Physiological Response To Copper Stress In Wheat Supplied With Varying Nitrogen

Adverse conditions have a big impact on the agricultural production,which was seriously affected by heavy metal pollution.In this study,the wheat cultivar,Chuanmai 104,was used as material to investigate the effect of nitrogen nutrition on wheat growth,photosynthesis and antioxidant capacity under copper stress and reveal the physiological and biochemical mechanism of resisting and acclimating heavy metal pollution in wheat.These results will provide the scientific basis for rational fertilization in angricultural production.The main results are as follows:(1)Cu stress significantly decreased plant dry mass,root length,paint height root surface area,pigment content,net photosynthetic rate,intercellular CO2 concentration,stomatal conductance and transpiration rate,limited the absorption and utilization of nitrogen nutrition and mineral nutrients(Fe,Mn,Zn,Ca,Mg),inhibited the activity of antioxidant enzymes(SOD,APX,GPX,CAT,GR)and decreased the soluble protein content in wheat,but increased the contents of malondialdehyde(MDA),proline(Pro)and soluble sugar under Cu stress.It also significantly increased the content of Cu in shoots and roots of wheat.These results indicate that Cu stress inhibited the activity of antioxidant enzymes and the photosynthetic parameters,decreased the the absorption and utilization of mineral nutrients.(2)Low and medium concentration of ammonium nitrogen treatment significantly improved the resistance and adaptability of wheat to copper stress.Compared with nitrate nitrogen treatment,ammonium nitrogen significantly decreased the content of MDA and Pro in wheat seedling,increased the pigment content,enhanced the absorption of mineral nutrients,and increased the biomass of wheat seedling.In addition,ammonium nitrogen treatment significantly increased the activity of SOD,APX,GPX,CAT and NR and increased the content of soluble protein,whereas decreased the Cu content in shoots and roots of wheat.Therefore,low and medium concentration of ammonium treatment can mitigate the toxicity of Cu by improving the photosynthetic parameters,increasing antioxidant enzymes activity and enhancing nutrients absoption and utilization.(3)Under Cu stress,significant differences in growth and development of wheat were observed under high concentration of different nitrogen form treatment.Compared with nitrate treatment,ammonium treatment significantly decreased the biomass,palnt height,pigment content,net photosynthetic rate,intercellular CO2 concentration,stomatal conductance and transpiration rate in wheat seedlings under Cu stress.At the same time,it also decreased the activity of SOD,APX,GPX,CAT and NR,increased the content of MDA and accumulated more Cu content in wheat seedlings.The reason could be that ammonium toxicity aggravated stress effect from Cu and inhibited the growth and development in wheat.