中国罗汉松属叶角质层微形态结构及其分类意义

Cuticle Micromorphology of Podocarpus from China and Its Taxonomic Significance

利用扫描电镜对罗汉松属8种2变种植物叶角质层内外表面进行了细致观察。发现罗汉松属植物叶角质层结构具有许多相似特征,表皮细胞较为规则,长方形或多边形,边缘波状弯曲;气孔器排列成带状,长轴均与叶脉一致,气孔器具较为明显的气孔塞和伏罗林环,气孔器保卫细胞极延伸明显,通常具有2～4个副卫细胞、不具极副卫细胞。但罗汉松属叶角质层结构也具有明显的种间差异,镰叶罗汉松和洛杉矶罗汉松同其它种类差异最大,这两种植物叶两面均具气孔器,角质层内表面垂周壁直,角质层凸缘不明显;贺氏罗汉松最为显著的特征是近轴面和远轴面表皮细胞的垂周壁角质层厚且凸缘均极其发达;小叶罗汉松近轴面表皮细胞排列较为规则,多数为方形,长轴与叶脉垂直,垂周壁之间的角质层突起较为显著,延伸到皮下层;兰屿罗汉松近轴面表皮细胞排列较不规则,多边形,细胞的角端比较钝,没有棱角;大理罗汉松气孔带间隔较小,有时两条气孔带挤在一起,使副卫细胞紧连,近轴面表皮细胞较短,方形或长方形,垂周壁之间的角质层较不发达;海南罗汉松角质层气孔带间隔较宽,气孔器形状为阔椭圆形,近轴面表皮细胞均为细长方形;变种短叶罗汉松和狭叶罗汉松与罗汉松也具有明显差异,短叶罗汉松近轴面表皮细胞排列不规则,垂周壁深波状弯曲,凸缘极为明显,但原种罗汉松近轴面表皮细胞排列较为规则,垂周壁浅波状弯曲,凸缘不明显,而狭叶罗汉松近轴面表皮细胞方形或长方形,比罗汉松的表皮细胞短,垂周壁直或略弯曲,角质层极厚。这些角质层微形态特征差异可以作为罗汉松属内种类分类鉴定的依据。

We studied the cuticle micromorphology of leaves from 8 species and 2 varieties of Podocarpus with scanning electron microscopy. The leaf epidermal structures of Podocarpus revealed remarkable consistency.Epidermal cells are rectangular or irregular in shape,the outlines of epidermal cells are slightly undulating with prominent butresses. The stomata are oriented parallel to the long axis of the leaf. Floring rings and stomatal plugs are usually present. The guard cells have prominent polar extension and stomata usually have two to four subsidiary cells,often with polar subsidiary cells lacking. However,there are more or less discrepancies in the arrangement of stomatal apparatus,the shape of epidermal cells within these species. In P. falcatus and P. gracilior,stomatal apparatus distributes on both surfaces,cuticle flanges on epidermal cells are straight and without buttress. In other taxa,stomatal apparatus is only restricted to abaxial surfaces. On both adaxial and abaxial surfaces,the cuticle flanges on epidermal cells in P. henkelii are thick and with prominent buttresses. In P. wangii,the epidermal cells of adaxial surfaces are fairly regular,most cells are tetragonum and perpendicular to the long axis of leaf vein,the cuticle flanges are more prominent and extending to the hypodermis. In P. costalis,the adaxial epidermal cells are irregular and polygonous. In P. forrestii,the stomatal intervals are less and the adaxial epidermal cells are shorter,the cuticle flanges are less pronounced. In P. annamiensis,the stomatal intervals are relatively wide,the stomata exhibit broad elliptic,the epidermal cells of adaxial surfaces are thin rectangle in outline. In addition, the shape of epidermal cells on both surfaces and buttress characteristics in P. macrophyllus var. maki and P. macrophyllus var. angustifolius are distinctly different from those in P. macrophyllus. The epidermal cells of adaxial surfaces in P. macrophyllus var. maki are irregular and sinuate in outline,the flange between epidermal cells are fairly thick. In P. macrophyllus var. angustifolius,the epidermal cells of adaxial surfaces are square to rectangular, in outline, often shorter than those in P. macrophyllus,and the flange between epidermal cells are thicker than that in P. macrophyllus. Therefore,these differences of cuticle micromorphology may be used to distinguish species or variety in Podocarpus.