Use of foliar and stem anatomical characters in the identification of Ludwigia (Linn.) species in Nigeria

Abstract

Foliar and stem anatomical characters that could be used for the identification of nine species of Ludwigia L. viz., Ludwigia abyssinica A. Rich., L. adscendens subsp. diffusa (Forssk)., L. decurrens variety A Walter., L. decurrens variety B Walter., L. erecta (Linn.) Hara, L. hyssopifolia (G.Don) Exell., L. leptocarpa (Nutt.), L. octovalvis variety brevisepala (Jacq.) Raven and L. octovalvis variety linearis (Jacq.) Raven in Nigeria are reported. This is envisaged to facilitate the management of these Ludwigia species; most importantly the invasive species and also to reduce the fluctuations in their taxonomic classifications. Fresh leaves and matured stem of these nine (9) species of Ludwigia from South-western Nigeria were subjected to anatomical study under Light Microscope. The occurrence of hypoamphistomatic stomata and several other stomata types such as anomocytic, staurocytic, anisocytic, cyclocytic and laterocytic in these advanced species of Ludwigia could be responsible for their invasiveness in the environments. Similarly, the mean vessel diameter in Ludwigia species studied represents invasive character; the species with higher mean vessel diameter are likely to be more invasive in their habits. Baseline information on the stem anatomy of the Ludwigia species has been provided; in addition, diagnostic characters for easy identification and classification of the taxa are also reported. The leaf and stem anatomical characters in the Ludwigia species are constant despite their environmental plasticity.

Keywords: Ludwigia, epidermal, stomata, morphology, diagnostic, invasive.