瘤足蕨属(Plagiogyria)植物叶柄和羽片横切面解剖学特征及分类学意义

Anatomical characteristics and taxonomic significance from transverse sections of petiole and pinnule of Plagiogyria

该文采用光学显微镜,首次对九种瘤足蕨属植物的叶柄和羽片横切面进行了解剖学比较研究。结果表明:九种瘤足蕨属植物在叶柄中部横切面的表皮、基本组织和中柱以及营养叶羽片的表皮、叶肉和主脉等结构特征是相似的,如叶柄中部横切面的表皮不被毛或是鳞片,表皮细胞形状呈类圆形,具有厚壁组织,中柱为周韧型维管束;营养叶羽片横切面的气孔只分布于下表皮,表皮细胞形状呈扁平状,主脉的结构类型属于周韧型维管束。在系统的演化中,瘤足蕨与桫椤科植物有一定的亲缘关系,两者既有相似的特征但也表现出一定的差异,支持瘤足蕨属是一个自然分类的观点。九种瘤足蕨属植物叶柄中部横切面形状有梯形、椭圆形和三角形,叶柄中部横切面维管束的形状成"U"字形、"V"字形或"品"字形;维管束数目1个或3个;维管束结构中的木质部成"八"字形、"U"字形或"一"字形;羽片主脉下侧形成了以三角形、弧形或梯形的突起;叶柄中的木质部形态有两种,即典型的海马形状以及非典型的海马形状,其中典型的海马形状的特点为叶柄的木质部两侧都呈现弯曲成钩的形态,非典型的海马形状特点为2个木质部束的两侧都未出现弯曲成钩的形态或者是其中的一个木质部一端无弯曲成钩的形态,这些形态解剖特征稳定且具类群特异性,为瘤足蕨属植物的分类和系统学研究提供了新的依据。同时,依据其叶柄和羽片横切面解剖叶柄学特征列出了瘤足蕨属植物分种检索表。

The anatomical comparative study of petiole and pinnule cross-sections of nine species from Plagiogyria was performed using light microscopy for the first time.The results showed that the epidermis,the basic tissue and middle column of middle petiole transection and epidermis,mesophyll and main vein of the vegetative leaf pinnule of nine species of Plagiogyria were similar,for example,the epidermis of the transverse section of the middle petiole was not covered with hair or squamas,the epidermis was round in shape with thick-walled tissue,and the central cylinder was a amphicribral vascular bundle;the stomatas of trophyll pinnule transection were only distributed in the lower epidermis,the shape of epidermal cells was flat,and the type of the main vein belongs to the peripheral vascular bundle,which supports for the viewpoint that Plagiogyria was a natural taxonomy.In the evolution of the system,Plagiogyria had a certain relationship with the Alsophila spinulosa and both of them had similar characteristics and also showed certain differences.However,the petiole central transverse section of these nine species of Plagiogyria were trapezoidal,oval or triangular.The shape of the vascular bundle including“U”shape,“V”shape or triangle.The number of vascular bundles in the central transverse section of the petiole was one or three.The arrangement of xylem in vascular bundles including Chinese character“Eight”shape,“U”shape or“-”shape;The underside protuberances of the pinnule main veins were curved,triangular or trapezoidal.The xylem of the petiole had two forms:typical hippocampus and atypical hippocampus.The typical hippocampus was characterized by obvious hook state at both ends of the xylem.The atypical hippocampus was characterized by no obvious hook state at the two ends of xylem or one of the xylems had no hook at one end.These morphological anatomical features are stable and cluster specific,which provides a new reference for taxonomy and systematic studies of Plagiogyria.Finally,a key to the Plagiogyria species is given based on the anatomical characteristics of the transverse section of petiole and pinnule.