ULTRASTRUCTURE AND CHEMICAL-COMPOSITION OF SOME ISOLATED PLANT CUTICLES IN RELATION TO THEIR PERMEABILITY TO THE HERBICIDE, DIURON

The ultrastructure of leaf and fruit cuticles from nine species was in vestigated before and after their enzymatic isolation. No major altera tion was observed in the internal ultrastructure of cuticles after the isolation process. The isolated cuticle preparations showed several l evels of complexity from the Pyrus communis L. leaf cuticle represente d by a simple layer, to the Vanilla planifolia Andr. leaf cuticle prep aration having extensive cell walls on its inner face. Two main ultras tructural types were distinguished; cuticles characterized by an almos t entirely reticulate structure and cuticles characterized by an outer lamellate region with an inner reticulate region. The permeability of isolated cuticles to diuron was measured with a double water compartm ent device using C-14-diuron. The permeability coefficient (P) ranged from 1.9 to 40.1 nm s-1 for seven species. The mean value of P for cut icles having an entirely reticulate structure was higher than that for cuticles with an outer lamellate zone. Moreover, for each of the two ultrastructural types, the permeability decreased with an increase in soluble wax content expressed per surface unit.