To investigate the putative role of bacterial cytokinins in the
control of rhizodeposition, two strains B. subtilis were used: IB-22,
which produces, and IB-21, which does not produce, cytokinins. In
the initial culture media, cytokinin concentrations were low, but
gradually increased during bacterial growth of IB-22, reaching a
steady state level after two days of incubation (Fig. 2A). No cytokinin
accumulation was detected in the culture media of IB-21
(Fig. 2B).