SPECTROPHOTOMETRIC INVESTIGATIONS ON LIGNIN IN WHEAT (TRITICUM-AESTIVUM L) - INFLUENCE OF CELL-WALL PREPARATION, SOLVENT AND STANDARD

Absorbance at 280 nm was used to determine lignin concentrations in so lutions of cell walls from winter wheat whole-crop silage, stems, and straw. Three different cell wall preparations (hot water-organic solve nt fiber, ethanol-benzene residue, neutral detergent fiber) were prepa red and dissolved in either HCl-triethylene glycol or acetyl bromide. Three phenolic standard solutions were used to calculate lignin concen trations in the wheat materials from absorbance readings: mixtures of phenolic monomers based on aldehydes (HIGUCHI), aldehydes and acids (R EEVES), and washed Indulin (WIND). Gravimetric Klason lignin determina tion on the cell wall preparations consistently gave higher values tha n spectrophotometric lignin analysis. Material recovered as cell wall was slightly greater for hot water-organic solvent fiber than for neut ral detergent fiber and was lowest for ethanol-benzene residue, probab ly due to partial dissolution of cell wall components with the latter procedure. Acetyl bromide shifted UV spectra about 10 nm to lower wave lengths, which complicates quantification of absorbance readings. Addi tionally, triethylene glycol is easier to handle and less toxic. Ligni n concentrations related to the REEVES standard were more consistent a cross cell wall preparations and solvents than other standards. It app ears that the REEVES standard was best suited for winter wheat whole-c rop silage, stems, and straw.