Effects of Paper Mill Wastewater on Seedling Growth and Antioxidant System of Reeds

Effects of different concentrations of wastewater (chemical oxygen demands of 300, 175 and 50 mg·L^-1) from a paper mill on seedling growth and antioxidant system in reeds were tested in experimental pools that simulated the wetland ecosystem. Root length, biomass and moisture content, but not shoot moisture content and plant height, significantly increased with increases in wastewater concentration. At 300 mg·L^-1, shoot biomass increased by 52.5% and ischolar_main biomass increased by 73.05% over the control. Malondialdehyde content, production rate of superoxide anions and hydrogen peroxide content all decreased with increasing concentration. At 300 mg·L^-1, malondialdehyde content, production rate of superoxide anions and hydrogen peroxide content were 0.34, 0.24 and 0.16 times, respectively, those of the control in leaves and were 0.25, 0.19 and 0.17 times, respectively, those of the control in ischolar_mains. Superoxide dismutase, peroxidase and catalase activities and ascorbic acid and glutathione contents in reeds significantly increased with increasing concentrations of wastewater. These results suggest that a concentration of 300 mg·L^-1 could improve the activities of antioxidant enzymes, inhibit the generation of reactive oxygen species and reduce the generation of malondialdehyde, thus effectively alleviating the damage caused by salinity in wetland soil.