Study On The Physiological And Ecological Base Of Exogenous Salicylic Acid And Calcium In Repairing Maize By Cadmium Stress

The nutrient solution culture experiment was carried out to examine the effects ofexogenous salicylic acid （SA） on growth, chlorophyll, nitrate nitrogen accumulation inmaize leaves and antioxidase activities in maize seedling exposed to cadmium （Cd）stress. The Cd stress dramatically reduced the seedling growth and leaf chlorophyllcontent, and increased the nitrate accumulation in leaves due to interfering with thenitrogen metabolism. At the same time, Cd stress disturbed the antioxidase activities inseedling root. Applying exogenous SA with concentration50-250μmol·L^-1, the heightof maize increased by9.4%,26.0%and13.5%, the biomass of maize increased by13.5%,27.0%and13.5%, respectively. The leaf chlorophyll contents increased81.3%,115.2%and45.9%. The50μmol·L^-1exogenous SA reduced the nitrate content of leaf30%, comparing with that under Cd stress. It showed the exogenous SA maintained thenitrogen metabolism to work well in maize leave. The application of exogenous SAcould reduce the peroxidase （POD） activity to0.026min·mg, and the activity of PODand superoxide dismutase （SOD） in maize root had no markedly difference with thatunder Cd stress condition. The lower POD and SOD reduced the damage of Cd stress onthe plasma membrane oxidation system. But the role degree of exogenous SAalleviating Cd stress was affected by SA application concentration; application lowerconcentration SA had markedly repairing effects, and the higher SA concentration couldinhibit chlorophyll synthesis and enzyme activities. After treatment with100-200mg·L^-1exogenous Ca, the height increased5.3cm and10.5cm, the biomass increased0.07kg and0.17kg, respectively.100-400mg·L^-1Ca increased chlorophyll23.8%,113.9%,63.5%(Cd10μmol·L^-1) and55.1%,194.0%,168.1%(Cd40μmol·L^-1),100 mg·L^-1Ca could reduce the nitrate content to minimum, could markedly alleviate nitratenitrogen accumulation. Through compressively consideration factors, the SAconcentration with good repairing results were50^-100μmol·L^-1and the Caconcentration with good repairing results were100-200mg·L^-1.At the basis of analysis of the exogenous application of SA and Ca alleviationmechanism and the experiment result, carried out to examine the effects of the differentsplit-root experiments with nutrient solution culture on maize plants. The results showedthat, plants treated with split-root experiment for20days, Treatment T1significantlyreducted height of the maize0.75times and biomass0.52times, compared with control.Treatment T3, half of the roots stressed Cd and other part exposed SA, reducted theheight to60.3cm and biomass to0.15kg,0.73and0.46times in comparison withcontrol, respectively. Treatment T2, the roots exposed to Cd and SA, was no significantdifference. The results showed that the advantage of no stress root could not relieve theCd toxicity to maize. It is concluded that half of the roots exposed to Cd could inhibitthe seedling growth, but the roots exposed to Cd and SA had markedly repairing effects.Through research and analysis of chlorophyll, SOD and POD, we could receive sameconclusion.