Raman-spectroscopy-based noninvasive microanalysis of native lignin structure.

A new robust, noninvasive, Raman microspectroscopic method is introduced to analyze the structure of native lignin. Lignin spectra of poplar, Arabidopsis, and Miscanthus were recovered and structural differences were unambiguously detected. Compositional analysis of 4-coumarate-CoA ligase suppressed transgenic poplar showed that the syringyl-to-guaiacyl ratio decreased by 35% upon the mutation. A cell-specific compositional analysis of basal stems of Arabidopsis showed similar distributions of S and G monolignols in xylary fiber cells and interfascicular cells.