Gas permeability of plant cuticles

摘要

Cuticles from the adaxial surface ofCitrus aurantiumL. leaves and from the pericarp ofLycopersicon esculentumL. andCapsicum annuumL. were isolated enzymatically and their oxygen permeability was determined. Isolated cuticles were mounted between a gaseous and an aqueous compartment with the physiological outer side of the membrane facing the gaseous compartment. Permeability for oxygen was characterized by permeability (P) and diffusion (D) coefficients. P and D were independent of the driving force (gradient of oxygen concentration) across the cuticle, thus, Henry's law was obeyed. P values for the diffusion of oxygen varied between 3·10-7(Citrus), 1.4·10-6(Capsicum), and 1.1·10-6(Lycopersicon) m·s-1. Extraction of soluble lipids from the cuticles increased the permeability. By treating the cutin matrix and the soluble lipids as resistances in series, it could be demonstrated that the soluble lipids were the main resistance for oxygen permeability inCitruscuticles. However, inLycopersiconandCapsicum, both the cutin matrix and the soluble lipids determined the total resistance. P values were not affected by either the proton concentration (pH 3–9) or the cations (Na+, Ca2+) present at the morphological inner side of the cuticles. It is concluded that the water content of cuticles does not affect the permeability properties for oxygen. Partition coefficients indicated a high solubility of oxygen in the cuticle ofCitrus. The data suggest a solubility process in the cuticle ofCitruswith respect to oxygen perme