ANATOMICAL AND MICROMORPHOLOGICAL CHARACTERISTICS OF LEAF EPIDERMIS OF SELECTED SPECIES OF <i>Hoya</i> R.BR. (APOCYNACEAE) IN PENINSULAR MALAYSIA

Abstract

Leaf anatomy and micromorphology studies were conducted on ten selected Hoya species in Peninsular Malaysia, namely H. archboldiana C.Norman, H. bhutanica Grierson & D.G.Long, H. glabra Schltr., H. halconensis Kloppenb., H. hanhiae V.T.Pham & Aver., H. limoniaca S.Moore, H. mindorensis Schltr., H. multiflora Blume, H. paziae Kloppenb. and H. pubifera Elmer. This study aims to identify the common characteristics, variations, and diagnostic features of leaf anatomy and micromorphology in the studied Hoya species and to construct a dichotomous key for species identification. This study involved epidermal screening techniques for abaxial and adaxial epidermal observations of leaves, while micromorphological observations involved gold coating, critical point drying, and examination with a scanning electron microscope. Common characteristics observed include the presence and distribution of stomata, leaf margin patterning, and the pattern of anticlinal walls on the leaf's epidermal surface. Variable characteristics include the type of wax, cuticle engraving on the leaf epidermis, structural composition, margin, shape, size, stomatal index, trichomes, leaf margins, starch nodules, and crystals. Diagnostic features identified include the leaf epidermal wax type and starch nodules, the structure of stomata, and trichomes. A dichotomous key for species identification can be developed. This study's results demonstrated that the leaves' anatomical and micromorphological characteristics hold taxonomic significance for identifying, differentiating, and classifying the Hoya species studied.