Effects Of Soda Saline-alkali Stress On Nitrogen Metabolism Mechanism And Yield Of Different Rice Seedlings

Soil saline-alkali stress is a complex environmental stress,which mainly leads to osmotic stress,ion poisoning and high pH environment.It affects the production of plant photosynthetic substances,the absorption and utilization of nutrients,and the growth and development of life activities.Nitrogen metabolism is a basic life activity of plants,and the plant's ability to regulate itself and external stress strongly influence its absorption and assimilation mechanism.In this study,Changbai 9 and Jijing 88 were used as experimental materials for hydroponic and potted plant experiments.Set three larvae of age:L1 for 3seedling-age;L2 for 4 seedling-age;L3 for 5seedling-age.The hydroponic test used a nutrient solution containing mixed salt of 50 mM NaCl,Na₂SO₄,Na₂CO₃,NaHCO₃ as a stress solution.Pot experiment with 4 concentration gradients:CK for natural black soil control;A1 for natural black soil:saline-alkali soil=2:8;A2 is natural black soil:saline soil=3:7;A3 is natural black soil:saline soil=4:6.The growth response and nitrogen metabolism regulation mechanism of rice in different ages under saline-alkali stress were studied.The main results are as follows:1.Saline-alkali stress significantly increased the proline and soluble sugar content in rice seedlings of different ages.The response time of the three-leaf seedlings was earlier,the increase was greater,the peak was higher,and there was a faster and more effective osmotic adjustment mechanism.With the increase of age,osmotic adjustment ability became weaker;saline-alkali stress significantly increased Na⁺accumulation and Na⁺/K⁺on the ground and roots of rice seedlings in all ages.The peak value of three-leaf seedlings was higher,and the ion balance ability gradually increased with the growth of seedling age..2.Saline-alkali stress significantly reduced nitrogen accumulation and dry matter accumulation in rice seedlings of different ages.The accumulation of material in the 3seedling-age was earlier,and the decrease was greater.The total dry matter accumulation of the5 seedling-age of Changbai 9 and the 4 seedling-age of Jijing 88 had no significant decrease in the stress time,and the accumulation amount kept a high level.3.The regulation of nitrogen uptake in rice seedlings of different ages under saline-alkali stress was different.The 3seedling-age and 4 seedling-age up-regulated the relative expression of OsNRT1;1 and OsNRT1;2 genes in response to saline-alkali stress;Significant upregulation of OsAMT1;1,OsAMT3;2 expression in leaves and roots,and OsAMT2;2,OsAMT2;3expression in in roots to promote NO₃^-and NH₄⁺uptake.5 seedling-age up-regulation expression of OsNRT1;1,OsNRT1;2 of the ground part,and the absorption of nitrogen is preferentially transported to the upper part to ensure the use of the upper part.And raised the expression of OsAMT1;2 to enhance the storage of ammonium to deal with saline-alkali stress.4.Saline-alkali stress significantly decreased the NR activity of all seedlings and reduced the expression of OsNR,the smaller the age,the greater the decline.Saline-alkali stress significantly weakened the GS/GOGAT assimilation pathways in all ages.After 48h of saline-alkali stress,the expression levels of OsGS2 and OsFe-GOGAT genes were significantly down-regulated in leaves of different ages,and the down-regulation of gene expression in3seedling-age was significantly greater than that in 5seedling-ages.At the same time,the expression levels of OsGS1;1,OsGS1;2 were also significantly down-regulated in the roots of3seedling-age.This further affects the material accumulation of 3seedling-age.The activity of GDH enzyme in leaves and roots of 3seedling-ages and 4seedling-ages was decreased after saline-alkali stress,but increased slightly in 5seedling-ages.Most of the OsGDH genes of 5seedling-age showed a slight increase in stress time.It is suggested that 5 seedling-age can adapt to the influence of salt and alkali stress on nitrogen uptake by enhancing GDH metabolism pathway.5.Under the control and mild saline-alkaline stress conditions,the 5seedling-age rice has higher effective panicles and grains per panicle,and the yield is higher.With the increase of saline-alkali,the yield of 4seedling-age rice is higher.The yield of rice at 3seedling-age was always the lowest under saline alkali stress.From the yield composition,the number of spikes,the seed setting rate and the 1000 grain weight were the main factors to reduce the yield.