The constituents of the soluble cuticular lipids (SCL) of the leaf blades of Citrus aurantium L. were identified by gas chromatography-mass spectrometry and quantified. Major components were 1-alkanols (C24 to C40), n-alkyl esters (C36 to C56), n-alkanoic acids (C28 to C34), n-alkanes (C22 to C40) and triterpenones, while n-alkanals (C29 to C38), sterols, and alkyl benzenes (molecular weights 260, 274 and 288) made minor contributions. Leaf age and side significantly affected the quantitative composition of SCL. Increased day temperature during the development of leaves led to decreased amounts per unit area of n-alkanes, 1-alkanols, n-alkanoic acids and n-alkyl esters while increased night temperatures resulted in increased amounts of n-alkanes n-alkanoic acids and 1-alkanols. Relative humidity had no effect on the amounts or composition of SCL. The permeability of cuticular membranes to water (described in part I of this paper) and the composition of SCL were not related. A model for the molecular structure of the transport-limiting barrier of plant cuticles and for the transport of water across it is proposed.
Dillusion I Fluidchromatographie I Gase I Hohe Driicke I LaminarstromungBinary diffusion coefficients D , , have been determined for benzene, n-propylbenzene and 1,3,5-trimethylbenzene in supercritical CO, at 40°C from 80 to 160 bar and additionally between 35 and 55°C at 110 and 130 bar with the chromatographic broadening technique (CBT). The effect of secondary Now was investigated. The observed binary diffusion coefficients are of the order of 2 .cmz . s-I . For a pressure rise from 80 to 160 bar, the diffusion coefficients decrease by about 50%. The isobaric temperature dependence of diffusion coefficients at 110 bar is substantially higher than that at 130 bar; for constant densities p. however, the temperature coefficients seem to be very small. n-Propylbenzene was found to diffuse faster than its structural isomer 1,3,5-trimethylbenzene. At higher densities F = ( D 1 2 . p)/(D,, .p)id rises well above the value given by the Enskog-Thorne theory and finally approaches approximately unity.Die binaren Diffusionskoeffizienten D,, von Benzol, n-Propylbenzol und 1,3,5-TrimethylbenzoI wurden bei 40°C von 80 bis 160 bar sowie bei 110 und 130 bar von 35 bis 55°C nach der chromatographischen Peakverbreiterungsmethode experimentell bestimmt. Der Effekt der Sekundarstromung wurde untersucht. Die beobachteten Diffusionskoeffizienten sind von der GroOenordnung 2 .cmz . s -' . Durch eine Druckerhohung von 80 auf 160 bar bei 40°C werden die Diffusionskoeffizienten um etwa 50% herabgesetzt. Bei 110 bar wurde eine hohere Temperaturabhangigkeit des binaren Diffusionskoeffizienten beobachtet als bei 130 bar; sie ist jedoch recht gering bei konstanter Dichte p. n-Propylbenzol diffundiert unter vergleichbaren Bedingungen schneller als sein Strukturisomer 1,3,5-Trimethylbenzol. Die experimentell erhaltenen Werte fur die GroRe F = (Dlz . P ) / ( D ,~ p)id liegen hoher als die nach der Enskog-Thorne-Theorie berechneten; bei hohen Dichten erreicht der experimentelle F-Faktor ungefahr den Wert eins.
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