Exogenous Melatonin On Soybean Under Drought Stressregulatory Effects Of Nitrogen Accumulation

Drought stress inhibits soybean growth and development,limits the rate of nitrogen assimilation and distribution,and affects the formation of soybean yield and quality.As a plant growth regulator,melatonin plays an important role in the physiological regulation of plants and the enhancement of stress resistance.However,at present,there is a lack of in-depth analysis of the mechanism of melatonin to promote soybean growth and yield increase under drought stress from the perspective of nitrogen accumulation.Therefore,this experiment was conducted in the rainproof greenhouse of the National Grain Technology Research Center of Heilongjiang Bayi Agricultural University from 2018 to 2019.50% of field water holding capacity was treated with drought stress,and 80% of field water holding capacity was treated with control.To study the effect of exogenous melatonin on the nitrogen accumulation of soybean under drought stress.The results showed that:1.Drought stress inhibits the growth and development of soybean plants and reduces the accumulation of dry matter in various organs.Exogenous spraying of melatonin under drought stress can alleviate the inhibitory effect of drought stress.Among them,the pods and grains at the pod setting stage are significantly different from drought stress on the 10 th and 17 th days of drought stress,which are increased by 17.78%,14.78% and 14.81% and 10.71%;the pods and seeds at the drum stage were significantly different on the 10 th day of drought stress,increasing by 14.29% and 16.67% respectively.2.Drought stress reduces the activities of key inorganic nitrogen assimilation enzymes NR,GS,GOGAT,GDH,GOT,and GPT of soybean plants at the seedling stage,flowering stage,pod stage,and drum stage.After 7 days of rehydration,except the drum stage The key enzyme activities of inorganic nitrogen assimilation in seedling stage,flowering stage and pod stage were all recovered,which were still lower than the control.Exogenous spraying of melatonin under drought stress can increase the activities of key enzymes of inorganic nitrogen assimilation at various growth stages of soybean plants.The activities of key enzymes of inorganic nitrogen assimilation increased significantly on the 10 th and 17 th days of drought stress.3.Drought stress significantly inhibited the nodule development and nitrogenase activity ofsoybean plants at the seedling stage,flowering stage,pod stage and drum stage.Exogenous melatonin can increase the quality,quantity and root nodule nitrogenase activity of soybean nodules at various growth stages under drought stress.The increase in drought stress on the 10 th and 17 th days was significant.4.Drought stress leads to increased nitrate nitrogen and ammoniacal nitrogen content in plant leaves,decreased urea content,and increased proline and soluble protein content.Exogenous spraying of melatonin under drought stress can significantly alleviate the toxic effects caused by excessive accumulation of nitrate nitrogen and ammoniacal nitrogen,while increasing the content of acyl urea,proline and soluble protein,and further alleviating the inhibitory effect of drought.Compared with drought stress,the nitrate nitrogen content at the seedling stage,flowering stage,pod stage and drum stage at the 10 th day of drought stress was significantly different,which were reduced by 15.96%,11.22%,12.32% and 19.46%,respectively.The content of acyl urea and soluble protein at the 10 th and 17 th days of seedling stage,flowering stage and podding stage,the difference reached a significant level.5.Drought stress inhibits the dry matter accumulation of various organs of soybean plants at the seedling stage,flowering stage,pod stage,and drum stage,inhibits plant growth,reduces nitrogen assimilation and transport capacity,and inhibits the growth of nitrogen accumulation of each organ After 7 days of rehydration,it recovered but was still lower than the control.Foliar spray of melatonin can alleviate the inhibitory effect of drought stress on the growth of soybean plants,promote the rate of nitrogen assimilation transfer,and then increase the accumulation of nitrogen in various organs.6.Drought stress reduces the number of pods per plant,the number of seeds per plant,the weight per plant,and the weight per 100 seeds of soybean plants at the seedling stage,flowering stage,pod stage,and drum stage.Exogenous spraying of melatonin increased the number of pods per plant,grain number per plant,grain weight per plant and 100-grain weight of soybean plants at various growth stages under drought stress.10.62% and 10.51%,the number of seeds per plant,the weight per plant and the weight per hundred of the seeds at drum stage increased by 10.26%,13.83% and 11.00% respectively,which was significantly higher than that of drought stresstreatment.