Barrier Mechanism And Regulation Of Delayed ChillingStress To Maize Yield

Under the global climate change,the risk of chilling stress,especially delayed chilling stress,increased in northern spring maize region.However,the physiological mechanism of maize resistance to chilling stress lacks systematic research,and preventive and compensatory control technologies are lacking.In this study,the effects of delayed chilling stress on maize growth and development were systematically studied under field and greenhouse simulation conditions.On the basis of field optimization of control measures,the regulation mechanism of exogenous Spd on delayed chilling stress of maize was emphatically discussed.The main conclusions are as follows:(1)Maize cold-resistant varieties have the following characteristics:?Shortening the bud length ensures the germination performance of seeds,and the emergence of seedlings is fast and concentrated,and the uniformity is high;?Root system has stronger plasticity,which maintains the root diameter and absorption performance by shortening the root length,and ensures the accumulation of biomass;?Leaf maintains chlorophyll synthesis and maintains a higher light photosynthesis.In addition,there are "standby mode" and compensatory growth in leaf growth,short-term stagnation of growth under chilling stress and higher growth rate after temperature recovery;?Higher activity of antioxidant system and POD-dominated enzymatic system play a leading role.(2)Drought resistance exercise can increase yield by 11.7%under chilling stress,which is an effective prevent measure;exogenous spermidine can increase yield by 12.2%,which is an effective compensatory measure.(3)The protective mechanism of exogenous spermidine on maize under chilling stress was as follows:? After spraying Spd,the contents of ADC?ODC and SAMDC were significantly increased,the levels of Put were increased,the transformation of Put to Spd and Spin was promoted,the content of endogenous fSpd and free polyamines was increased;? The contents of DAO and PAO oxidase were increased at the early stage of stress,and the metabolite of H2O2 was used as a signal molecule;?The increase of endogenous fspd inhibited the activity of NADPH oxidase and reduced the production of reactive oxygen species,thereby protecting maize plants from oxidative damage under chilling stress.