The activity of the ascorbate peroxidase (APX, EC 1.11.1.1) was measured using the molar extinction coefficient for ascorbate (2.8 mM/cm), considering that 1 mol of ascorbate is required for a reduction of 1 mol of hydrogen peroxide (H2O2). Results were expressed as lmol H2O2/min/mg1 P (Nakano & Asada, 1981).