Fig. 7.

Effect of combining different phenols with p-coumaric acid as the control phenol on the induction capability for NADH-peroxidase activity of four POD isoenzymes. POD isoenzymes were eluted from BN gels (see Fig. 3 and Materials and methods). Measuring solution (0.1 M succinate buffer, pH 5.5) consisted of 0.166 mM p-coumaric acid, 16 mM MnCl₂, 0.22 mM NADH, and 0.0166 mM of one of the following phenols to examine interactions between phenols: benzoic acid, ferulic acid, caffeic acid, chlorogenic acid, gallic acid, protocatechuic acid, syringic acid, or vanillic acid. Activities are expressed as relative values in relation to activities when p-coumaric acid was applied alone (in the same concentration). For the calculation of enzyme activities, extinction coefficients were adapted (see Supplementary Table S1 at JXB online). Results are from two independent experiments including plant growth and protein separation.