Peroxidase activity was determined by the protocol of
Hammerschmidt, Nuchles, and Kuc (1982). The enzyme reaction
mixture containing 1 ml of 0.1 M potassium phosphate buffer
(pH 6.8), 0.5 ml of 50 mM guaiacol and 0.5 ml of 0.2 mM hydrogen
peroxide was prepared. This mixture was used as a blank reading
at 470 nm. Then 1 ml of this reaction mixture was placed in
1.5 ml plastic cuvettes and 0.5 ml of the diluted enzyme extract
(crude protein extract) was added. Peroxidase activity was measured
by monitoring the increase in absorbance at 470 nm for
60 s. One unit of enzyme activity was defined as increase in one
OD value at A470 nm/min.