Morphological and histochemical characterization of the secretory sites of bioactive compounds in leaves of Lantana camara L. (Verbenaceae)

Abstract

Lantana camara L. is a species of Verbenaceae known for its aromatic and medicinal properties. Compounds extracted from its leaves are used to treat infections of the respiratory tract and have demonstrated antimicrobial potential and repellent action to Aedes mosquitoes. Our aim was to identify and characterize the main production sites of the biologically active substances in the leaf blades of L. camara. Leaf samples were collected from plants living in the Brazilian Cerrado and processed according to standard techniques in plant anatomy and histochemistry as well as scanning and transmission electron microscopy. Six morphotypes of glandular trichomes (I-VI) were identified; they differ in shape and size, number of constituent cells, subcellular aspects, and form of accumulation, as well as release and composition of the secretion. Idioblasts producing hydrophilic and lipophilic substances were observed in the mesophyll and may be associated with protection of the plant against herbivores and pathogens and maintenance of the water potential of leaf tissues, complementing the action of glandular trichomes. Our results contribute to the understanding and knowledge of the sites responsible for the production of substances with ecological and medicinal value in Verbenaceae species, and may provide a foundation for future studies in different areas of science focusing on the manipulation of this production.