The relationship of extractives-free (EF) lignin content, lignin monomeric composition as syringyl/guaiacyl (S/G) ratio by thioacidolysis, and neutral sugars constituting hemicellulose by hydrolysis with trifluoroacetic acid was examined. This was performed in the same trunk by their within-tree variations, which mean the investigation with the same genes, in Eucalyptus camaldulensis and E. globulus. As results, each species had a high negative correlation between EF-lignin content and lignin S/G ratio although the difference between species and/or individuals was observed in the trend of within-tree variations of the wood properties. The relationship between EF-lignin content and lignin S/G ratio is considered to be caused from the difference in the fiber morphology from the relationship between lignin and EF-basic density which may relate to the fiber morphology. Furthermore, the relationship between the lignin monomeric composition derived from b-O-4 bonds and the hemicellulose composition is concluded to exist since common trend was observed between two species as higher lignin S/G ratio with the increase in xylan and or with decrease in arabinogalactan (galactan). We also discuss and suggest that the hemicellulose composition can influence on the lignin monomeric composition.
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