ρ-Cymene Inhibits Growth and Induces Oxidative Stress in Rice Seedling Plants

rho-Cymene was one of the major components of volatiles released by croftonweed. The allelopthy of rho-cymene on the growth of upland rice seedlings was performed. Hydrogen peroxide generation, malondialdehyde (MDA) content, proline content, total ascorbate (ascorbate/dehydroascorbate), reduced/oxidized glutathione, and the levels of induction of antioxidant enzyme were studied in the seedlings of upland rice. rho-Cymene inhibited the growth of upland rice seedlings. Exposure of upland rice seedlings to rho-cymene increased levels of H2O2, MDA, and proline, indicating lipid peroxidation and induction of oxidative stress. Activities of the antioxidant enzymes superoxide dismutase, catalase, peroxidase, guaiacol peroxidase, ascorbate peroxidase, and glutathione reductase were significantly elevated during the treatment period (7-15 d) compared with enzymes in the upland rice seedlings unexposed to rho-cymene, thereby indicating the enhanced generation of reactive oxygen species (ROS) upon rho-cymene exposure. These results suggest that activation of the antioxidant system by rho-cymene led to the formation of ROS that resulted in cellular damage and decreased growth of upland rice seedlings.