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Growth and antioxidant system responses of maize (Zea mays L.) seedling to different concentration of pyrene in a controlled environment

Polycyclic aromatic hydrocarbons (PAHs) are a class of organic pollutants effecting different aspects of plants physiology. To assess the physiological responses of plants to PAHs, maize (Zea mays) was treated with 25, 50, 75, and 100 ppm of pyrene and after 21 days, the activity of some antioxidant enzymes, malondialdehyde (MDA), total flavonoid, total anthocyanin, and soluble sugar contents were measured in shoots and roots of plants. Pyrene led to increase MDA content as well as CAT, POD, and SOD activities. Increase in pyrene concentration reduced all studied growth variables and significantly increased photosynthetic pigments contents of plants. Soluble sugar content was significantly higher in the shoot, while that was reduced in the roots through increasing of pyrene concentration (p < 0.05). Also, the increase of pyrene concentration decreased total flavonoid content compared to anthocyanin content. In conclusion, these findings supported the hypothesis that pyrene toxicity induces oxidative stress in the maize plant and it also increases the antioxidant systems in order to moderating stress condition. However, the antioxidant system of maize was not strong enough to eliminate all produced ROS at high concentrations, thus this caused oxidative damage to the plant and decreased its growth variables.