Comparison of leaf and stem cell-wall components in barley straw by solid-state 13C NMR

Abstract Barley straw was separated mechanically into leaf and stem fractions. Their 13 C NMR spectra were recorded at low field (25 MHz) using magic-angle spinning and cross-polarisation (CP-MAS) under conditions optimised for quantitation of lignin. The stem fraction contained more lignin with a higher proportion of ether-linked syringyl residues. The leaf fraction contained more phenolic acids and cutin. The molecular rigidity of the components of the stem cell walls was estimated from the 13 C spin-lattice relaxation time T 1 , which decreases with thermal motion. Crystal-interior cellulose and syringyl lignin were the most rigid polymeric components. These data have implications for the capacity of the straw to withstand mechanical stress and to resist degradation during digestion by ruminants.

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