Peroxidase activity in citrus tissues

Peroxidase activity has been determined in various citrus tissues and varieties using four H-donors : pyrogallol, guaiacol, p-methylaminophenol-sulphate (metol) and p-phenylenediamine (PPDA). Results showed that fruits, leaves and roots, respectively, have increasing peroxidase activity, regardless of the H-donor used, indicating that the characteristics of the tissue used have a more pronounced effect on activity than the type of the H-donor. The relationship between H₂O₂ and H-donors which serve as substrate for the peroxidase was examined thoroughly. A wide range of combinations of H₂O₂ and different H-donors in various concentrations was tested in. order to define the optimal conditions for each tissue. As for peroxidase from other sources, it was found that in all citrus tissues and varieties tested there exists an interdependence between both substrates.