Appropriate nitrogen fertilizer strengthens growth and antioxidative ability of Festuca arundinacea under salt stress

Abstract: In order to fertilize properly for F. arundinacea cultivated in the soil salinity areas, an experiment was conducted to investigate the effect of NH4NO3 on growth and antioxidative ability of F. arundinaceawas under NaCl stress. F. arundinacea plants cultured with Hoagland nutrient solution (excluding nitrate nutration) in pots was treated with nine cross combinations of different NaCl concentrations at 0, 70, and 140 mmol/L, and three nitrate nitrogen levels at 0.01, 0.6, 1.2 g/L (the nine treatments were 0+0.01, 70+0.01, 140+0.01, 0+0.6,70+0.6, 140+0.6, 0+1.2, 70+1.2, 140+1.2) for 25 days, and then the fresh weight, dry weight, water content, root dehydrogenase activity, nitrate reductase activity, NO3- content, membrane permeability, and MDA content were determined, and SOD, CAT isoenzyme activity and protein expression were also studied by polyacrylamide gel electrophoresis (PAGE) or SDS-PAGE. The results show that, compared with the same level of NH4NO3, the fresh weight, dry weight, and water content of F. arundinacea under salt stress were lower than those of F. arundinacea without salt stress, while the changes of root dehydrogenase activity, nitrate reductase activity, NO3- content, membrane permeability, and MDA content were in the opposite. PAGE or SDS-PAGE showed that SOD isoenzyme activities increase as CAT isoenzyme activities or protein expression changed. Under NaCl stress of the same concentration, when NH4NO3 concentration increased, the fresh weight, dry weight, water content, and SOD isozymes activity also showed an ascendant trend, but NO3- content, membrane permeability, and MDA content decreased. Compared with NH4NO3 level 0.01 g/L, NH4NO3 0.6 g/L made root dehydrogenase activity, nitrate reductase activity, CAT isoenzyme activity, and protein expression amount increase markedly; and compared with NH4NO3 level 0.6 g/L, NH4NO3 1.2 g/L not only made the increment rate depression of root dehydrogenase activity, nitrate reductase activity, but also made CAT isoenzyme activity and protein expression amount have little change. Therefore, under the same concentration of NaCl stress, compared with NH4NO3 0.01 g/L leavel, NH4NO3 0.6 g/L treatment strengthened the absorption ability on water and inorganic ion of root and the ability of reduction NO3-, and so improved the nitrogen nutrition of F. arundinacea. NH4NO3 0.6 g/L treatment also raised the ability of antioxidation, especially it markedly raised the ability of scanvaging H2O2, and so reduced membrane lipid peroxidation and endocyte exosmosis. Moreover, NH4NO3 0.6 g/L treatment intensified the protein expression amount. All the changes contributed to the improved ability of the salt resistance of F. arundinacea. Under the same concentration of NaCl stress, compared with NH4NO3 0.6 g/L level, NH4NO3 1.2 g/L raised the ability of reduction NO3-; NH4NO3 1.2 g/L also improved the scanvaging superoxide anion, and so reduced membrane lipid peroxidation and endocyte exosmosis; while the ability of root absorption on water and inorganic ion, scanvaging H2O2, protein express were enhanced insignificantly. These changes made mitigative effect of osmotic stress and inhibition on growth decended, and which may lead to NH4NO3 accumulation in the rhizosphere environment, even probable soil secondary salinization if it was serious. This study provided reference for the reasonable application of NH4NO3 to F. arundinacea planted in saline soil.