Nanostructure of epicuticular plant waxes: Self-assembly of wax tubules

A “surface science approach” is used to investigate the growth process of tubular wax structures on plant leaves: natural epicuticular wax from nasturtium leaves, mainly consisting of (S)-nonacosan-10-ol, has been recrystallized on artificial substrates of different structure and polarity, namely HOPG, glass and silicon oxide, and the growth process and structure have been studied with scanning electron microscopy (SEM) and atomic force microscopy (AFM). As a result the tubular structure as found on the living leaves is reproduced independent of the nature of the substrate and the way of wax deposition. Prerequisite for tubule formation, however, is the admixture of a few percent of alkyl-diols to the nonacosan-10-ol as shown with artificial mixtures of both components.