Characterisation of lignin from CAD and OMT deficient Bm mutants of maize
1997
Provan, G.J. | Scobbie, L. | Chesson, A.
Internodes of the maize cell line W401 and bm1 and bm3 mutants expressed in W401 were harvested 5 days after anthesis (A5) and at silage (S) stage. The normal maize had a higher total phenolic (TP) content (80.5-90.5 g kg-1 cell wall DM) than both bm1 and bm3 mutants (74.4-86.4 and 66.0-84.2 g kg-1 cell wall DM, respectively). TP were inversely related to cellulase digestibility with values of 85.4-91.5, 89.3-92.1 and 91.3-94.1% for normal, bm1 and bm3. Marked differences in p-coumaric acid concentrations were found ranging from 20.9 to 26.3 g kg-1 cell wall DM for normal, 14.9 to 15.3 g kg-1 for bm1 to 10.1 to 14.4 g kg-1 for bm3. The ferulate pattern was entirely different with the bm1 genotype providing the lowest total (9.1-10.7 g kg-1) and etherified (1.9-2.3 g kg-1) values. Although the bm3 contained more total ferulate (11.5-13.1 vs 10.9-11.7 g kg-1), the normal variety had a significantly greater amount of etherified ferulate (2.8-3.4 vs 3.2-4.1 g kg-1) implying a greater extent of cross-linking between wall polymers. Recovery of guaiacyl and syringyl residues was greatest in the normal maize with the bm1 occupying the middle position between the two extremes. Calculated S:G ratios from 4 M NaOH digestion and NMR were in good agreement with the normal line giving the highest ratio, bm1 intermediate and bm3 the lowest. Colorimetric analysis revealed a large increase in the aldehyde content of the in situ bm1 lignin compared to normal and bm3 genotypes although NMR failed to reveal significant numbers of aldehydic resonances.
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