Regulation Effects Of Uniconazole On Soybean At R1 Stage Under Low Temperature Stress

Low temperature stress is one of the main stress factors of soybean production,to clear the beginning flowering low temperature stress on the influence of soybean and effect of the regulation and control effect.The experiment was carried out in 2019 in a potted plant and its greenhouse of Heilongjiang Academy of Agricultural Sciences.The two soybean varieties and Hefeng 50 and Kenfeng as experimental material,using pot cultivation way research material leaves the beginning flowering soybean under low temperature stress（15℃）relative chlorophyll content,photosynthetic parameters,carbon metabolism related indicators,reactive oxygen species and their removal system,osmotic regulation substances and regulatory role of yield and yield components.The main test results and conclusions are as follows:1.The photosynthetic parameters of relative chlorophyll content,net photosynthetic rate,transpiration rate and stomatal conductance of soybean leaves of the two cultivar were reduced significantly by low temperature stress at the beginning of flowering period.Among them,the net photosynthetic rates of the two cultivar decreased by 26.39% and 20.12% at the 4th day of low temperature stress,respectively,compared with those of their respective controls.The content of starch and sucrose in leaves decreased gradually,the activity of invertase and sucrose synthase（SS）increased gradually,and the activity of sucrose phosphate synthase（SPS）decreased gradually.Compared with only low temperature treatment,S3307 treatment before low temperature stress can increase the above photosynthetic parameters,starch and sucrose content,activity of sucrose synthase activity and sucrose phosphate synthase,and reduce the invertase activity,but it is still significantly higher than the control.2.Low temperature stress at the beginning of flowering period significantly increased O₂^-·production rate,H₂O₂ content and MDA content of leaves of the two varieties of soybean.Enhanced the activity of SOD,POD,APX and GR,reduced the activity of CAT,increased the content of ascorbic acid（As A,DHA）,glutathione（GSH,GSSG）,and increased the content of soluble sugar,soluble protein and proline.Compared with only low temperature treatment,S3307 treatment before low temperature stress can reduce the contents of reactive oxygen species,malondialdehyde（MDA）in soybean leaves,and further improve the activity of protectiveenzymes,the content of ascorbic acid,soluble sugar,soluble protein and proline,and reduce the glutathione content,but it is still significantly higher than the control.3.At the beginning of flowering stage,the low temperature stress significantly reduced the number of pods per plant,the number of grains per plant and the yield of two soybean varieties.The longer the low temperature treatment time is,the larger the yield reduction range is.Spraying S3307 can reduce the yield reduction range of two soybean varieties under low temperature stress.In the four days of low temperature treatment,the yield of Hefeng 50 and Kenfeng 16 decreased by 13.17%,21.16%,22.73%,29.90% and 11.47%,18.57%,21.51% and26.34% respectively compared with the control.The yield of S3307 treatment increased by5.90%,8.40%,11.84%,16.30% and 8.95%,6.39%,8.85% and 16.09% respectively.In summary,foliar spraying S3307 can alleviate the effect of low temperature stress on soybean at R1 stage.By increasing the activity of antioxidant enzymes,the content of ascorbic acid and the content of osmotic regulatory substances,the contents of reactive oxygen species（ROS）and malondialdehyde were reduced,the ROS metabolism balance was maintained,and the damage of low temperature stress on the peroxidation of soybean leaf membrane was reduced.By increasing the chlorophyll content and photosynthetic capacity of soybean leaves,decreasing the activity of invertase,increasing the activity of synthase,increasing the content of starch and sucrose,thus decreasing the yield of soybean under low temperature stress.Therefore,spraying S3307 before low temperature treatment can alleviate the damage caused by low temperature stress on soybean and enhance the tolerance of soybean under low temperature stress.