An NMR microscopy study of water absorption in cork

NMR Microscopy is used to measure the imbibition of water into natural cork , extractives-free cork and desuberised cork. The results clearly indicate that suberin is the key constituent which determines the ability of cork to resist water uptake. Furthermore, a particular suberin with distinct spect ral properties as viewed by C-13 NMR is shown to be the component responsib le for cork resistance to water absorption. Laser confocal microscopy sugge sts that this function is associated with the role of suberin in preserving cell wall structure but the highly hydrophobic nature of suberin may also play an important role. The NMR microscopy study shows that the water absor bed by natural cork, after soaking for three days, is confined to the lenti cels, narrow channels on the order of 1000 to 1500 mu m in diameter. One in cidental outcome is the observation of a clear down-field shift in NMR freq uency for water near the cut transverse surfaces of the cork, an effect ass ociated with susceptibility inhomogeneity. (C) 2000 Kluwer Academic Publish ers.