关键词: 罗汉松属, 角质层微形态, 分类意义

Abstract: 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.

Key words: Podocarpus, cuticle micromorphology, taxonomic significance