Topochemical investigation on tension wood fibres of <i>Acer</i> spp., <i>Fagus sylvatica</i> L. and <i>Quercus robur</i> L.

Abstract

Abstract Topochemical detection of lignin and phenolic compounds was carried out at subcellular level in tension wood fibres of maple ( Acer spp.), beech ( Fagus sylvatica ) and oak ( Quercus robur ) by means of cellular UV-microspectrophotometry (UMSP) and confocal Raman microscopy. UMSP field scans at 278 nm revealed the presence of aromatic compounds in the gelatinous layer (G-layer) in tension wood of all three species. Characterisation of the detected substances by point measurements from 240 nm to 400 nm revealed a plausible relationship to by-products from the lignin biosynthesis pathway. Raman spectra, recorded from different regions within the G-layer, showed a high affinity to spectra of lignins. The degree of aromatic compounds in the G-layer of oak tension wood fibres was approximately three-fold higher than that in maple and beech. Moreover, the oak G-layer showed an accumulation of aromatic compounds towards the cell lumen up to 50% higher than that detected in the secondary cell wall. UMSP and Raman microscopy are considered valuable complementary methods for topochemical investigation on a subcellular level.