Effect Of Chitosan On Nodulation,nitrogen Fixation And Sucrose Metabolism Of Vegetable Soybean Under NaCl Stress

A large number of studies have shown that chitosan can alleviate plant stress,but the research on nodulation ability and regulation mechanism of Chitosan on legume plants,especially vegetable soybean,under salt stress is still blank.Therefore,the effects of Chitosan on nodulation and nitrogen fixation,sucrose metabolism,root accumulation and dynamic changes with nodulation process of vegetable soybean under salt stress were studied in order to clarify the alleviating effect of Chitosan on inhibition of nodulation and nitrogen fixation of vegetable soybean under salt stress,and to explore the physiological regulation function of Chitosan on nodulation ability of vegetable soybean.The main results are as follows:1.Salt tolerance screening of vegetable soybean:18 vegetable soybean varieties collected were screened for salt tolerance,and two salt tolerant varieties' Luling No.8'and' ideal M-7',two salt sensitive varieties' Nippon Qing' and 'tezaoxian',and the rest were medium salt tolerant varieties.2.Symbiotic matching research:through the research on the symbiotic matching of vegetable soybean varieties' Lvling 8 'and' Nippon Qing 'with soybean rhizobia,the strains with better symbiotic effect and higher nitrogen fixation activity were screened out from 10 soybean rhizobia strains,which were slow-growing Rhizobium usda 122 matching' Lvling 8' and fast-growing Rhizobium HH103 matching' Japanese green'.3.Effect of Chitosan on nodulation and nitrogen fixation of vegetable soybean under salt stress:the results showed that salt stress had a significant inhibitory effect on nodulation and nitrogen fixation of vegetable soybean,while chitosan treatment significantly increased the nodule number,nodule fresh weight,nitrogenase activity,nitrogen content and plant dry weight of the two varieties under salt stress.Under the condition of no salt,chitosan had significant inducing effect on nodulation and nitrogen fixation of two vegetable soybean varieties,and significantly improved their underground.dry weight.The results showed that chitosan could significantly induce nodulation and nitrogen fixation of vegetable soybean under salt stress and without salt,and chitosan could alleviate the damage of vegetable soybean by promoting nodulation and nitrogen fixation.5.Effects of Chitosan on sucrose metabolism of vegetable soybean under salt stress:the results showed that chitosan significantly promoted the formation of reducing sugar and sucrose in roots and leaves of two vegetable soybean varieties.At the same time,chitosan significantly enhanced the activities of AI,Ni and SPS in roots and leaves of the two varieties of vegetable soybean.The activity of SS(Synthesis direction)enzyme activity in leaves and SS(decomposition direction)enzyme activity in roots were significantly enhanced.The results showed that:under salt stress,chitosan promoted sucrose synthesis and increased sucrose content in leaves by enhancing SS(Synthesis direction)and SPS enzyme activity in vegetable soybean leaves.At the same time,chitosan promoted the transportation of sucrose to roots and increased sucrose accumulation in roots.When sucrose accumulated in the root,chitosan promoted the decomposition of sucrose by enhancing the activities of SS(decomposition direction),AI and Ni enzymes in the root of vegetable soybean,thus providing sufficient energy for the growth and development of nodule in the process of nodulation,and finally enhanced the nodulation ability of vegetable soybean under Salt Stress.