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 investigated before and after their enzymatic isolation. No major alteration was observed in the internal ultrastructure of cuticles after the isolation process. The isolated cuticle preparations showed several levels of complexity from the Pyrus communis L. leaf cuticle represented by a simple layer, to the Vanilla planifolia Andr. leaf cuticle preparation having extensive cell walls on its inner face. Two main ultrastructural types were distinguished; cuticles characterized by an almost 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 compartment 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 cuticles 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.