Screening Of Cold Resistance At Bud Stage Of Maize And Effect Of Brassinolide On Seedling Under Low Temperature Stress

Heilongjiang province is located in the northeast of China and is an important grain production base in China.However,with the intensification of cold damage caused by extreme weather,the growth and development of crops are seriously affected and the yield of crops is limited.Maize is a thermophilic crop,cold injury will lead to delayed germination,seedling growth inhibition,produce yellow,wilting,necrosis and other symptoms,and even death.Brassinolide(BR)is a new kind of plant hormone which can alleviate abiotic stress.Most research have focused on alleviating or mitigating damage to horticultural crops by abiotic stress.Therefore,this experiment used 20 maize hybrids in Heilongjiang Province as experimental materials,through the preliminary cold resistance screening,to determine the cold tolerance classification of the varieties,to research the effects of low temperature on the physiological of cold and cold sensitive varieties with exogenous BR application.To explore the effects of low temperature stress and exogenous BR on the physiological characteristics of maize during germination and seedling stage,and to explore the most suitable application concentration of BR,and provide reference for solving the problem of low temperature and cold damage in production.The major results were as follows:1、The 20 maize varieties were initially divided into three categories by screening tests for at the germination stage.Class Ⅰ materials are:Yinongyu10,Lvdan2,Xianyu335,Demeiya 3,Demeiyal,Dade317,Jinong108,Demeiya2,Keyu17,Fuyuan2,Xinxinl,Shengyuan80,Xianyu696 and Xinkeyu2,which are characterized by anti-cold intermediate type;Class Ⅱ materials are:Longdan38,Hetian4 and Tianhel,which It is characterized by anti-cold sensitivity;Class Ⅲmaterials are:Tiannongjiu,Shuiyu23 and Nanbei4,which are resistant to cold and high resistance.2、Low temperature stress has significant inhibitory effect on maize germination,and there are significant differences among different cold resistance varieties.After soaking with different concentrations of BR,the germination time of TiannongJiu,Tianhel could be significantly shortened,and the inhibition of maize germination by low temperature stress was alleviated.The optimal concentration was 0.1 mg/L.3、Low temperature can significantly reduce the biomass above and below the corn seedlings.The growth of the above-ground shoots was the most inhibited in the early stage of low temperature stress,and the growth of the shoots was the most inhibited in the late stage of low temperature stress,and they all had the strongest growth ability in the late stage of recovery.BR can inhibit the growth of seedlings under low temperature stress,and 0.1 mg/L is the most suitable concentration.4、Low temperature can significantly reduce the SPAD value,Pn,Tr,gs of maize seedlings,increase Ci,destroy chloroplast structure and reduce photosynthesis efficiency.Photosynthetic system was most inhibited in the late stage of low temperature stress,and had the strongest growth ability in the early stage of restoration.Tianhe No.1 was more affected by low temperature stress.BR can enhance the cold resistance of maize seedling photosynthesis system by increasing the normal operation of the photosynthetic system of maize seedlings.0.1 mg/L is the most suitable concentration for the regulation effect.5、Low temperature can significantly increase the antioxidant enzyme activities of POD,SOD,CAT and MDA content of oxidative damage substances in maize seedlings.The contents of antioxidant enzymes and MDA increased rapidly in the early stage of low temperature stress,and the activity of antioxidant enzymes decreased rapidly in the early stage of recovery,while the difference of MDA content in recovery period was not significant.BR can alleviate low temperature injury by increasing the protective enzyme activity of maize seedlings and reducing the content of oxidative damage substances.0.1 mg/L is the most suitable concentration for the regulation effect.6、Low temperature can promote the increase of proline,soluble sugar and soluble protein content in maize seedlings and rise the relative conductivity of seedlings.Osmotic adjustment substances rise faster in the early stage of low temperature stress and decrease rapidly in the early stage of recovery.After BR spraying,the content of proline,soluble sugar and soluble protein in seedlings can be significantly increased,the cell osmotic balance can be maintained,the stability of cell membrane structure can be maintained,the relative conductivity of seedlings can be reduced,and the water loss of seedlings can be alleviated and reduced.Seedling injury,0.1 mg/L is the most suitable concentration for the regulation effect.7、Low temperature significantly reduced the content of IAA,GA and ZR hormones in maize seedlings and increased the content of ABA hormone.Exogenous spraying of BR can effectively alleviate the decrease of IAA,GA and ZR hormone content,reduce ABA content,increase the ratio of IAA/ABA,GA/ABA and ZR/ABA,and 0.1 mg/L is the most suitable concentration for the regulation effect.8、For the test materials with different cold resistance,the seed germination and plant performance are different under low temperature stress,and the low temperature mitigation ability is different after applying BR treatment.The cold-tolerant hybrid Tiannong 9 was less inhibited by low temperature than the cold-sensitive variety Tianhe No.1,and the former was stronger than the latter.The application of BR treatment can enhance the ability of maize to resist low temperature growth,and the effect of using Tiannongji is better than Tianhe No.1..