| Abstract
| - Most studies published thus far on the four brown midrib (bm) mutants (bm1, bm2, bm3, and bm4)in maize (Zea mays L.) have focused on one or two individual mutants, and comparisons betweenstudies have been difficult because of variation in genetic backgrounds, maturity, and source of tissue.Detailed analyses of the stalks of the four bm single mutants and a bm1−bm2 double mutant in acommon genetic background (inbred A619) revealed structural and compositional changes in theirisolated cell walls and lignins compared to the wild-type inbred. 2D-NMR revealed a significantpresence of benzodioxane units in the bm3 isolated lignin. 1D 13C NMR revealed increased aldehydelevels in the bm1 and bm1−bm2 mutants compared to the wild-type inbred. The bm3 and bm1−bm2mutants contained less Klason lignin in the isolated cell walls. The bm1, bm3, and bm1−bm2 mutantscontained ∼50% less esterified p-coumaric acid with noticeably elevated levels of ferulate in thebm3 mutant. A difference among bm mutants in the solubility of p-coumaric acid−lignin complexesduring cellulase enzyme treatment was also discovered, suggesting that the bm mutations mightalso differ in the structural organization of lignin. Keywords: Maize; Zea mays L.; brown-midrib mutants (bm1, bm2, bm3, bm4); lignin; cell wall; NMR;benzodioxane
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