Characters of the leaf epidermis of Stemonaceae and their taxonomical significance

The micromorphology of the leaf epidermal surfaces of 30 Stemonaceae species from four genera were observed using light microscopy and scanning electron microscopy. Results showed that both the adaxial and abaxial epidermal cells were polygonal or irregular in shape, with undulate, straight, or arched anticlinal walls. The leaf epidermal characteristics of most species were amphistomatic, though some were hypostomatic or hyperstomatic. The micromorphology of the epidermal cuticle sculpture ornamentation was diversified. Most species had no hairs covering the leaf surface, though some species had unicellular hairs on both the upper and under epidermis. The stomatal apparatus was mainly distributed on the under epidermis of the leaves, except for Stemona prostrata I. R. H. Telford, S. cochinchinensis Gagnep, S. rupestris Inthachub, S. pierrei Gagnep, and S. involuta Inthachub, which had stomatal apparatus on both the upper and under epidermis. The stomata type was anomocytic in all observed species and the stoma were oval in shape. Definite evolution regularity was found in the micromorphological characteristics of the epidermis of the leaves of Stemonaceae among genera, but no clear regularity was detected within genus, implying that the family might be a natural monophyletic group. Considering the difficulty of sampling, and in the absence of a phylogenetic tree, these micromorphological characteristics may provide new evidence for the taxonomy, biogeography, and ecological adaptability of Stemonaceae.