Effect of Native Azotobacter Chroococcum Strains on Growth and Uptake of Nitrogen and Phosphorus by Wheat Plant in Greenhouse Conditions

Azotobacter chroococcum can improve mineral nutrition of plants through N2 fixation and plant growth promoting capabilities. Fourteen strains of A. chroococcum were isolated from rhizosphere of wheat plants grown in different field conditions around Tabriz, northwest of Iran. In a pot culture experiment with sterile soil, wheat plants (Triticum aestivum cv. Falat) were inoculated with 14 bacterial strains. Positive control received nitrogen fertilizer without bacterial inoculation and the negative control was left un-inoculated and without N- fertilizer. Totally, 16 trearments with four replications were arranged in a completely randomized design. The plant growth indices and N and P concentrations of shoot and root were determined at the harvest time. Results showed that the inoculation with Azotobacter strains caused a significant increase in shoot and root dry weights. Bacterial inoculation significantly enhanced the concentration and content of N in shoot and root. Phosphorus content was only enhanced (p<0.05) in the root. Translocations of N and P from root to shoot were markedly increased in bacterial treatments compared to the positive and negative controls. Moreover, strains 1 and 48 which showed relatively higher phosphate solubilizing capability and phosphatase activity in in-vitro assay also brought about higher P content and concentration in shoot and its translocation from root to shoot.