Permeability of Isolated Eucalyptus gummifera Cuticle Towards Alcohols and Amides

Abstract

The permeability of cuticle isolated from E. gummifera towards a range of aliphatic alcohols and amides was measured in vitro. These compounds were selected to assess the importance of lipoid solubility and molecular size in penetration of cuticle by non-electrolytes. Permeabilities were examined in relation to molecular refractions (as a measure of molecular volume) and oil/water partition coefficients (as a measure of lipoid solubility) of the permeating substances. Results were consistent with the cuticle functioning generally as a lipoid membrane which allows substances to permeate by passive diffusion according to their lipoid solubilities. A molecular sieve model might account rather better for the smallest of the permeating molecules. No asymmetry was observed in regard to inward and outward movement of alcohols or amides.

As a first approximation, the isolated cuticle behaves as a homogeneous lipoid membrane having some aqueous pores.