Analysis of static bending-induced compression wood formation in juvenile Picea omorika (Pancic) Purkyne

Abstract

Young P. omorika trees subjected to static bending showed a severe compression wood response as characterized by fluorescence spectroscopy/microscopy, which decreased in severity with height correlated with a decrease in bending moment. This investigation is aimed at understanding the reaction wood response in a slow-growing conifer species under conditions of severe and long-term bending stress. Compression wood (CW) formation was studied in stems of juvenile P. omorika after trees were subjected to static bending by wiring at an angle of about 90 degrees, for 1 year. The applied static bending would correspond to the impact of winter snow loads or snow falls on juvenile conifers. Stem sections were collected during one growing season and examined by fluorescence microscopy, and fluorescence spectroscopy including deconvolution analysis. Trees exposed to bending produced large amounts of severe CW but very low amounts of opposite wood (OW) during the experimental season indicating a dramatic change in biomass distribution compared to control trees. Indicators of cell wall structure changes, such as fluorescence emission spectra, peak intensities, and shifts in the positions of the long-wavelength spectral components, decreased from the stem base to the top of the stem, in line with a calculated decrease in bending moment.