Transport properties of cuticular waxes ofFagus sylvaticaL. andPicea abies(L.) Karst.: Estimation of size selectivity and tortuosity from diffusion coefficients of aliphatic molecules

摘要

Diffusion coefficients for thirteen lipophilic organic compounds in reconstituted waxes ofFagus sylvaticaL. andPicea abies(L.) Karst. were measured to characterise the transport properties of the cuticular waxes that form the transport-limiting barrier of plant cuticles. Desorption kinetics (relative amounts desorbed versus time) were asymptotic, but could be linearized up to 50 desorption by plotting relative amounts desorbed versus the square root of time. Diffusion coefficients calculated from the slopes of the linear regressions ranged from 10−22to 10−17m2·s−1and decreased with increasing molecular size. This size dependency of diffusion coefficients was analysed, assuming an exponential dependence of the diffusion coefficients on molar volumes, which allowed cuticular transport properties to be related to the physical structure of the wax. Furthermore, the fact that the barrier properties ofFaguswax are less pronounced than those ofPiceais interpreted as an ecological adaptation of the respective tree species to their habitats at the level of their cuticular transport ba