Growth and Activities of Antioxidant Enzymes in Wheat Seedlings under Combination Stress of Simulated Acid Rain,Aluminum,Cadmium and Lead

Effect of single and combined stress of aluminum(3,30 mg·L-1),cadmium(0.1,1 mg·L-1) and lead(25,250 mg·L-1) under acidic rain on growth and activities of antioxidant enzyme were studied in wheat seedlings.The experimental results showed that Al,Pb and Cd can inhibit root length,shoot height and root number per seedling significantly after exposure to single or combined metal ions for 6 days or 12 days.The decrement of root length and shoot height were 54.01%～94.81% and 18.88%～77.95% respectively,while root number per seedling decreased by 21.87%～80.37% after exposure for 12 days.The inhibition effects increased with increasing treatment concentrations and prolonged exposure duration,meanwhile stronger inhibition effects were found in the combination treatments of three metal ions and simulated acid rain.The activities of SOD increased significantly after seedlings exposed to single metal ion Al,Pb or Cd and simulated acid rain,but decreased markedly after exposure to the combination of three metal ions and simulated acid rain.POD activity increased significantly in all treatment groups,however CAT activity decreased at the same time.The results showed that the combination of simulated acid rain and metal ion caused oxidative stress in plants,and higher toxicity occurred after seedlings exposed to the combination of simulated acid rain and three metal ions.