The behavior of deuterium-labeled monolignol and monolignol glucosides in lignin biosynthesis in angiosperms

To examine the behavior of monolignol and monolignol glucosides in lignin biosynthesis, pentadeutero[9-D(2), 3-OCD(3)]coniferyl alcohol and pentadeutero[9-D(2), 3-OCD(3)]coniferin were synthesized and fed to growing Eucalyptus camaldulensis and Magnolia kobus. The differences in the incorporation patterns of these labeled precursors were studied using gas chromatography-mass spectrometry (GC-MS). Both precursors were incorporated into lignin, but the labeled coniferyl alcohol was incorporated more directly, resulting in a high proportion of pentadeutero-labeled guaiacyl and syringyl units in newly formed xylem, while labeled coniferin tended to be incorporated in lignin as tetradeutero units, especially in syringyl lignin in both trees. However, the incorporation efficiencies of the precursors into syringyl lignin were higher in Magnolia than in Eucalyptus, and the ratios of tetradeutero to pentadeutero in guaiacyl lignin were lower in Magnolia than in Eucalyptus when the trees were fed coniferin.