| Abstract: | 4-Nitrophenol permeabilities of astomatous cuticular membranesisolated from the upper surface of Prunus laurocerasus L. leaveswere measured applying a newly developed photometric device.Isolated cuticles were mounted between donor and receiver compartmentsof a stainless steel transport chamber. 4-Nitrophenol was appliedas non-dissociated species in citric buffer at pH 3.0 in thedonor compartment and sampled as dissociated species in thereceiver compartment in borate buffer at pH 9.0. Permeances,calculated from steady-state rates of 4-nitrophenol permeation,ranged from 1.73 10–10 m s–1 up to 38.410–10ms–1. They were in the same order of magnitude comparedto published permeances obtained with a different method usingradiolabelled 4-nitrophenol and isolated cuticles of Citrusaurantium L. In the presence of the surfactant Brij 30, whichis a polydisperse alcohol ethoxylate, cuticular permeabilitiesincreased on average by a factor of 37. Cuticles, initiallyhaving the lowest permeabilities, exhibited the highest increaseof their permeabilities due to the surfactant and vice versa.This increase ofcuticular permeabilities in the presence ofa surfactant is interpreted as a plasticizing effect of thesurfactant molecules on the cuticular wax forming the cuticulartransport barrier. Furthermore, surfactant-induced increasesof cuticular permeabilities were reversible to a large extent.Permeabilities decreased again after the removal of Brij 30reaching final values about 6-times higher compared to the initialpermeabilities. This demonstrates that the surfactant and thepermeating molecule must be present simultaneously in the cuticlein order to enhance cuticular permeation. Possible applicationsof this simple photometric device analysing further aspectsof cuticular transport physiology are finally suggested. Key words: Cuticular transport, leaf surface, permeability, plant cuticle, surfactant |
