Assessment of paraquat genotoxicity on barley (Hordeum vulgare L.) seedlings using molecular and biochemical parameters

The effects of exposure of barley seedlings to different concentration (10^?6 to 10^?3 mol/l) of paraquat on seed germination, root length, antioxidant enzyme activities and randomly amplified polymorphic DNA (RAPD) profiles were investigated. The results revealed that malondialdehyde content significantly increased by exposing paraquat in a concentration-dependent manner (p < 0.05). A significant increase in peroxidase and catalase activities in seedlings was observed with increased concentration of paraquat, and then decreased when the value reached 10^?3 mol/l, whereas the activities of superoxide dismutase gradually increased with increasing paraquat concentration. Germination and root elongation also decreased with the increase of paraquat concentration. On the other hand, alterations of DNA in barley seedlings were detected using RAPD technique. The changes occurring in RAPD profiles of seedlings following paraquat treatment included loss of bands found in DNA of control seedlings and appearance of new bands. The results of this study showed that paraquat induced DNA damage in a dose-dependent manner and the root cells of barley showed a defense against paraquat-induced oxidative stress by enhancing their antioxidant activities.