Phase behaviour and crystallinity of plant cuticular waxes studied by Fourier transform infrared spectroscopy

Abstract

The phase behaviour of cuticular waxes from leaves of Hedera helix L. and Juglans regia L. was studied by Fourier transform infrared spectroscopy. For this purpose reconstituted waxes, isolated cuticular membranes, dewaxed polymer matrix membranes and whole leaves were studied in the horizontal attenuated total re¯ection and transmission modes. Melting curves of cuticular waxes were derived from temperature-dependent changes in the absorption maximum of the symmetric stretching mode of CH 2 groups (m s , at approx. 2856± 2848 cm A1 ). With increasing temperature absorption band doublets due to CH 2 scissoring (d sciss ) and rocking (d rock ) movements (at approx. 1473±1471 and 730±720 cm A1 , respectively) indicative of an orthorhombic arrangement of alkyl chains merged into a single peak. The area ratio of the peaks at approx. 720 and 730 cm A1 was used as a measure for aliphatic crystallinity of plant cuticular waxes at a given temperature. The investigations of reconstituted cuticular waxes and those still embedded in isolated cuticles or in situ on the leaf produced comparable results. The ®ndings are discussed in terms of the properties of the cuticular transport barrier.Abbreviations: CM = cuticular membrane; FTIR = Fourier transform infrared; h-ATR = horizontal attenuated total re¯ection; IR = infra-red; MX = polymer matrix membrane Correspondence to: M. Riederer;

Fermented beverages of pre- and proto-historic China

“…This result is consistent with the 730-720 cm Ϫ1 infrared absorption band caused by straight-chain hydrocarbons (25), accentuated in the chloroform extracts. Contamination from petroleum contaminants, possibly derived from groundwater percolation of pesticides or herbicides or laboratory-introduced, was ruled out by running blanks and because the boiling ranges of n-alkanes in modern products have different ranges of n-alkanes than those observed for the ancient series.…”

Fuel pellets from biomass: The importance of the pelletizing pressure and its dependency on the processing conditions

“…FTIR-ATR spectra also show evidence of wax/oils migrating to the surface at higher temperatures which will be discussed later. , which are related to C-H stretches, have earlier been linked to hydrophobic extractives such as waxes and oils [34]. There are only minor differences in the spectra of straw pellets produced at 20 and 100 °C, which can be explained by the fact that straw naturally is coated by a cuticula, rich in low molecular weight waxes.…”

A study of bonding and failure mechanisms in fuel pellets from different biomass resources

“…wax), and one can clearly see two peaks, that are the relatively narrow CH (C-H bonds within a methyl group) stretching bands at 2850 and 2920 cm -1 [31] caused by wax. The main distinguishing features of the straw (4) versus wood samples (2) and (3) in Figure 7, are the two wax layer CH stretching bands [31], which are not observed for the wood samples. Furthermore, the straw fracture surface has a relatively small surface layer concentration of lignin, which is deduced from the weakness of the lignin 1510 cm -1 band [32,33] relative to the strong1030 cm -1 band, which is dominated by the cellulose component.…”

“…Figure 7 (1) shows the spectra of the extractive from straw (i.e. wax), and one can clearly see two peaks, that are the relatively narrow CH (C-H bonds within a methyl group) stretching bands at 2850 and 2920 cm -1 [31] caused by wax. The main distinguishing features of the straw (4) versus wood samples (2) and (3) in Figure 7, are the two wax layer CH stretching bands [31], which are not observed for the wood samples.…”