外源褪黑素对淹水胁迫下不同抗性玉米幼苗耐涝性的影响OA

[Objective]The study investigated the effects of exogenous melatonin(MT)on the waterlogging tolerance of maize seedlings under waterlogging stress.The aim was to clarify the regulatory mechanism by which MT alleviated waterlogging-induced damage in maize,screen for an optimal concentration,and provide a theoretical basis for breeding waterlogging-tolerant maize varieties and developing efficient cultivation practices.[Method]The waterlogging-sensitive inbred line Xian 21A and the waterlogging-tolerant inbred line SP221 were used as experi-mental materials,and a control group and stress groups were established.Waterlogging stress was simulated at the three-leaf stage of the seed-lings.The leaves were sprayed with either distilled water or MT solutions at concentrations of 50,100,150 and 200 μmol/L.Growth and phys-iological indices were measured on the 3rd and 5th days of waterlogging stress,followed by correlation analysis.The waterlogging tolerance of maize seedlings under different treatments was comprehensively evaluated using principal component analysis and the membership function method.[Result]Waterlogging stress significantly inhibited the growth of maize inbred lines.Oxidative damage intensified with prolonged stress duration,and the waterlogging-sensitive inbred line suffered more severe damage than the waterlogging-tolerant line.Under waterlogging stress,foliar application of an appropriate concentration MT increased plant height,stem diameter,leaf area,and the relative chlorophyll con-tent(SPAD value)in maize seedlings under waterlogging stress.It also reduced the contents of superoxide anion(O2-·)and hydrogen per-oxide(H2 O2),while enhancing the activities of superoxide dismutase,peroxidase,catalase,and ascorbate peroxidase,as well as the contents of soluble protein,soluble sugar,and proline.The waterlogging-tolerant inbred line exhibited higher sensitivity to MT application than the wa-terlogging-sensitive line.Correlation analysis showed that the SPAD value was significantly positively correlated with catalase activity and ex-tremely significantly positively correlated with soluble protein content,while it showed a significant negative correlation with H2O2 content.These results indicated that MT alleviated reactive oxygen species accumulation by activating the antioxidant enzyme and osmotic adjustment system,thereby increasing chlorophyll content.Comprehensive evaluation revealed that exogenous MT enhanced the waterlogging tolerance of maize seedlings.Under 3-day waterlogging stress,the optimal treatment for the waterlogging-sensitive inbred line was 200 μmol/L MT,where-as 100 μmol/L MT was optimal under 5-day stress.For the waterlogging-tolerant inbred line,100 μmol/L MT was the most effective treatment under both 3-day and 5-day waterlogging stress.[Conclusion]Exogenous MT effectively regulates the maize defense system in response to wa-terlogging stress,with 100 μmol/L being the optimal spray concentration under prolonged waterlogging stress.