Physiological Response Mechanism Of Different Soybean Varieties Resistant To Drought And Salt Stress

As a large country in agricultural production,agriculture has always been the national strategic and basic core industry in China.Soybean,as one of the important crops,its yield and quality directly affects the national food security.Drought stress and salt stress,which will seriously affect its yield and quality,are often faced during the growth and development of soybean.The two stress mechanisms of plants have some similarities.Therefore,In this study,drought resistance and salt tolerance mechanisms of soybean were studied from physiology,biochemistry,molecules and hormone treatments on drought tolerant variety CV.FD92(RD)and sensitive variety CV.Z1303(SD).The main findings are just as follows:The growth of RD and SD seedlings were inhibited by drought stress and salt stress to varying degrees,but the growth status of RD seedlings was better than that of SD seedlings,which showed the symptoms of wilting and yellowing of leaves.And the area of RD leaf was also increased by 28.1%and 29.6%compared with that of SD plants;the change of root system parameters also made answer to the adversity of environment.Under drought conditions,the total root length of RD plants increased by 66.4%compared to the total root length of SD plants,and the root surface area of RD plants was 1.64 times that of SD.Except that,compared with SD plants,the dry weight and root crown of RD plants increased by72.4%,160.7%and 48.8%,respectively.Under salt stress,the characteristics of root and growth parameters of RD plants were similar to those under drought stress,and all parameters were significantly better than those of SD plants.And the root crown of RD plants was 23.3%higher than that of SD plants.It can be seen that the growth parameters of the drought-resistant RD plants are more suitable for the adversity stress environment.Under drought and salt stress,plants regulate their osmotic regulatory substances and the concentrations of enzymes related to stress to change water potential,to increase their water absorption from the environment,thus maintaining antioxidant balance.Compared with SD plants,the contents of SOD and POD in RD plants,under drought stress and salt stress,were increased by 72.41%,175.00%and 131.10%,150.00%,respectively,and differences were all extremely significant;meanwhile,the MDA content in RD plants 26.70%and 52.70%lower than that in SD plants.Respectively,both them reached significant levels.In addition,under the same conditions,the K~+/Na~+in RD plant leaves was 2.81 times and 3.25 times higher than that in SD plants,and 1.25 times and 1.80 times in roots higher than that in SD plants.It is speculated that the regulation of K~+/Na~+ratio and increasing SOD and POD content to reduce MDA content in RD plants are one of the important strategies for resisting drought and salt.In order to further study the molecular mechanism of drought tolerance,the expression patterns of genes related to drought tolerance and the changes of hormone content in the plants were analyzed.The expression of GmP5CS in RD and SD was 8.00 and 1.20 times higher than that in the control group under the drought condition.The expression of GmP5CS in RD and SD under salt stress was 6.50 and 1.10 times higher than that of the control group.In addition,the expression profile of GmDREB1a tended to be similar in RD and SD were3.30 and 1.10 times higher than those in the control group under drought conditions,under the condition of salt stress were 4.00 times and 1.50 times respectively,the three other related expression levels of genes GmGOLS,GmBADH and GmNCED1 were basically consistent with the expression patterns of the above two genes.The ABA content in RD plants under drought and salt stress increased by 10.00 and 9.00 times,respectively,while in SD plants they increased by 4.60 and 3.00 times,respectively,in SD plants.During stress treatment,the amounts of JA and SA in both RD and SD decreased slightly,and the SD genotype decreased more.It can be seen that soybean can resist salt by regulating the physiological process of stress response by regulating the concentration of endogenous hormones such as abscisic acid(ABA),jasmonic acid(JA),and salicylic acid(SA).