Screening And Studying Plant Growth-promoting Potential Of Managanese-resistant Strains

Metal mining and waste discharge caused destruction and occupation of large numbers of land resources, and led to a regional heavy metal contamination, endangering human health and the sustainable development of mining industry. Phytoremediation is emerging as the most competitive bioremediation technology benefit from its unique superiority in recent years. The growth of plants was difficult because of poor physical composition, deficiency of nutrient and toxicity of heavy metal. Therefore, it becomes a novel hot spot of environmental field to enhance phytoremediation with various strengthening measures.Plant growth-promoting bacteria (PGPB) were defined as free-living soil, rhizosphere, rhizoplane, and phylosphere bacteria that, under some conditions, are beneficial for plants. Owing to its unique mechanisms, it has been reported to be the key elements for plant establishment under external stress conditions. Because of this background, The rhizosphere soil of the Chenopodium album Linn which grew on Xiangtan manganese tailings was selected as the object of the study. Five manganese-resistant strains were isolated from the rhizosphere of exarid plant through concentration gradient screening technique, and the cellular form, physiological and biochemical tests were conducted, as the growth conditions and growth-promoting potential of the strains were investigated.The results showed that strains numbered K1, K2, K3, K4 and K5 were isolated from the rhizosphere of the plant belonged to Planococcus, Rothia, Arthrobacter, Serratia, Bacillus respectively according to physiological and biochemical tests and 16S rDNA sequences.The results from the growth conditions experiments showed that stability and decline phases of five strains were in the same period except logarithmic and lag phases of them were slightly different. The optimal temperature range for growth of the strains were around 30℃, and the optimal pH range for growth of the strains were around 7.3. In addition, the optimal NaCl concentration range for growth of the four strains were 10 g/L except the optimal NaCl concentration of Arthrobacter sp (K3) was 5 g/LThe results of growth-promoting potential tests showed that only Bacillus sp (K5) could generate siderophore, and five strains all produced IAA but the output was low. Meantime, four strains had capacity of solubilizing phosphate except Planococcus sp (K1). Plant growth-promoting potential of five strains was tested from generating IAA. And the abilities above were proved by datum, but field experiment should be taken to study how these strains to promote the growth of plants in the future.