A simple photometric device analysing cuticular transport physiology: surfactant effect on permeability of isolated cuticular membranes of Prunus laurocerasus L

4-Nitrophenol permeabilities of astomatous cuticular membranes isolated from the upper surface of Prunus laurocerasus L. leaves were measured applying a newly developed photometric device. Isolated cuticles were mounted between donor and receiver compartments of a stainless steel transport chamber. 4-Nitrophenol was applied as non-dissociated species in citric buffer at pH 3.0 in the donor compartment and sampled as dissociated species in the receiver compartment in borate buffer at pH 9.0. Permeances, calculated from steady-state rates of 4-nitrophenol permeation, ranged from 1.73 X 10(-10) m s-1 up to 38.4 X 10(-10) m s-1. They were in the same order of magnitude compared to published permeances obtained with a different method using radiolabelled 4-nitrophenol and isolated cuticles of Citrus aurantium L. In the presence of the surfactant Brij 30, which is a polydisperse alcohol ethoxylate, cuticular permeabilities increased on average by a factor of 37. Cuticles, initially having the lowest permeabilities, exhibited the highest increase of their permeabilities due to the surfactant and vice versa. This increase of cuticular permeabilities in the presence of a surfactant is interpreted as a plasticizing effect of the surfactant molecules on the cuticular wax forming the cuticular transport barrier. Furthermore, surfactant-induced increases of cuticular permeabilities were reversible to a large extent. Permeabilities decreased again after the removal of Brij 30 reaching final values about 6-times higher compared to the initial permeabilities. This demonstrates that the surfactant and the permeating molecule must be present simultaneously in the cuticle in order to enhance cuticular permeation. Possible applications of this simple photometric device analysing further aspects of cuticular transport physiology are finally suggested.