Fig. 3
Adventitious root formation 384 hpe with cuttings of Petunia hybrida: (Panel a) Root number per length class (RNC) with two levels of total nitrogen content (Nt) (cycles = N-low, squares = N-high). (Panel b) RNC response to dark exposure (squares = dark, cycles = no dark). (Panels c and d) Response of total root number (TRN) and total root length (TRL) on combinations of two Nt levels and dark exposure (striped bars = no dark, full bars = dark). (Panels e to h) Regression relationships between Nt contents in unrooted cuttings and their final root development at different Nd fertilization levels to donor plants (cycles = N-low, squares = N-high) (E: Total root length - TRL, F: Total root number - TRN, G: Mean length per single root – SRL, H: Unrooted cuttings – URC. (Panels a to c) Vertical bars represent 95 % confidence intervals of mean values and different lower-case letters indicate significant differences. (Panels e to h) Linear correlation coefficients: Panel e (r = 0.82), Panel f (r = 0.88), Panel g (r = 0.84) and Panel h (r = 0.89) all with n = 16, p < 0.05. Further details of experiments, rating of rooting (range per each class of root length = 1 cm), statistics and regression equations are presented in methods and with Additional file 1) Experiments of nitrogen preconditioning of cuttings, Additional file 2) Explanation of experimental designs for statistical analyses and Additional file 3) Supplemental data of figure 3 for Panel a: Exp. 7: AR-N + CYT; Panel b  Exp. 4: AR-D; Panels c and d: Exp. 2: AR-ND, and Panels e, f, g, h: Exp. 7: AR-N + CYT, respectively