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

Leaf trichome morphology and density are described for three species belong ing to the genus Trema from West Africa: T. africana (Planch.) Blume, T. or ientalis (L.) Blume, and T. nitens (Hook. & Planch.) Blume. Leaves of speci mens collected in West Africa were observed using scanning electron microsc opy. Unicellular trichome morphology was assessed, and a 3 + 3 two-way cont ingency table analysis showed dependence between the trichome type and spec ies identity. Density of unicellular and multicellular trichomes on both le af surfaces as well as the number of cells composing the stalk of multicell ular trichomes were measured and subjected to nonparametric analysis of var iance. Kruskal-Wallis tests yielded significant results (p < 0.05) among th e three species for all characters except unicellular trichome density on t he adaxial leaf surface. Wilcoxon two-sample tests showed that all species were different, except for the density of multicellular trichomes on the ab axial leaf surface where densities in T. africana and T. orientalis were no t significantly different. The number of cells composing the stalk of multi cellular trichomes was significantly different among each species on the ad axial leaf surface, but on the abaxial one, T. africana and T. orientalis e xhibited no significant differences. The value of these characters in the d iscrimination between the three species is discussed.