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Open Access Publications from the University of California

Department of Plant Sciences

UC Davis

Influence of associative bacteria on root morphology of Arabidopsis plants in dependence on the supplied nitrogen form


Plant growth-promoting microorganisms (PGPR) colonize the rhizosphere of many plant species and stimulate plant growth either by fixing atmospheric nitrogen or by releasing phytohormones. To date, plant growth promotion by associative bacteria has resulted in poor reproducibility. Among several factors that affect the efficiency of the bacterial association, the use of different nitrogen forms has received little attention. It was the aim of this study to investigate whether root growth promotion by PGPR depends on the presence or availability of certain nitrogen forms and concentrations, different bacteria concentrations and phases of growth, and to investigate mechanisms which are responsible the positive effect of inoculation by bacteria.

In our studies Arabidopsis thaliana was inoculated with Raoultella terrigena and Azospirillum brasilense and cultivated under axenic conditions on agar plates. Dry weight of shoots and roots and root morphology were influenced positively in inoculated plants in dependence on the concentration and growth phase of inoculated bacteria as well as the nitrogen concentration and form, which was supplied to the growth medium. Especially root morphology of inoculated plants was strongly altered, which was expressed in an enhanced main root length, number of lateral roots and lateral root length.

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