Movement and regeneration of epicuticular waxes through plant cuticles

Regeneration of plant epicuticular waxes was studied in 24 plant species by high-resolution scanning electron microscopy. According to their regenerat ion behaviour, four groups could be distinguished: (i) regeneration occurs at all stages of development; (ii) regeneration occurs only during leaf exp ansion; (iii) regeneration occurs only in fully developed leaves; (iv) plan ts were not able to regenerate wax. Wax was removed from the leaves with wa ter-based glue and a liquid polymer, i.e. water-based polyurethane dispersi on. In young leaves these coverings could not be removed without damaging t he leaves. After a few days, waxes appeared on the surface of these polymer films, which still adhered to the leaves. It is concluded that waxes move through the cuticle in a process similar to steam distillation. This hypoth esis could be further substantiated in refined in vitro experiments. Wax is olated from Eucalyptus globulus was applied to a filter paper, subsequently covered with a liquid polymer and fixed onto a diffusion chamber filled wi th water. The diffusion chamber was put into a desiccator. After 8-10 days at room temperature, crystals similar in dimensions and shape to in situ cr ystals appeared on the surface of the polyurethane film. This indicates tha t waxes in molecular dimensions move together with the water vapor that per meates through the polymer membrane. Based on these results, we propose a n ew and simple hypothesis for the mechanism of wax movement: the molecules t hat finally form the epicuticular wax crystals are moved in the cuticular w ater current.