Leaf trichome morphology and density in West African Trema spp. (Ulmaceae: Celtidoideae)

Abstract

Leaf trichome morphology and density are described for three species belonging to the genus Trema from West Africa: T. africana (Planch.) Blume, T. orientalis (L.) Blume, and T. nitens (Hook. & Planch.) Blume. Leaves of specimens collected in West Africa were observed using scanning electron microscopy. Unicellular trichome morphology was assessed, and a 3 × 3 two-way contingency table analysis showed dependence between the trichome type and species identity. Density of unicellular and multicellular trichomes on both leaf surfaces as well as the number of cells composing the stalk of multicellular trichomes were measured and subjected to nonparametric analysis of variance. Kruskal-Wallis tests yielded significant results (p < 0.05) among the three species for all characters except unicellular trichome density on the adaxial leaf surface. Wilcoxon two-sample tests showed that all species were different, except for the density of multicellular trichomes on the abaxial leaf surface where densities in T. africana and T. orientalis were not significantly different. The number of cells composing the stalk of multicellular trichomes was significantly different among each species on the adaxial leaf surface, but on the abaxial one, T. africana and T. orientalis exhibited no significant differences. The value of these characters in the discrimination between the three species is discussed.Key words: Trema spp., Ulmaceae, West Africa, leaf trichomes, morphology, density.