Effects Of Salt Stress On Nitrogen Metabolism And Yield Of Rice

Soil salinization is one of the adverse factors affecting plant growth and development,and it even leads plant to death under severe condition.Nitrogen metabolism is one of the most important life activities in rice(Oryza Sativa L),and its metabolic process is influenced by many factors.Roots is the main organ of nitrogen absorption,the root morphology and root vigor of rice also affect the absorption and utilization of nitrogen.In this study,two rice cultivars named Mudanjiang 30(Sensitive cultivar)and Longdao 5(Salt-tolerant cultivar),which were treated with different salt concentrations(CK 0%,S1 0.075%,S2 0.15%,S3 0.225%,S4 0.3%)were used to study the effects of salt stress on root morphology and root vigor,the effects of salt stress on key enzyme activity of nitrogen metabolism in root,functional leaves and grain,the effects of salt stress on nitrogen accumulation,transport and distribution of rice.The aim were to reveal the mechanism of nitrogen metabolism in the ground and underground of rice response to salt stress,and to enrich the physiological basis of salinity tolerance in rice.The main conclusions were as follows:1.The root length,root surface area,root volume and root vigor of rice presented a single peak curve,the root length,root surface area and root volume peak occurred in heading stage,and the root vigor peak occyrred in booting stage.Compared with the ck,the root length,root surface area,root volume and root vigor of rice significantly decreased in bootng stage under salt stress.The relative root length,relative root surface area,relative root volume and relative root vigor in Longdao5 were larger than that of Mudanjiang30.Correlation analysis shown that,there was a significant positive correlation between root morphology,root vigor and nitrogen accumulation in leaves,stem+sheath and root system of rice.2.The activity of nitrate reductase(NR),glutamine synthase(GS),glutamate synthase(GOGAT),glutamate dehydrogenase(GDH)and the content of soluble protein in functional leaves and roots of rice presented a single peak curve,the peak of the key enzyme activity occurred in heading stage,the peak of soluble protein occurred in booting stage.Compared with the ck,the activity of NR,GS,GOGAT and the content of soluble protein in functional leaves of rice decreased under salt stress,but the activity of GDH increased under salt stress.The variation for key enzyme activity of nitrogen metabolism was increasing with the increase of salt concentration.The NR activity in functional leaves of two cultivars rice significantly decreased in the main growth stage under the treatment of S3 and S4.The decline of NR activity in functional leaves of Mudanjiang30 was highest in heading stage under the treatment of S3 and S4.,thedecline of NR activity in functional leaves of Longdao5 was highest in filling stage under the treatment of S3 and S4.The activity of GS,GOGAT in functional leaves of Longdao5 was higher than that of Mudanjiang30 in heading stage under the treatment of S2,S3 and S4.The content of soluble protein in functional leaves of Longdao5 was higher than that of Mudanjiang30 in booting stage and heading stage under the treatment of S2,S3 and S4.3.The variation for the activity of NR,GS,GOGAT,GDH,and the content of soluble protein in roots was basically consistent with the variation for functional leaves.Compared with the ck,the activity of NR,GS,GOGAT and the content of soluble protein in roots of rice decreased under salt stress,but the activity of GDH increased under salt stress.The variation for the activity of NR,GS,GOGAT and the content of soluble protein in roots was highest under S4 treatment.The decline of NR activity in roots of Mudanjiang30 was highest in heading stage,the decline of NR activity in roots of Longdao5 was highest in filling stage under S4 treatment.The activity of GS,GOGAT in roots of Longdao5 was higher than that of Mudanjiang30 in heading stage under S4 treatment.4.The activity of GS,GOGAT,GDH in grain presented a single peak curve.The peak of GS activity in grains of Mudanjiang30 was delay under treatment of S2,S3 and S4.The peak of GDH activity in grains of Mudanjiang30 was ahead under treatment of S2,S3 and S4.The peak of GDH activity in grains of Longdao5 was delay under salt treatment.The content of soluble protein in grains of rice presented a constant decrease after full heading.Compared with the ck,the activity of GS,GOGAT,GDH and the content of soluble protein in grains of rice decreased under salt stress(In addition to the GDH activity in grains of Longdao5 at the 28 th days after full heading stage),there were differences between varieties and treatments.5.The concentration of nitrate nitrogen and ammonium nitrogen in leaves,stem+sheath and roots of rice presented a single peak curve,and the peak occurred in heading stage.The concentration of nitrate nitrogen and ammonium nitrogen in grains presented a single peak curve,and the peak occurred in 21 th days after full heading stage.Compared with the ck,the concentration of nitrate nitrogen and ammonium nitrogen in leaves,stem+sheath and grains decreased under salt stress,the concentration of nitrate nitrogen decreased in roots,the concentration of ammonium nitrogen in roots increased,and there were differences between varieties and treatment.6.The nitrogen accumulation in leaves,stem+sheath and roots of rice presented a single peak curve.The nitrogen accumulation in grains increased from the heading stage to the maturity stage.Compared with the ck,salt stress significantly reduced the nitrogen accumulation in leaves,stem+sheath,grains and roots in the heading stage(in addition to the nitrogen accumulation in grains under S1 treatment).Salt stress significantly reduced the transport volume of nitrogen in leaves and stem+sheath of rice(in addition to the transport in stem+sheath under S1 treatment).Compared with the ck,the contribution rate of nitrogen transfer in stem+steath and leaves of rice significantly increased under S1 and S2 treatment,and the contribution rate of nitrogen transfer in stem+sheath and leaves of Longdao5 was significantly increased under S3 treatment.7.Compared with the ck,the yield decreased with the increase of salt concentration,and the yield of Longdao5 was not significantly decreased under S1 treatment,but the yield of Mudanjiang30 decreased significantly.The yield of two varieties rice significantly decreased under the treatment of S2,S3 and S4.Correlation analysis shown that there were a significant positive correlation between the activity of NR,GS,GOGAT in functional leaves and roots and yield in the tillering stage,bootng stage,heading stage and filling stage of rice.The GDH activity in functional leaves and roots was significantly negatively correlated with the yield.The root length,root surface area,root volume and root vigor were significantly positively correlated with the yield.