Ecotoxic responses of CytP450 and antioxidant enzymes in maize due to exposures to Phenanthrene and Pyrene in soil

Maize (Zea mays L.) was chosen to study the ecotoxic-responses of cytochrome P450 and antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) upon exposure to two Polycyclic Aromatic Hydrocarbons (PAH's), phenanthrene (PHE) and pyrene (PY), in brown meadow soil. Results indicated that phenanthrene and pyrene exposure caused a stress response and therefore changes in the antioxidant recovery and metabolic detoxification systems in plants. CytP450 content had a positive correlation with the low concentrations of PHE and PY individually (r = 0.834, p < 0.01), and a negative correlation with a mixture of PHE and PY at the same concentration, indicating that the combination of PHE and PY resulted in a synergistic ecotoxic effect and decreased the plant's metabolic detoxification ability. PHE and PY both had a negative correlation to SOD activities and a positive correlation to CAT activities in individual exposures. POD activities were influenced by the water solubility of PHE, but affected by the total concentration of PY. SOD, CAT and POD all showed a positive correlation when exposed to PHE and PY combined, which illustrated an antagonistic effect and resulted in lowered ability to prevent oxidant damage. Our study can form the basis of ecological evaluation of PAHs exposure in soil, providing early diagnosis of ecotoxicity.