Plant Cuticular Waxes: Composition, Function, and Interactions with Microorganisms

Abstract

The interface between leaves and the surrounding environment is formed by the wax-covered plant cuticle, which is hydrophobic and highly impermeable to water and dissolved solutes. The surface itself may become superhydrophobic by com- plex three-dimensional wax crystals. There is evidence that this system evolved already early with the colonization of land some 450 million years ago. Although the leaf surface represents a hostile environment, because water and nutrient availability is very limited and variations in temperature and light intensity can be quite large, it forms the habitat for specialized epiphyllic microorganisms successfully colonizing the leaf surface which is also called phyllosphere. Certain strategies improving living conditions within the phyllosphere have been devel- oped by epiphyllic microorganisms. They can significantly enhance leaf surface wetting and water permeability of the hydrophobic cuticle. This interaction significantly increases the abundance of water on the leaf surface, and as a consequence, leaching of nutrients to the leaf surface should be increased, thus becoming available for epiphyllic microorganisms. This strategy is supported by the ability of biosurfactant production, which represents a common and important adaptation of epiphyllic microorganisms.