The effect of different concentrations of pyrene on photosynthetic pigment content and antioxidant enzymes activity in sunflower (Helianthus annuus)

World industrialization and population growth are the main reasons for the increase in environmental contamination with aromatic hydrocarbons. The presence of these compounds in the environment leads to a variety of stresses in plants and finally reduces their growth. Pyrene is one of the major toxic contaminants belonging to polycyclic aromatic hydrocarbons. Hence, in this research, the effect of 50 and 100 ppm of pyrene on growth indices, photosynthetic pigment contents, the activity of some antioxidant enzymes, malondialdehyde content, and amount of hydrogen peroxide in sunflower have been examined. Pyrene significantly reduced chlorophyll amount, anthocyanin content, catalase activity, and hydrogen peroxide content compared to the control, while the amount of plant carotenoids, the activity of superoxide dismutase  and peroxidase enzymes as well as malondialdehyde content were increased in the roots and shoots of sunflower. Based on the obtained results, pyrene probably caused an oxidative stress and lipid peroxidation that eventually reduced photosynthetic pigments and plant growth.