Chemical Characterisation of Compression Wood in Plantation Grown Pinus Radiata
Nanayakkara, B. (2007). Chemical Characterisation of Compression Wood in Plantation Grown Pinus Radiata (Thesis). The University of Waikato, Hamilton, New Zealand. Retrieved from http://hdl.handle.net/10289/2343
Permanent Research Commons link: http://hdl.handle.net/10289/2343
The primary objective of this study was to find out if changes in chemistry could beused to quantify Pinus radiata compression wood severity or degree of compressionwood development. Basic chemical composition and the lignin structure was assessedfor a range of different compression wood samples sourced from juvenile wood,mature wood, earlywood, latewood, branches, knots, 2-year and 1-year old Pinusradiata. Fluorescence microscopy was used as the reference method to assess thedegree of compression wood development. Lignin structure of compression wood wasstudied by thioacidolysis, size exclusion chromatography, and thioacidolysis/31P NMRspectroscopy.Variation in the basic chemical composition and lignin structure with compressionwood severity was ascertained. Results showed that, as the severity of compressionwood changed, progressively from normal through mild to severe, all chemicalparameters commonly associated with compression wood changed concurrently. Withincreasing severity lignin and galactose levels increased while glucose and mannoselevels decreased.Lignin structural changes were also associated with changing severity of compressionwood. Levels of p-hydroxyphenyl (H) releasable β-ethers increased and guaiacyl (G)releasable β-ethers decreased. Similarly, levels of uncondensed p-hydroxyphenyl units increased, while uncondensed guaiacyl units decreased. Similar proportions ofcondensed guaiacyl units were present in compression wood and normal wood.Similar trends in chemical composition were observed between the compression woodand related opposite wood in branches, knots and young wood of Pinus radiata.A number of chemical parameters changed linearly with compression wood severity.They were: the amount of lignin and galactose, the galactose/glucose ratio andp-hydroxyphenyl content in lignin. Parameters based on the p-hydroxyphenyl unitcontent in lignin, the H/G releasable β-ether ratio, releasable p-hydroxyphenyl β-etherunits and uncondensed p-hydroxyphenyl C9 units are most suitable indicators ofcompression wood severity as they spanned a larger range relative to the normal woodlevels and were not influenced by the morphological origin of wood samples.Chemical methods for quantifying compression wood severity should focus on thedetection and measurement of these parameters.Galactan present in Pinus radiata compression wood was isolated and characterised.Structural investigation by methylation analysis and NMR spectroscopy revealed thatthis galactan was largely composed of (1→4)-linked β-D-galactopyranose residues. Noevidence was found to indicate the presence of any branches.Characterisation of lignin in cell wall fractions of Pinus radiata normal wood revealedthat middle lamella lignin has a higher lignin content, a lower amount of releasableβ-ethers and a more condensed lignin than the secondary wall lignin. Levels ofreleasable p-hydroxyphenyl units were not higher in middle lamella lignin.A new method based on thioacidolysis and 31P quantitative NMR spectroscopy forestimation of the degree of lignin condensation of the phenolic and etherified C9 unitsin in situ wood lignin is described. Using this method it was found that phenolic C9units in in situ lignin were considerably less condensed than etherified C9 units in bothcompression wood and normal wood.
The University of Waikato
All items in Research Commons are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.
- Masters Degree Theses