Fig. 3. Relative polyphenol oxidase activity of seeds obtained from four wheat cultivars using the six different substrates indicated. The ordinate shows the change in absorbance at 410 nm (phenol and catechol) or 475 nm [L-tyrosine, methyl catechol, 3,4 dihydroxyphenylalanine (L-DOPA), and caffeic acid]. Catechol, methyl catechol, L-DOPA and caffeic acid reactions were conducted at 10 mM substrate in 50 mM 3-(N-morpholino) propane sulfonic acid (MOPS) (pH 6.5); phenol at 2 g L-1 and 50 mM MOPS (pH 6.5); and tyrosine at 10 mM in 50 mM Tris (pH 8.5). Absorbance readings are the average of nine replicate standard assays per cultivar (three seeds per assay). Error bars represent one SD above the mean.
