| The physical and chemical characteristics of saline-alkaline soils show that saline-alkaline soils have higher salinity and higher pH,and lack of nutrients in the soil,thus affecting the normal growth of plants.Plant litter is one of the main nutrient sources in saline-alkaline soil.Cellulose is one of the main components of the plant litter.Cellulose-degrading bacteria in saline-alkaline soil may play an important role in promoting plant growth.In this study,nine strains of salt-tolerant cellulose-degrading bacteria have been screened in our laboratory.The effects of these salt-tolerant cellulose-degrading bacteria on the growth of salt-tolerant plants such as rice,sunflower,wheat and stargrass under saline-alkaline conditions have been determined.The results of this study are as follows:1.For six strains of actinomycetes Sn-1,Sn-3,Sn-23,DS-22,DS-23 and DS-30,only strain Sn-1 increased cellulase activity and xylanase activity at 150 mM NaCl,and its CMC activities,xylanase activities were 5.23×10-2 IU and 15.38×10-2 IU,respectively.The activities of other strains decreased with the increase of salt concentration.2.In the study of nitrogen fixation characteristics of tested strains,it was found that all strains grew slowly with the increase of salt.The IAA production of tested strains were decreased with the increase of salt concentration.Among them,the inhibition by salt for strains Sn-17 and Sn-18 were the most obvious,and their IAA production under 300 mM NaCl was lower than that under 0 mM NaCl condition.The production of IAA decreased by 76.75%and 66.41%respectively.The highest activity of Rubp carboxylase was strain DS-22,reaching 212.53 IU/L,while the lowest activity was strain Sn-18,117.22 IU/L.The results showed that salt concentration inhibited the growth-promoting and autotrophic characteristics of the strains with different degrees.However,under the conditions of 150 mM NaCl and 300 mM NaCl,the strains still have the promoting growth and autotrophic characteristics.3.The effects of these saline-alkali-tolerant cellulose-degrading bacteria on the growth of salt-tolerant plants such as rice,sunflower,wheat and stargrass under saline-alkali conditions were studied.In rice pot experiment,the growth indexes of rice treated by strains Sn-17,Sn-18,Sn-20,MIX1,Sn-1,Sn-3,Sn-23 and MIX2 were higher than those of the CK control.Especially,strains Sn-20 and Sn-1 had the obvious increasing effect on the dry weight of rice.The difference was significant?P<0.01?.In the pot experiment of sunflower,strain Sn-18 and strain Sn-3 had the obvious growth-promoting effects on the plant height,root length,dry weight,fresh weight,leaf width and chlorophyll content of sunflower.The dry weight of the Sn-18treatment group increased by 21.05%compared with that in control group?P<0.01?.In the pot experiment of wheat,inoculating the experimental strains on the wheat plant significantly improved the growth of the plant.Strain DS-23 had the most obvious promoting effect on wheat growth,which increased the dry weight of shoot by 126.13%?P<0.01?.Mix had the weakest growth-promoting effect in the mixed strain treatment group.In stargrass pot experiment,strain DS-23 had the most obvious promoting effect on the growth of stargrass,and had the strongest promoting effect on the dry weight of shoot,increasing by 39.40%,with the strain DS-30,Mix had the weakest growth-promoting effect.4.Degradation of Leymus Chinensis litters by cellulolytic strains were determined by buried bag method.After 45 days buried,the results showed that the degradation ability was Sn-1>Sn-3>mix1>Sn-20>Sn-23>mix2>Sn-18>Sn-17>CK.It was concluded that the degradability of actinomycetes to Leymus Chinensis was higher than that of bacteria,which might be related to cellulase activity and xylanase activity of the strains.Studying the traits of cellulolytic bacteria related to plant growth promotion in saline-soil is great significance to the development,utilization of saline-alkali soil and the improvement of agricultural yield. |
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