SORPTION AND DIFFUSION OF C-14 ATRAZINE THROUGH ISOLATED PLANT CUTICLES

Sorption and penetration of atrazine through plant cuticles were inves tigated using enzymatically isolated tomato and pepper fruit cuticles. Sorption was rapid and equilibrium was reached within 4 - 6 hours for the two species. Mean values fdr cuticle/water partition coefficients (K-cw) were 140 and 131 for pepper and tomato cuticles, respectively. Sorption was not affected by pH solution between 3.5 and 8 but it was reduced at pH 1.7. The amount sorbed (nmol mg(-1)) varied linearly wi th concentration from 1.3 mu M to 0.1 mM. Atrazine was reversibly sorb ed to cuticles and only 1 to 4% was still retained by cuticles after 4 8 hours washing. Diffusion of atrazine through cuticles increased line arly with time. Permeability coefficient values determined at 0.1 mM a trazine were 24.6 and 47.3 nn s(-1) for pepper and tomato fruit cuticl es, respectively. Comparison with simazine showed that the cuticle/wat er partition coefficient was markedly lower for this herbicide. K-cw w as 48.4 and 46.2 for pepper and tomato cuticles, respectively. Diffusi on of simazine through cuticles was also lower particularly for pepper cuticles. Copyright (C) 1996 Elsevier Science Ltd.