Effect of exogenous 6- benzylaminopurine (BAP) on cellular cytokinin signaling. BAP treatment (application with 10 μM BAP-enriched medium) led to an increased TCS:GFP signaling compared to transformants maintained in the standard cultivation medium (control). (A) Graph represents the relative average mean gray values (MGV) of the TCS:GFP transformed BY-cells. Error bars represent standard error (n = 60). Statistical significance was evaluated with the unpaired student T-test (* P < 0.05, ** P < 0.01, *** P < 0.0001). (B) Representative pictures show the TCS:GFP signal intensities of 10 untreated (left) and BAP treated (right) transformed cells. (C) Graph depicts the change in relative number of transformed cells displaying a low (-), medium (+), high (++), and very high (+++) TCS:GFP signal intensity between the two samples (for detailed description of the quantification, see Additional file 1: Figure S2). Error bars represent standard error (n = 3 repetitions with at least 50 counted cells). Statistical significance was evaluated with the ANOVA test; the P-value is indicated.