Mechanism of Exogenous Brassinolide in Alleviating Drought Stress Injury at Panicle Differentiation Stage in Foxtail Millet
A pot experiment was conducted to investigate the regulatory effects of brassinolide on photosynthesis,antioxidant systems,and nitrogen metabolism in the high-quality foxtail millet variety,Jingu 21,under drought stress during panicle differentiation.Three treatment groups were established:a normal control(CK),a drought stress after water spraying(DS),and a drought stress after brassinolide spraying(BR).Upon reaching panicle differentiation,the treatment groups were separately sprayed with water and 0.1 μmol/L brassinolide on the leaf surface.After the cessation of drought stress,parameters including photosynthesis indices,hydrogen peroxide(H2O2),malondialdehyde(MDA)contents,osmotic regulators,antioxidant enzyme activity,nitrogen metabolism key enzyme activity,yield,and its components were measured and analyzed for all treatments.The results showed that drought stress significantly impeded the growth and development of foxtail millet during the panicle differentiation stage,but the application of exogenous brassinolide could mitigate these adverse effects.Yield and grain weight per panicle were increased by 17.29％and 8.62％,respectively,while the empty seed rate was decreased by 18.46％.Several parameters like net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr),chlorophyll content,superoxide dismutase(SOD),catalase(CAT),peroxidase(POD)activities,soluble sugar,free proline,nitrate reductase(NR),glutamine synthase(GS),glutamate synthase(GOGAT),and glutamate dehydrogenase(GDH)activities increased to varying degrees.H2O2 and MDA contents were significantly reduced.Consequently,spraying 0.1 μmol/L brassinolide could alleviate the reduction of foxtail millet growth and yield under drought stress during panicle differentiation period by increasing photosynthesis,chlorophyll content,osmotic regulators,antioxidant enzymes,nitrogen metabolism enzymes,and reducing reactive oxygen species and MDA content,facilitating reactive oxygen radicals scavenging,and maintaining the balance of carbon and nitrogen metabolism in the plant.
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