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Activity of peroxidase, superoxide dismutase and catalase were examined in leaves, stems and roots of olivacea (oli) and monstrosa (mon) mutants of Lycopersicon esculentum Mill. The extent of the difference between the pattern of oxidative enzyme activities of the wild type (Wt) and the mutants was determined. The high peroxidase activity during the developmental stages of the leaves and stems of oli and mon phenotypes is associated with high levels of 4 anodic peroxidases in leaves and of two isozymes in the stem. Leaves of oli exhibit higher activity of the cathodic peroxidase C2, while both mutations have a marked increase of peroxidase C1 in stems. A positive relation between high peroxidase activity and oxidative stress damage was found: in chilling experiments at 5°C, peroxidase level in mutants and wt leaves was negatively correlated with electrolyte leakage. Superoxide dismutase (SOD) activity rises in oli stems around flowering time due to the high activity of the chloroplast forms SOD-1 and SOD-2. Catalases (CAT) were detectable only in early stages of plant development; CAT-2 was nearly absent in wild type tissues but well represented in mon and oli. The oli and mon mutations may affect critical steps of a regulatory pathway controlling various classes of oxidative enzymes in tomato. [ABSTRACT FROM AUTHOR]