Response Of Soybean And Mung Bean To Low Temperature Stress And Regulation Mechanism Of Uniconazole At Early Flowering Stage

Chilling injury in summer is one of the main disastrous weather in Heilongjiang Province,which has a very serious impact on the yield of bean plants.Uniconazole（S3307）could improve the stress resistance of crops and increase the yield under abiotic stress and adverse environmental conditions as a growth retardant.In this paper,soybean（Kenfeng 16 and Hefeng 50）and mung bean（Lvfeng 5 and Lvfeng2）were taken as experimental materials,the principles and methods of comparative biology were used to study the similarities and differences of stress of different leguminous crops to low temperature stress at the early flowering stage（R1）from various aspects,and the mitigation mechanism of S3307 on soybean and mung bean under low temperature stress at the R1 stage was also explored.1.With the extension of low temperature stress time at the R1 stage,in terms of plant growth and development,the plant height,leaf area and dry matter weight of different soybean and mung bean varieties gradually decreased,the bottom pod height and stem diameter gradually increased,and the difference of each index was significant among different varieties.The application of S3307 to the leaves alleviated the reduction of dry matter weight under low temperature stress effectively,further reduced the plant height and leaf area of the two species,promoted the growth of stem diameter and controlled the growth of bottom pod height.The treatment of S3307 accelerated the recovery ability of crops and alleviated the damage caused by low temperature stress.2.With the extension of the low temperature stress time at R1 stage,in terms of plant productivity,the number of pods per plant,the number of seeds per plant,the weight of 100 seeds per plant and the yield per plant of soybean and mung bean all decreased.Exogenous application of S3307 could improve the yield per plant and alleviate the decline in the yield of soybean and mung bean under low temperature stress.3.With the extension of low temperature stress time at R1 stage,in terms of plant carbon metabolism,the net photosynthetic rate（Pn）and SPAD value of leaves of soybean and mung bean varieties decreased significantly.The activities of carbon metabolism related invertase（AI,NI,IN）and sucrose synthase（SS）increased significantly,while the activities of sucrose phosphate synthase（SPS）were significantly decreased,resulting in the gradual decrease of sucrose and starch content.Mung bean decreased more than soybean.S3307 significantly enhanced the photosynthetic effect indexes of soybean and mung bean under low temperature stress,and significantly alleviated the decline of SPS,sucrose and starch content.S3307 enhanced the resistance to low temperature by improving the carbon metabolism activity of plants.4.With the extension of low temperature stress time at R1 stage,in terms of plant physiological and biochemical indicators,the contents of malondialdehyde（MDA）,osmoregulation substances and abscisic acid（ABA）in soybean and mung bean increased,the activities of antioxidant related enzymes（SOD,POD,APX,GR）increased,and the contents of indoleacetic acid（IAA）,gibberellin（GA₃）,and zeatin（ZT）decreased significantly.S3307 treatment significantly inhibited the increase of MDA content,significantly promoted the decrease of GA₃ content and the increase of ABA,SOD,POD,GR,APX activity,and significantly alleviated the decrease of IAA content.The application of S3307 could improve the operation of antioxidant system,and promote the changes of endogenous hormones of plants to regulate their own balance to cope with low temperature stress.5.At the 4th day of low temperature stress at R1 stage,in the ultrastructure of soybean and mung bean leaves,the chloroplasts of soybean and mung bean leaves obviously expanded,and the inner membrane system disintegrated,mitochondria and starch grains gathered.The application of S3307 reduced the damage of leaf cells and had a good protective function on leaf cells of two crops.6.According to the transcriptome and metabolome analysis results,GO enrichment analysis of DEGs in soybean under low temperature stress for 4 days showed that they were mainly enriched in defense functions such as response to hydrogen peroxide,and the KEGG enrichment analysis results showed that they were mainly enriched in MAPK signaling pathway–plant and other defense metabolic pathways.However,GO enrichment analysis of DEGs in mung bean under low temperature stress for 4 days showed that they were mainly enriched in chloroplast and other functions,and the KEGG enrichment analysis results showed that they were mainly enriched in photosynthesis and other metabolic pathways,and more down-regulated DEGs enriched in them.The results of differential metabolite KEGG showed that the number of differential metabolites and metabolic pathways significantly enriched in soybean under low temperature stress was more than that in mung bean.It indicated that soybean had strong defense ability,and the damage under low temperature stress was less than mung bean.7.The combined analysis of transcriptome and metabolome showed that in DS＿vs＿CK and DS＿vs＿D the pathways enriched by common DEGs and common differential metabolites include metabolic pathways and biosynthesis of secondary metabolites.It was speculated that these two metabolic pathways increased the content of proline,lactose,malic acid and other metabolites in plants by increasing the expression of ZAT10,ELF3,PER12,ERF1B,WRKY33 and other genes.In the interaction network of soybean and mung bean,there were 51 and 60 common DEGs,transcription factors and differential metabolites involved in cold stress resistance,respectively,which were significantly positively correlated,it showed that S3307 can reduce the damage to plants caused by low temperature stress by regulating genes and metabolites to participate in carbon metabolism,and its regulation effect on mung beans was better than that on soybeans.