Effects of Cd Stress on Antioxidant Enzymes Activity of Sonchus asper L. Hill. and Zea mays L. in Intercropping System

Intercropping has shown the potential to phytoremediate heavy metal polluted soils. A pot experiments were carried out to explore the antioxidant responses of Sonchus asper L. Hill and Zea mays L. to Cd pollution under intercropping system. Four cadmium levels (0, 50, 100, 200 mg/kg) was designed to study the effects of Cd on the contents of soluble protein and MDA, activities of SOD, POD, CAT and T-AOC in leaves of S. asper and Z.mays. The result showed that: with 0 and 50 mg/kg soil Cd content, the content of soluble protein in S. asper and Z.mays decreased by 8.1%~34.1% under intercropping, and with 100 and 200 mg/kg soil Cd content, the content of soluble protein in S. asper and Z.mays significantly increased by 34%~69.1%. Compared with monoculture, MDA contents of Z.mays increased by 6.1%~ 64.6% and decreased by 9.7%~58.7% in S. asper under intercropping. Under both monoculture and intercropping systems, the SOD, POD, CAT, T-AOC activities of S. asper and Z.mays all increased with increasing Cd concentrations. But Cd addition at 200 mg/kg caused CAT activity decrease. Under the same Cd concentration treatment, SOD activity, POD activity (except 200 mg/kg) , CAT activity and T-AOC activity of Z.mays decreased by 15.1%~48.3%, 2.8%~ 24.7%, 5.2%~42.3% and 20.7%~31.9% in intercropping, compared with monoculture. Under intercropping, T-AOC activity of S. asper increased by 11.2%~26.4%. In general, intercropping could improve antioxidant enzymatic system in Z.mays and S. asper , thus alleviate Cd toxicity under Cd stresses. The enzymatic antioxidation capacity plays important role in Cd tolerance of plant.