Alleviated Effects Of Exogenous EBR On High Temperature Stress And The Underling Physiological Mechanisms In Soybean

The soybean is one of important oil crops in china,an important source of high quality protein and human edible oil and fats.Heat stresses,especially those occurred during grain filling,cause severe grain yield losses.Importantly,heat stresses are predicted to become more and more frequent and severe due to the climate warming.The root system of soybean is not developed and growing in the hot summer and is more sensitive to heat stress.In recent years,due to global climate change,heat stress happens frequently,Heat strss has become an important limited factor on yield and quality of soybean.In this study,Nannong 99-6(Glycine max var.)were used to study the effect of heat stress on the physiological characteristics and yield of soybean at flowering stage,at the same time,and study the effects of exogenous EBR on the growth,physiological characteristics and yield of soybean at flowering stage.The result will help to elucidate the resistant mechanism of EBR and give some new sights for heat-resistant cultivation.The result is ad follow:1.Exogenous EBR induced the soybean seeding H2O2 accumulating fast,improved the activity of SOD.Exogenous EBR increased antioxidant enzymes activity and Fv/Fm,decreased relative electrolyte leakage rate and MDA content,alleviated lipid peroxidation of soybean leaves under heat stress.One of the optimal concentrations of EBR is 025?molL-1 on the leaf to induce soybean thermotolerance.2.Soybean plants often suffer from heat stress during the flowering pod stage that finally reduction of yield and quality droping.Therefore,this experimental is to investigate the effects of foliar applied EBR on protecting soybean from heat stress during the flowering pod stage.Our results showed that flowering pod stage heat stress significantly reduce the grain weight per plant,depressed the growth and biomass of soybean.Exogenous EBR significantly improved leaf area per plant and each organ of dry matter accumulation under the heat stress,meanwhile significantly improve pods per plant?seeds number per plant,Thus increased the soybean yield,the height was not obvious.3.Heat stress causing the content of protein,starch and soluble sugur decreased in grain,and the fat were increased,Exogenous EBR increased the content of protein starch and soluble sugur,the fat decreased in grain,acids ratio have changed.4.The heat stress result Ti,Pn,Gs decline,Ci increased,also cause Fv/Fm and ?PSII.Exogenous EBR relieve Pn reduce under heat stress,improve Gs,Ti,and Fv/Fm and ?PSII.For yield develop provide better source-sink ratio.5.The study also found that exogenous EBR increased antioxidant enzymes activity,decreased MDA,alleviated lipid peroxidation,delaying plant senescence.Heat stress reduced the ZR,IAA content,improve ABA content,GA3 content unremarkable in the grain.Exogenous EBR relieve ZR and IAA content decrease range,ABA content is still very high under heat stress of soybean leaf.These result indicated that exogenous EBR with suitable concentration possible though H2O2 and ABA accumulate induce soybean thermotolerance.Incresed antioxidant enzymes activity and photosynthetic rate amino acids ratio have changed.Each organ of dry matter accumulation increased,causing increased the final yield.At the same time exogenous EBR improve the grain quality.