caa a22 4500 477101496 CHVBK 20180405111542.0 cr unu---uuuuu 170330e19960701xx s 000 0 eng 10.1007/BF00195732 doi (NATIONALLICENCE)springer-10.1007/BF00195732 Mobilities of organic compounds in plant cuticles as affected by structure and molar volumes of chemicals and plant species [Elektronische Daten] [Peter Baur, Hend Marzouk, Jörg Schönherr, Hubert Bauer] Solute mobilities of 28 compounds in isolated cuticular membranes (CM) from Capsicum annuum L. fruit, Citrus aurantium L. and Pyrus communis L. leaves were studied using unilateral desorption from the outer surface. First-order rate constants of desorption (k*), which are directly proportional to the diffusion coefficient in the waxy outer limiting skins of cuticles were measured. When log k* was plotted vs. molar volumes of test compounds linear graphs were obtained. The y-intercepts of these graphs (k*∘) represent the mobility of a hypothetical molecule having zero molar volume and the slopes of the graphs (β′) represent the size selectivity of the barrier and are related to the free volume available for diffusion. Thus, solute mobilities in cuticles are composed of two independent terms which are subtractive. If k*∘ and β′ are known, k* can be estimated for any solute from its molar volume (Vx) using the equation log k*=log k*∘ −β′Vx. These parameters were used to analyse the effects of plant species, extraction of cuticular waxes and molecular structure of solutes on solute mobilities in plant cuticles. For aliphatic solutes, k*∘ was a factor of 10 smaller than for cyclic compounds, while β′ was 0.011 and 0.012, respectively. The k*-values for CM of the three species were very similar, but β′ was higher for bitter-orange CM (0.012) than for those of pepper fruits and pear leaves (0.009). This has the consequence that differences in solute mobilities (k*∘) among cuticles from different plan species increase with increasing molar volumes of solutes. Our data and our analysis provide evidence that constituents of cuticular waxes are mobile, at least in the solid amorphous wax fraction, but mobility decreases rapidly with increasing molar volume. For instance, if β′ amounts to 0.01, mobilities of wax monomers decrease by a factor of 10 for every increase in molar volume of 100 cm3 · mol−1. Thus, hexadecanoic acid is quite mobile in the amorphous wax fraction of Citrus (k*=1.5×10−6·s−1), but for dotriacontane having twice the molar volume, k* was only 2.5×10−9·s−1, which is almost three orders of magnitude smaller. Wax esters have even higher molar volumes and their mobilities will be even smaller (about 4×10−12·s−1 for a C48-ester). Since low chain mobilities are a prerequisite for low mobilities and permeabilities, the selective advantage of high-molecular-weight wax monomers in plant cuticular waxes becomes obvious. Extracting cuticular waxes from pear leaf CM increased solute mobilities by a factor of 182, but it had no effect on size selectivity. We interpret this result as evidence to the effect that cuticular waxes reduce mobility by increasing tortuosity of the diffusion path, rather than by decreasing the mean free path of diffusional jumps and jump frequencies of diffusants. Springer-Verlag, 1996 Apparent diffusion coefficients nationallicence Capsicum nationallicence Citrus nationallicence Cuticular waxes nationallicence Pyrus nationallicence Tortuosity nationallicence CM : cuticular membrane(s) nationallicence 2,4-D : 2,4-dichloro-phenoxyacetic acid nationallicence LAB : lactic acid buffer nationallicence MX : polymer matrix membranes nationallicence UDOS : unilateral desorption from the outer surface nationallicence Baur Peter Institut für Obstbau und Baumschule, Universität Hannover, Am Steinberg 3, D-31157, Sarstedt, Germany aut Marzouk Hend Institut für Obstbau und Baumschule, Universität Hannover, Am Steinberg 3, D-31157, Sarstedt, Germany aut Schönherr Jörg Institut für Obstbau und Baumschule, Universität Hannover, Am Steinberg 3, D-31157, Sarstedt, Germany aut Bauer Hubert Institut für Obstbau und Baumschule, Universität Hannover, Am Steinberg 3, D-31157, Sarstedt, Germany aut Planta Springer-Verlag 199/3(1996-07-01), 404-412 0032-0935 199:3<404 1996 199 425 https://doi.org/10.1007/BF00195732 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00195732 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Baur Peter Institut für Obstbau und Baumschule, Universität Hannover, Am Steinberg 3, D-31157, Sarstedt, Germany aut NATIONALLICENCE 700 1- Marzouk Hend Institut für Obstbau und Baumschule, Universität Hannover, Am Steinberg 3, D-31157, Sarstedt, Germany aut NATIONALLICENCE 700 1- Schönherr Jörg Institut für Obstbau und Baumschule, Universität Hannover, Am Steinberg 3, D-31157, Sarstedt, Germany aut NATIONALLICENCE 700 1- Bauer Hubert Institut für Obstbau und Baumschule, Universität Hannover, Am Steinberg 3, D-31157, Sarstedt, Germany aut NATIONALLICENCE 773 0- Planta Springer-Verlag 199/3(1996-07-01), 404-412 0032-0935 199:3<404 1996 199 425 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer