Heteropyxis natalensis Harv. is a native South African tree used in traditional medicine among Venda and Zulu communities. In this study, micromorphological investigations using light and scanning electron microscopy identified long, tapered non-glandular trichomes on the abaxial and adaxial surfaces of the leaves. The total number of trichomes appeared to be greater on emergent leaves and decreased as leaves matured. In addition, schizolysigenous secretory cavities and druse crystals were found within the leaves. Swollen subdermal secretory cavities were also distributed in the midrib of the leaves. Transmission electron microscopy confirmed the presence of nuclei, plastids, mitochondria, vesicles, rough endoplasmic reticulum cisternae and Golgi bodies in the secretory epithelia of these cavities. Various histochemical tests revealed the presence of alkaloids, phenolics, lipids, proteins, essential oils, resin acids and trace amounts of unesterified pectins and polysaccharides in the leaves. This study provides new findings and contributes to the existing research regarding H. natalensis with respect to the micromorphology, ultrastructure and histochemical composition of this species.
Keywords: Lavender tree; secondary metabolites; secretory cavities; trichomes; ultrastructure.
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