Foliar Epidermal and Pollen Characters of Some Species in the Genus Microcos Linn. in Nigeria

Abstract

Microcos Linn. (Malvaceae s.l) is a genus made up of about 60 spp. distributed in Asia and Tropical Africa. In West Africa, 8 species have been recorded of which six species have been documented for Nigeria to occur in lowland rainforest. This study is designed to carry out preliminary foliar epidermal and pollen morphological studies with a view to advance the understanding of the taxonomic relationship between and among species in the genus using the Nigerian taxa. The foliar epidermal and pollen characters were investigated by light microscopy. The epidermises are composed of isodiametric, polygonal or irregular cells. Anticlinal walls are straight, curved or un-dulate. All taxa are hypostomatic with anisocytic, paracytic and staurocytic stomata types. The mean stomatal size varies from 13.8 × 13.5 μm in M. barombiensis to 16.0 × 18.0 μm in M. coriacea. The dense distribution of stellate trichomes on the abaxial surface of M. malacocarpa and the absence of crystals in M. oligoneura are diagnostic for these taxa. The pollen grains are small in size (10-25 μm), tricolporate with short colpi, subprolate or prolate. Mean colpi length varies from 15.7 μm in M. iodocarpa to 17.5 μm in M. malacocarpa. The ora size varies from 5.4 μm in M. barombiensis to 12.5 μm in M. malacocarpa. The ambient and ora size are significant in the delimitation of the studied taxa. The two groups obtained from epidermal and pollen characters correlate with those earlier obtained from morphological data.