Abstract:The alleviating effects of iron (Fe) supplementation on zinc (Zn) toxicity were investigated in hydroponic Solanum nigrumseedlings. Hydroponic method was used to raise S. nigrumseedlings with three combined Zn and Fe concentrations - of 400 μmol·L ^-1Zn, 0 μmol·L ^-1Fe, 400 μmol·L ^-1Zn + 200 μmol·L ^-1Fe and standard 0.5 Hoagland nutrient solution as the control. The results showed that seedling height, root length and chlorophyll content reduced while H ₂O ₂accumulation significantly increased in Zn-treated S. nigrumseedlings. Supplementation with Fe did not only improve Zn tolerance, but also increased gene expression and enzyme activities of SOD, CAT and APX in S. nigrumseedlings. RT-PCR results showed that supplementary Fe significantly increased FeSOD2and CAT1genes expressions. These results indicated that Zn toxicity-induced oxidation damage and growth inhibition were largely due to Zn-induced Fe deficiency in plants. Supplemental Fe in Zn-poisoned conditions improved FeSOD2and CAT1genes expressions. This enhanced antioxidant enzyme activity and reduced reactive oxygen species (ROS) level and oxidative damage of plants. The study provided the theoretical basis for further studies on molecular mechanisms of plant response to Zn toxicity and the practical applications for phytoremediation technology.