ABSTRACT

Identification of Cola species and their long germination time has been a problem. Hence, the aim of this research was to conduct an ecological survey, regeneration and biosystematics studies of Cola species of Southern Nigeria. This research was structured to cover identification exercise, ethnobotanical survey, ecological, regeneration, conservation, morphological, anatomical, chemical and molecular studies of these Cola species. 179 herbarium specimens were studied from Forest Herbarium Ibadan (FHI) and University of Ibadan Herbarium (UIH). Seventeen Cola species found in National Parks (Okomu National Park and Cross River National Parks), forest reserves, secondary forests and homestead in southern Nigeria were inventoried and geo-referenced. C. heterophylla was the only shrub species, while others were trees. All taxa studied were least concern except C. gigas which was a vulnerable species according to the IUCN conservation status. In the ethnobotanical survey; 50 % of the respondents were from southeastern region of Nigeria and 75 % knew only two Cola species (Cola nitida and Cola acuminata) which were identified as gworo and oji Igbo respectively in Igbo language. Only 14.04 % mentioned (bush cola) oji ohia in addition to the two popular Cola species. Weevil/insect and long germination time/slow growth were acknowledged by 40 % and 30.91 % of the respondents respectively to be the major challenges associated with Cola species. Mechanical scarification and soil type had significant effect on the germination time of C. caricaefolia and C. hispida at P ≤ 0.05. Soaking of seed in water caused embryo mortality in C. parchycarpa and C. rostrata seeds while a 24 hours seed soaking was optimum for C. nitida seed with a germination time of 35.33±8.48 days. Mechanical scarification and soaking had no effect on the seedling growth of Cola species but soil type had significant effect on the seedling growth as topsoil or topsoil with carbonized sawdust (TSCSD) proved to be the best sowing medium. However, C. digitata seed failed to germinate. Leaf texture for all taxa were glabrous except for C. gigantea and C. hispida that were scabrous and hispid respectively. Leaf shape varied from elliptic, digitate, lobed, oblanceolate and ovate among the taxa. C. acuminata and C. nitida were amphistomatic while others were hypostomatic. C. gigantea and C. heterophylla had stellate and peltate trichome type. Trichome was completely absent in other taxa. Anomocytic, anisocytic and paracytic stomatal type were observed among the taxa. Alkaloids were absent in all taxa while other metabolities were either present or absent. The GC-MS analysis of the methanolic extract of Cola nitida seeds revealed 14 maximum peaks of which octadecanoic acid, 10-hydroxy-methyl ester was the most abundant compound. C. rostrata and C. parchycarpa contains substantial amount of minerals and vitamins required for nutrition in humans and animals. Four out of five morphologically similar Cola fruits sequenced gave their identity as C. lepidota. Regeneration requirement varied among the species and the groupings obtained from the cluster analysis showed affinity among the species in conformity to the current classification status of the genus.