Study of phenanthrene and pyrene effects on photosynthetic pigments, membrane stability and antioxidant enzymes activities in wheat (Triticum aestivum L.)

Polycyclic aromatic hydrocarbons (PAHs) are an important group of pollutants which are released into the environment mainly due to incomplete combustion of organic materials. PAHs frequently detected at relatively high concentrations in soils of some regions and are toxic for organisms including plants. In this study, wheat plants were grown hydroponically and treated by different concentrations of phenanthrene and pyrene. After determination of effective levels of two compounds, their effects on some physiological and biochemical parameters were evaluated. While pyrene showed no significant effect on studied parameters, phenanthrene significantly decreased photosynthetic pigments content and membrane stability index of shoot and root. Also, phenanthrene significantly increased malondialdehyde content of shoot and root; and hydrogen peroxidase content of root but decreased hydrogen peroxidase of shoot. Phenanthrene significantly decreased CAT, POD, SOD and APX activity in shoot, while pyrene only decreased APX activity. Both compounds decreased CAT, POD, SOD and APX activity in root, but the effect of phenanthrene was higher than that of pyrene. According to the results of this study, phenanthrene inhibited antioxidant enzymes activities and caused oxidative stress more than that of pyrene, and therefore led to higher reduction in photosynthetic pigments, plasma membrane integrity and ultimately plant growth.