Combined Effects of Excess Mn and Low pH on Oxidative Stress and Antioxidant Enzymes in Cucumber Roots

The effects of excess Mn on oxidative stress and antioxidant enzymes in cucumber roots under different pH (pH 4.5 and 6.5) were studied. The results indicated that lipid peroxidation was increasingly serious with the increased concentration of Mn, especially under low pH. As a result, the growth of cucumber roots and shoots was significantly inhibited. Excess Mn led to an elevation in activities of Mn-SOD and Fe-SOD, which played an important role in removing . CAT was sensitive to excess Mn, and its activity significantly decreased under excess Mn and low pH, while activities of GPX, APX, DHAR and GR increased under low pH and to some extent under excess Mn, which indicated their important roles in scavenging reactive oxygen in tolerance to low pH and excess Mn of cucumber roots.