Taxonomic Significance of Leaf Epidermal Attributes of some Herbaceous Species of Euphorbia L. (Euphorbiaceae) in Nigeria

Foliar epidermis of six species of Euphorbia Linn. in Nigeria was studied with the aim of ascertaining reliable characters for easy identification, delimitation and indicating relationships among species. Light microscopy was employed to evaluate leaf surface features such as shape of epidermal cell, stomata and trichome and their distribution frequency. Epidermal shapes are variable i.e. polygonal, irregular and undulate. Stomatal complex types include anomocytic, anisocytic, paracytic, diacytic were encountered. Diacytic stomatal complex was observed only in E. heterophylla and E. thymifolia; anomocytic, anisocytic, paracytic and diacytic in E. heterophylla; Euphorbia hirta has anomocytic, anisocytic and paracytic stomata while E. graminea has paracytic, anomocytic and anisocytic stomatal complexes. All the six examined species are amphistomatic. Trichomes are widespread in the representative species except for E. hyssopifolia which has no trichome. Observed foliar trichomes were non-glandular, unicellular and multicellular with swollen base in the examined species. The distinguishing shape and size of epidermal cell, anticlinal cell wall pattern, guard cell size, stomata type and trichome type varied among species. Similarities in leaf anatomical structures indicate interspecies relationships and this justify their grouping in the same genus. A dichotomous bracketed key to the Euphorbia species is provided.