Effects Of Spraying Brassinolide(BR) On Photosynthetic Characteristics In Leaves Of Foxtail Millet(Setaria Italica L.) Under Sigma Broad Stress

Foxtail millet(Setaria italica L.)is an important edible and medicine cereal crop in China.However,there are many species of weeds in foxtail millet field,and it is a gramineous crops more sensitive to herbicide.So the weed is the main limiting factor to the foxtail millet production of large areas.Sigma Broad is a Sulfonylurea herbicides of good application in wheat field which can control almost all the gramineous and broadleaf weeds.Brassinolide(BR),a growth regulator,copes with various biotic and abiotic stresses in plants.The application of BR improve the resistance of plants to unfavorable factors such as herbicides.To explore the photosynthetic characteristics and the role of spraying BR on alleviating the tolerance of foxtail millet under Sigma Broad.with Zhangza 5 and Jigu 21 as materials,through pot experiments,we studied the photosynthetic physiological mechanism of different concentrations(0?7.5?15.0?30.0 and 60.0 mg-L-1)of 3.6%Sigma Broad aqueous solution(AS)on foxtail millet and foliar application different concentrations(0,0.01,0.1,1,2 mg-L-1)of BR after 7.5 mg-L-1 of Sigma Broad treatment The results showed that:1.Effects of Sigma Broad on photosynthetic physiological of foxtail milletSigma Broad significantly decreased plant height,leaf area,fresh mass,photosynthetic pigment content(Chla?Chlb?Car?Chl(a+b)),net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr),maximum fluorescence(Fm),the maximum photochemical yield(Fv/Fm),apparent photosynthetic electron transport rate(ETR),quantum yield dissipated by non-regulatory energy(Y(NO)),Phosphoenolpyruvate carboxylase(PEPC),NADP-malate dehydrogenase(NADP-MDH)and pyruvate orthophos-phate dikinase(PPDK)of Zhangza 5 and Jingu 21,but significantly increased intercellular CO2 concentration(Ci),Initial fluorescence(Fo)and the quantum yield dissipated by regulatory energy(Y(NPQ).With the increasing of Sigma Broad concentrations,the Soluble protein,Reducing sugar,Sucrose and starch content,NAD-malic enzyme(NAD-ME)and Ribulose bisphosphate carboxylase oxygenase(Rubisco)of foxtail millet increased and subsequently decreased.Sigma Broad has hindered photosynthetic pigment synthesis,inhibition of the reaction center of photosystem activity,breaking the normal operation of carbon cycle,protein metabolism and carbohydrates metabolism,decrease of net photosynthetic rate,and finally effect the growth and development of foxtail millet.Sigma Broad applied at a concentration of 7.5 mg-L-1 caused the minimal phytotoxicity of foxtail millet,the serious damage was caused by Sigma Broad at the concentration of recommended dosage(30 mg-L-1).In two varieties,Jingu 21 is more sentitive than Zhangza 5 under Sigma Broad.2.Effects of BR on photosynthetic physiological of foxtail millet under Sigma Broad stress1 day after Sigma Broad treatment,spraying BR could alleviates the injury of Sigma Broad on foxtail millet.With the increasing of BR concentrations,the main morphological index(plant height,leaf area,fresh mass),photosynthetic pigment content(Chla?Chlb?Car?Chl(a+b)),Pn,Gs,Tr,Fm,Fv/Fm,ETR,Y(I)?ETR(I)?Pm?Y(ND)?PEPC?NADP-MDH?PPDK?NI?SS ? SPS of Zhangza 5 and Jingu 21 increased and subsequently decreased,but Ci?Fo?Y(NPQ)?Y(NA)?the Soluble protein content,Reducing sugar content,Sucrose content,starch content,NAD-ME and Rubisco showed the opposite trend.0.1-0.2 mg-L-1 BR improved the photosynthetic pigment contents of leaves,alleviated the damage to photosystem reaction center,maintained the carbon cycle,protein metabolism and sucrose metabolism of foxtail millet under Sigma Broad stress,and ensured the balance between photosynthetical product synthesis and metabolic.Results of this experiment provide a theoretical basis and technological approaches for security application of sulfonylurea herbicide and the alleviation of herbicide phytotoxicity in foxtail millet field.