列,构成了粉质花粉团。在前人的研究基础上,本文证实、补充并分析了竹叶兰属的花粉团发育特征,为该属的亲缘关系提供了胚胎学证据。

Pollinia development in Arundina graminifolia was investigated using paraffin section,including floral anatomy feature,formation patterns of eight pollinia,anther wall development pattern,and microsporogenesis and male gametogensis.The results were as follows:(1)A ripened anther was composed of two thecae containing two clusters of 4-pollinia with a white anther cap.The anther primordium was differentiated into a pair of lateral thecae bending toward the labium.(2)Due to a combination of a cross and a longitudinal sterile septum differentiated in the center of each micrsoporangia,four sub-microsporangia produced and finally developed into four pollinia adherent together at the base by the incomplete degradation of septa.(3)A complete anther wall was composed of 6-7 layers,including an epidermis,3-4 fibrous thickened endothecia,a middle layer,and a bi-nucleated tapetum,which conformed to the massive type.(4)The microspore mother cells produced microspore tetrads through simultaneous cytokinesis,which were arranged in tetrahedral,isobilateral,and decussate types.The microspore tetrads developed into 2-celled pollen tetrads which were grouped into granular pollinia.Some embryological features during pollinia development in A.graminifolia were reconfirmed,supplemented,and emphasized based on the data reported,which could provide better understanding of its generic relationships.