A SIMPLE PHOTOMETRIC DEVICE ANALYZING CUTICULAR TRANSPORT PHYSIOLOGY - SURFACTANT EFFECT ON PERMEABILITY OF ISOLATED CUTICULAR MEMBRANES OFPRUNUS-LAUROCERASUS L

4-Nitrophenol permeabilities of astomatous cuticular membranes isolate d from the upper surface of Prunus laurocerasus L. leaves were measure d applying a newly developed photometric device. Isolated cuticles wer e mounted between donor and receiver compartments of a stainless steel transport chamber. 4-Nitrophenol was applied as non-dissociated speci es in citric buffer at pH 3.0 in the donor compartment and sampled as dissociated species in the receiver compartment in berate buffer at pH 9.0. Permeances, calculated from steady-state rates of 4-nitro- pheno l 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 publishe d permeances obtained with a different method using radiolabelled 4-ni trophenol 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. Cut icles, initially having the lowest permeabilities, exhibited the highe st increase of their permeabilities due to the surfactant and vice ver sa. This increase of cuticular permeabilities in the presence of a sur factant is interpreted as a plasticizing effect of the surfactant mole cules on the cuticular wax forming the cuticular transport barrier. Fu rthermore, surfactant-induced increases of cuticular permeabilities we re reversible to a large extent. Permeabilities decreased again after the removal of Brij 30 reaching final values about 6-times higher comp ared to the initial permeabilities. This demonstrates that the surfact ant and the permeating molecule must be present simultaneously in the cuticle in order to enhance cuticular permeation. Possible application s of this simple photometric device analysing further aspects of cutic ular transport physiology are finally suggested.