Morpho-Anatomical Studies of Gnetum africanum Welw and Gnetum buchholzianum Engl. (Gnetaceae Lindley) in Nigeria

Abstract

A comparative study aimed at providing detailed morpho-anatomical information on two species of Gnetum found in Nigeria was carried out. The species are of high nutritive importance and taxonomic information on them is scanty. The species are Gnetum africanum Welw. and Gnetum buchholzianum Engl. These are the only species of Gnetum found in Nigeria in particular and Africa in general. Gnetum, belonging to the family Gnetaceae, a gymnosperm, is a tropical genus which occurs in Asia, Africa and South America. Members of this genus are mostly climbers, shrubs or small trees. The leaves are borne only on shoots of limited growth and are large, oval, entire, with net venation making the plant look like an angiosperm. Hand sections of the stem, leaf, and petiole were made and photographs taken with a Leitz Diaplan photomicroscope fitted with Leica WILD MPS 52 camera. Features of taxonomic value include presence of accessory transfusion tissue in the leaves, brachysclereids in the stem, leaf and petiole, druses and prisms in the petiole, astrosclereids in the stem and leaf. The morphological features of interest include variations in the shape, sizes and colour of leaves and character of the male reproductive parts. In conclusion, it can be stated based on the result of this work that this two species of Gnetum are very closely related anatomically based on the fact that there was little variation in their stem, petiole and leaf anatomy. The work is however not conclusive. More investigations especially in cytogenetics and phytochemistry may provide relevant information to authenticate the classification of these species.