Abstract

RODRIGUEZ-ANDRADE, Osvaldo et al. The decrease in the population of Gluconacetobacter diazotrophicus in sugarcane after nitrogen fertilization is related to plant physiology in split root experiments. Rev. argent. microbiol. [online]. 2015, vol.47, n.4, pp.335-343. ISSN 0325-7541.  http://dx.doi.org/10.1016/j.ram.2015.09.004.

It has been established that a decrease in the population of Gluconacetobacter diazotrophicus associated with sugarcane occurs after nitrogen fertilization. This fact could be due to a direct influence of NH₄NO₃ on bacterial cells or to changes in plant physiology after fertilizer addition, affecting bacterial establishment. In this work, we observed that survival of G. diazotrophicus was directly influenced when 44.8 mM of NH₄NO₃ (640 mg N/plant) was used for in vitro experiments. Furthermore, micropropagated sugarcane plantlets were inoculated with G. diazotrophicus and used for split root experiments, in which both ends of the system were fertilized with a basal level of NH₄NO₃ (0.35 mM; 10 mg N/plant). Twenty days post inoculation (dpi) one half of the plants were fertilized with a high dose of NH₄NO₃ (6.3 mM; 180 mg N/plant) on one end of the system. This nitrogen level was lower than that directly affecting G. diazotrophicus cells; however, it caused a decrease in the bacterial population in comparison with control plants fertilized with basal nitrogen levels. The decrease in the population of G. diazotrophicus was higher in pots fertilized with a basal nitrogen level when compared with the corresponding end supplied with high levels of NH₄NO₃ (100 dpi; 80 days post fertilization) of the same plant system. These observations suggest that the high nitrogen level added to the plants induce systemic physiological changes that affect the establishment of G. diazotrophicus.

Keywords : Nitrogen fertilization; Bacterial population; G; diazotrophicus; Sugarcane; Plant growth promoting bacteria.

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