The activity of guaiacol peroxidase (GPOD) was assayed following the method described by Cakmak and Marschner [32] with some modifications. The reaction mixture contained 25 mM phosphate buffer (pH 7.0), 0.05% guaiacol, 10 mM H2O2, and the enzyme.
The activity was determined based on the increase in absorbance at 470 nm caused by guaiacol oxidation (E = 26.6 mM cm−1).