Leaf anatomy and pollen morphology: sources of additional taxonomic characters in delimiting species of <i>Duboscia</i> Bocq. (Malvaceae S.L.) occurring in parts of southern Nigeria

Abstract

Duboscia is a genus of two species native to tropical Africa. It belongs to the Malvaceae family. The composition of the genus has been a subject of controversy since its establishment. Leaf anatomy and pollen characters of the Duboscia species were investigated using light microscopy with a view to provide additional taxonomic characters in delimiting species boundary in the genus. Dried leaves rehydrated in boiled water were used for the anatomical studies while flow-er buds were used for pollen morphological studies. Epidermal cells were isodiametric, polygonal to irregular with straight to wavy anticlinal cell walls. Leaves were bifacial and hypostomatic with anisocytic and staurocytic stomata types. Pollen grains were small (21.3 – 23.5 μm) and tricolporate. A combination of characters such as type of trichomes, number of glandular trichome head cells in leaves and petioles, shape of the midrib and petiole vascular bun-dle, petiole vascular bundle isolates, petiole outline, number of chlorenchyma cell layers and secretory ducts in midrib and petiole, exine surface, Amb and colpi length can be used as additional taxonomic characters to distinguish the two species and to determine their phylogenetic relationship between related genera in the tribe Grewieae. A key is provided for the identification and delimitation of the species.