| Aimed in increase resistance of cotton to salt-stress by treated with salt-relieving and plant growth promoting bacteria, 215 bacteria strains were isolated from the rhizosphere of cotton which planted in alkaline soil. Sand bed and pot experiment showed that 4 of the 215 bacteria strains could steadily increase cotton germination under salt stress. Strain Rs-198 which promoted highest germination rate of cotton was characterised as Pseudomonas.sp. Through the determination of cotton's physichemical factors under salt stress during the period of germination and shooting, strain Rs-198 could conqer the resistant of salt stressed cotton can be demonstrated. With inoculated Rs-198, MAD and antioxidant enzymes activities were increasede, especialy activities of enzyme CAT and POD.With assuring that inoculate strain Rs-198 can promote cotton growth under salt stressed conditions,a further study in growth promoting factors of Rs-198 were practised. The ability of dissolution insolubile phosphate by strain Rs-198 was related to cell growth and medium pH. HPLC analysis showed that the bacteria can secret six main organic acids which were citric, gluconi, malic, lactic, acetic and propionic acids and the highest concentration were 50.95, 1.02, 1.38, 1.11, 14.56 and 7.21 mM?L-1, respectively. It was clear that concentration of citric acids was much more than any other acids and took the responsibiliy for disolving insoluble phosphate. Strain Rs-198 could also secret IAA and the content during incubation was stimulated and reached to 10.77 mg·L-1 in 96 hour. CAS plate showed that strain Rs-198 could secret siderophore. Possibly solubilizing phosphate, secreting organic acids, IAA and siderophore took responsibility for promoting cotton growth.
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