Epicuticular wax of red mangrove leaves from an urban bay: Chemical composition and micromorphology

This study evaluated the chemical composition of epicuticular wax and micromorphology of Rhizophora mangle L. (red mangrove) leaves collected in mangroves around an urban bay in Rio de Janeiro State, Brazil. Chemical results indicate that epicuticular waxes contain taraxerol, β-amyrin, lupeol and triterpenes acetate as the main compounds. Samples from the Marambaia site were quantitatively different from those collected at Coroa Grande. The content of taraxerol and β-amyrin in leaf waxes from Marambaia was less than 5%, while lupeol (76.62%) was the main compound at this site. Triterpenes of lupane group, such as lupeyl acetate, showed high concentrations in the leaf waxes from typical and hypersaline (salt marsh) areas. We further observed that epicuticular wax varies in shape (crusts, granules or platelets) according to the collection site with a predominant formation of crusts across sites. Energy Dispersive X-Ray Spectroscopy coupled with Scanning Electron Microscopy (EDX-SEM) analysis indicated the presence of Na, Cl, Ca and other elements in the epicuticular wax of leaves from different locations, indicating that R. mangle, a species without secretory salt trichomes, eliminates salts through the leaf surface by permeability conferred by triterpene composition.