MICROSCOPY OBSERVATIONS ON LEAF EPIDERMAL MICROMORPHOLOGY OF CONGEAROXB. AND SPHENODESME JACK (LAMIACEAE) FROM PENINSULAR MALAYSIA WITH TAXONOMIC IMPLICATIONS
Abstract
The leaf epidermal micromorphology provides important taxonomic characters for distinguishing closely related taxa within the family Lamiaceae. However, information on the micromorphological features of Congea and Sphenodesme species in Peninsular Malaysia remains limited. A micromorphological analysis of the leaf epidermis in five species belonging to the genera Congea and Sphenodesme was conducted to elucidate their generic and infrageneric relationships based on comparative epidermal traits. Microscopic observations were carried out using both light microscopy (LM) and scanning electron microscopy (SEM) to examine leaf micromorphological features, including epidermal cells, stomata, trichomes, and epicuticular wax, in Congea forbesii, C. griffithiana, Sphenodesme racemosa, S. pentandra, and S. triflora. The results showed that C. forbesii was clearly distinguished by its sinuous epidermal cells and amphistomatous leaves, in contrast to the hypostomatous condition observed in the other species. Variation in epidermal sculpturing on both leaf surfaces was recorded, with stomata predominantly flush except in S. racemosa, where they were slightly raised. Paracytic stomata predominated across the examined taxa, although interspecific variation in stomatal type and epidermal sculpturing provided additional diagnostic value. Trichome diversity also proved taxonomically informative, with stellate trichomes occurring uniquely in S. pentandra, while peltate trichomes were consistently present across all species. In addition, epicuticular wax occurred in two distinct morphological forms, namely thin rods and platelets, both contributing supplementary characters of taxonomic significance. These micromorphological traits serve as diagnostic characters for distinguishing Congea and Sphenodesme, further elucidating their taxonomic relationships within the Lamiaceae.
