中国桑寄生科植物叶表皮微形态

通过扫描电镜对中国桑寄生科桑寄生亚科8属18种和槲寄生亚科1属2种植物成熟叶的上、下叶表皮内表面和下表皮外表面进行了研究。内面观发现桑寄生科植物叶上、下表皮形状为多边形,垂周壁式样平直或稍弓形,常具有角质增厚,平周壁常覆盖厚角质或颗粒状、丝状角质增厚;气孔存在于上下表皮,通常下表皮较多,气孔的形状,特别是保卫细胞的形态在亚科间、属间或种间都具有一定的差异,气孔器类型为平列型或单圈型。下表皮表面观察了的角质膜和蜡质纹饰、气孔的形状,外部气孔缘及外部气孔缘内缘的特征。这些特征在亚科或属级水平上较为稳定,有的也表现出种间差异,有一定的分类价值。从气孔形态和外部气孔周围角质膜来看,两亚科显示出明显的不同:桑寄生亚科上、下表皮均具有内部气孔缘,而槲寄生亚科没有此结构;桑寄生亚科外部气孔周围角质膜增厚成环状,其上具增厚的条纹,而槲寄生亚科外部气孔周围角质膜增厚成脊状,不具条纹。这些特征支持槲寄生亚科作为独立1个科来处理。

Micromorphology of leaf epidermis in Chinese Loranthaceae

The inner surfaces of both the upper and lower epidermal cells and the outer surface of the lower epidermis of mature leaves in 20 species belonging to 9 genera and 2 subfamilies(Loranthaceae)were observed under SEM. It is found that viewed from the inner surfaces of both upper and lower epidermis, the cells are tetragonal or pentagonal;the anticlinal walls are straight,arched,and usually thick;the periclinal walls usually have thick cuticular membrane,or sometimes with granular and filiform cuticular;the stomatas are mainly distributed on the lower epidermis,and with fewer on the upper epidermis. Shapes of the stomata,especially of their guard cells,are different between subfamilies and among genera. The stomatal apparatuses are'paracytic and/ or pericytic. In the outer surface of the lower leaf epidermis of the family,characteristics of the cuticular membrane, waxy ornamentation,shapes of stomatas,outer stomatal ledge(or rim)and inner margin of outer stomatal ledge(or rim)were observed. These characteristics exhibited a great diversity in the family,or even within a genus in some cases,although it is generally stable at subfamily or generic level. Therefore,SEM characters of the outer surface of leaf epidermis are of certain taxonomic significance. The morphology of the stomata and the cuticular membrane surrounding the stomata are distinguishable between subfamilies. Loranthoideae usually have inner stomatal ledges that were not observed in the Viscoideae;the cuticular membrane surroundingthe stomata in the outer surface of leaf epidermis is annular and striate in Loranthoideae, but ridged in Vis-coideae. These characters support the familial status of Viscoideae.