Effects Of High Temperature During Flowering On Dynamics Of Flowers And Pods Of Soybean

Soybean can provide high quality protein and oil for human beings,and it is also one of the important sources of energy for animals.Soybean is a summer crop.With the global warming and the frequent occurrence of high temperature weather,soybean cultivation and production are greatly affected by high temperature.Extreme high temperature weather often occurs in some areas of China from July to August,which is the key period of soybean flowering.High temperature in flowering period will seriously affect the flower bud differentiation and flower and pod dynamic process of soybean,and finally cause great loss to soybean yield.Therefore,it is particularly important to explore how high temperature affects the development of flowers and pods and how high temperature affects the late pod setting and yield.In this experiment,suike 12 was used as the experimental material to study the effects of high temperature at flowering stage on flower and leaf temperature,pollen activity,flower and pod anatomical structure,leaf-flower-pod oxidative stress,flower and pod dynamics and yield composition of soybean by pot experiment in greenhouse.The aim was to clarify the physiological mechanism of high temperature at flowering stage on flower and pod dynamics and yield formation of soybean,and to provide theoretical basis for high temperature resistant cultivation of soybean.The test results show that:1.Under different treatment conditions,the canopy temperature and flower leaf temperature of R2H were higher than those of CK;under the same treatment condition,the flower temperature was about 2℃higher than leaf temperature,which was due to the lack of stomata in the flowers and the inability of transpiration.The results showed that the canopy temperature and the temperature of flower and leaf increased under high temperature,and the flower was more vulnerable to high temperature.2.High temperature stress can affect the process of flower bud differentiation and fertilization.For the flowers under high temperature and after high temperature,if the pollen grain formation stage of flower bud differentiation are exposed to high temperature for one day,the germination of pollen tube will be blocked;if the pollen grain formation stage of flower bud differentiation are exposed to high temperature for two or more days,the pollen tube will not germinate and the pollen will be deformed,resulting in the failure of fertilization and flower falling of soybean.For flowers before high temperature,even if flower bud differentiation did not encounter high temperature,high temperature stress affected the process of flowering and fertilization after flower bud differentiation,resulting in poor ovary development,internal collapse and flower falling.3.High temperature stress at flowering stage could significantly increase the contents of hydrogen peroxide（H₂O₂）and malondialdehyde（MDA）in leaves at that time,but there was no significant difference in the contents of hydrogen peroxide（H₂O₂）and malondialdehyde（MDA）in leaves at pod stage,indicating that high temperature at flowering stage had no significant effect on the"source"at later stage.High temperature stress at flowering stage also caused oxidative stress in flowers,which increased the contents of hydrogen peroxide（H₂O₂）,malondialdehyde（MDA）,superoxide anion（O₂^-）and superoxide dismutase（SOD）,especially in flowers before and during high temperature.At pod stage,the contents of hydrogen peroxide（H₂O₂）and malondialdehyde（MDA）in pod still increased significantly,with the same trend as that in flower,the pod formed by flower before and during high temperature increased most significantly.The results showed that high temperature at flowering stage only affected the source at that time,but the effect on flower could last until pod stage.The effect of high temperature on sink was persistent and aftereffect.4.High temperature can make the xylem cells inside the pod stalk collapse and disintegrate into filamentous structure,which affects the transportation of water and minerals and leads to pod dropping;the number of vascular bundles in the pod shell becomes less and the spacing becomes larger,which affects the transportation of photosynthetic products to the seeds,hinders the transportation of"flux"substances and leads to pod dropping;it also causes the cells inside the seeds to break up,increases the number of empty and seedless pods and decreases the weight of seeds.Therefore,high temperature can reduce the number and quality of pods on the main inflorescence,and cause serious damage to the"sink",so that the accessory inflorescence can enhance the compensation effect and supplement the yield by increasing the number and rate of pods.5.From the point of view of source,sink and flux,the high temperature at flowering stage only affects the source of the early stage,and has no obvious influence on the source in the later stage.High temperature mainly damages soybean"flux"and"sink",which results in more falling flowers and pods,more empty pods and seedless pods,less full pods and effective pods,lower number of seeds per pod and lower seeds weight,which affects the number and quality of sink,and eventually leads to the decline of yield,and the accessory inflorescence can not make up for the yield loss caused by high temperature.