Effect Of Low Temperature On Maize Emergence And Grain Filling And Chemical Regulation

In the north area of china,the frequent of chilling injury is one of the main natural disasters during maize production.Since the disaster covert and imperceptible,maize emergence,grain filling and yield has been seriously affected.In this study the cold condition is created by manual control the temperature indoor and adjusting the sowing date in the field.To research the influence mechanism of low temperature on emergence and seedling growth of corn and the mitigation effect of different chemical control by artificial climate chamber and early sowing in the field.To research the effect and mechanism of low temperature in grain filling stage on maize grain filling and the mitigation effect of chemical control through in vitro ear culture system and late sowing in the field.By studying the low temperature condition effect on grain sprouting status,seedling morpHology and pHysiological changes,matter accumulation,dry matter production and transport,late grain filling characteristics,starch synthesis,carbon metabolism enzyme activity,endogenous hormone changes and yield and the mitigation effect of different chemical control methods,in order to provide evidence for maize to make full use of heat resources in north,and achieve resilience and stable yield.The main results are as follows:1.The 6GA mixed compound is developed by using response surface optimization design method,its performance is superior to a single regulator,it can promote corn germination rate,germination potential,endosperm matter transport,morpHological index of radicle and germ,endogenous hormone content,seed amylase activity in endosperm and seedling soluble sugar content.In germination comparative tests of three varieties:Zhengdan 958,Dongdan 60 and Dongdan 90,the result shows that it has a good role in promoting Zhengdan 958 and Dongdan 90.In sand culture experiment under different length of time of low temperature stress,6GA can improve emergence rate and index of sand culture test,and it promotes seedling growth and development,stem and root elongation growth and coordinated growth,and maintains the reasonable root-shoot ratio during continuous low temperature environment,and after the return to normal temperature environment.2.6GA is applied in two sowing date on April 1 and April 15,it improves the emergence rate and index of early sowing maize.Compared with control the emergence rate applied in 6GA of three varieties Zhengdan 958,Dongdan 90,Dongdan 60 improved 8.9%,59.6%,14.4%,respectively.The function of 6GA in low temperature sensitive varieties is better than low-temperature tolerant cultivars.Using of 6GA can significantly improve the early sowing corn plant height and stem diameter during seedling stage,speeding up the leaf extension rate,increasing the total root length,average root diameter,root surface area,total root volume,improve the matter accumulation of root effectively and improve seedling root-shoot ratio.But as the delay of sowing date,the effect of 6GA is not significant.3.Under in vitro ear culture system and late sowing in the field conditions,it found that maize grain growing development during filling stage is greatly influenced by low temperature,grain dry matter accumulation in vitro culture performances NT>MT>LT and in the field sowing date test performance for 6/15>7/1>7/15.The result shows that the longer the duration of low temperature,the less biomass accumulation.Low temperature significantly prolonged the filling time,reduced the average filling rate and maximum filling rate,delayed the maximum filling rate appeared time,reduced grain theoretical maximum dry weight.Low temperature in grain filling period last longer,all of these reduced greater.The correlation between grain theoretical maximum dry weight and the maximum and average filling rate proves that,grain weight reduction is resulted from the influence of low temperature on filling rate.The low temperature reduced the grain starch content and decreased the activity of SAI,SS,SSS and APGase in the grain filling process,and the effect of inferior grains is larger than superior grains.In the early filling stage,the activity of SAI and SS decreased significantly,resulting in conversion of sucrose to starch synthetic substrate is blocked.The SSS and APGase activity decreased rapidly in the later filling stage,which affected the grain starch synthesis.Low temperature also reduces the content of IAA and GA,disrupts the content in the grain ZR and ABA,leading to grain growing development hindered during filling process,matter accumulation reduced,final grain weight significantly reduced,and a serious decline in production.4.After using BB and OP pHarmaceutical treatment,it increased the grain dry matter accumulation,the maximum and average filling rate,the efficiency of grain matter accumulation,slowed the starch accumulation rate of early stage under low temperature.It also increased the activity of SAI,SS,SSS,AGPase in grain under low temperature and more significant to promote carbon metabolism enzymes during late filling stage.In this process,grain endogenous hormones IAA,GA and ZR contents are significantly higher than control,and the change of ABA content by agent effects was not significant.The ear length of 7/15 sowing date is increased by the agent,with the increase of 1000 grain weight.During two sowing date,it performances for BB>OP>CK,which resulted in a significant increase in yield compared with the control.