Abstract: [Objective] This paper aimed to explore the response of Populus×euramericana cv.‘Nanlin-895’ (NL-895) to nitrogen metabolism and mineral elements under co-inoculation with P. fluorescent and X. chrysenteron, to reveal the effects of interaction between phosphate-solubilizing bacteria and ectomycorrhizal fungi on poplar growth at the level of nutrient metabolism, so as to provide a theoretical basis for developing and exploiting the compound microbial fertilizer for poplar.[Method] A pot experiment was conducted to investigate the effects of co-inoculation with Pseudomonas fluorescent JW-JS1 and Xerocomus chrysenteron on the nitrogen metabolism (soluble protein contents, nitrate nitrogen contents and nitrate reductase activity) and mineral element contents of NL-895 poplar in the greenhouse.[Result] Both JW-JS1 or Xc single inoculation and JW-JS1 and Xc co-inoculation significantly increased the soluble protein contents, nitrate nitrogen contents and nitrate reductase activity of NL-895 Poplar, and improved its mineral element content, and then the treatment effect of co-inoculation was higher than single inoculations and the control. The soluble protein content, the nitrate nitrogen content and the nitrate reductase activity of NL-895 poplar increased 20.19%, 79.99%, and 33.08%, respectively after 30 days of co-inoculation, 76.76%, 106.62%, and 34.86% after 90 days of co-inoculation and 137.99%, 50.70%, and 59.89% after 150 days of co-inoculation, compared with the control. The contents of P, Mg, K, Ca, Mn and Zn of NL-895 Poplar increased 71.66%, 23.67%, 49.71%, 22.90%, 84.57% and 151.56%, respectively compared with the control after 150 days of co-inoculation. Correlation analysis showed that the height and stem diameter of NL-895 seedlings were positively correlated with nitrate nitrogen content after 30 days of co-inoculation (P<0.05), and the height of NL-895 seedlings was positively correlated with soluble protein content after 90 days of co-inoculation (P<0.05). The height of NL-895 seedlings was positively correlated with nitrate reductase activity and K contents (P<0.05) after 150 days of co-inoculation, and the stem diameter of NL-895 seedlings was positively correlated with P contents (P<0.05) and K contents (P<0.01) after 150 days of co-inoculation.[Conclusion] The co-inoculation of Pseudomonas fluorescent JW-JS1 and Xerocomus chrysenteron significantly improved the nitrogen metabolism and mineral element absorption of NL-895 poplar, thus promoting the growth of NL-895 poplar.

Key words: Pseudomonas fluorescent, Xerocomus chrysenteron, co-inoculation, nitrogen metabolism, mineral element, growth-promoting