Anatomical Relationships among Three Species of Curcubitaceae

Anatomical relationship among Citrullus lanatus (Thunb.) Matsum. & Nakai, Cucumeropsis mannii Naudin and Lagenaria siceraria (Molina) Standl planted in controlled conditions in the Botanical garden of the University of Calabar were determined. Standards anatomical (transverse) sections of the leaves were prepared and photo micro graphed. Generalized transverse sections of the leaf, stomata and trichome were studied. The result showed a single layer of epidermal cells, a thick cuticle on both leaf surfaces, presence of hairs and the occurrence of collenchymatous tissues along the median line of the upper surface of each leaf midrib. The palisade parenchyma consists of 2 to 3 layers of elongated, cylindrical cells which are closely packed together in all the species while the spongy parenchyma are loosely arrange with numerous intercellular spaces and are irregular in shape in all species. The vascular bundles in all the species are bicollateral but are differentially arranged depending on species. Anatomy of the leaf section reveals the presence of anomocytic stomata in all three species. The stoma was observed as completely surrounded by four to six variable shapes and sizes of subsidiary cells. The cells surrounding the stoma are quite alike to the remaining epidermal cells except among the subsidiary cells surrounding the stoma. The subsidiary cells are four (4) in L. siceraria, five (5) in C. mannii and variable (4-6) in C. lanatus. The trichome of all three species is multicellular and unbranched (uniseriate). However the shape is conical in L. siceraria and C. mannii but clavate in C.lanatus. The number of cells in the trichome varies from 2-3 in C. lanatus and 3-4 in L. siceraria and C. C. mannii. While there are ridges on the trichome of L. siceraria the terminal cell in all three species tapers. When these data were converted to numerical taxonomy using Euclidean distance, L. siceraria was observed as the out group with C. mannii and C.lanatus exhibiting about 83.3% and 66.3% shared apomorphies. The differences proved statistically significant at 0.05 confidence limit. Thus the use of anatomical evidence disagrees on the lumping of these species into one genus.