Fig. 5. Quantification of average axonal stop zones in different gradients. (A,B) The two graphs show the averaged axonal growth curves for five gradients printed with 8 µg/ml (A) or 4 µg/ml (B). The relative slope of the gradients is indicated with the colour code given in A. In A, the averaged curve of Fc controls is shown in black, the curve of nasal controls in gray and the arithmetic mean of the axonal fluorescence in pink. For both ephrin concentrations axonal curves intersect the arithmetic average later the shallower the gradient is. Curves in B intersect the arithmetic mean later than curves in A. The axonal curves were averaged from n=7 (gradient slope 1/6), n=8 (1/3), n=9 (1/2), n=5 (2/3), n=6 (1), n=10 (Fc controls), n=5 (nasal controls) experiments in A, and from n=9 (1/6), n=9 (1/3), n=8 (1/2), n=13 (2/3), n=7 (1) experiments in B. Mean stop point positions are 64.9±4.2 µm (1/6), 58.3±3.9 µm (1/3), 51.2±3.1 µm (1/2), 40.2±3.6 µm (2/3), 24.4±2.2 µm (1) in A and 97.9±6.8 µm (1/6), 86.8±7.3 µm (1/3), 80.3±8.0 µm (1/2), 73.8±5.1 µm (2/3), 52.3±5.5 µm (1) in B. (C) Plotting the stop point positions determined in A and B and stop point positions in gradients printed with 2 µg/ml against the relative slope of the corresponding gradients shows that the two parameters correlate in a linear way. Error bars indicate the standard error. Mean stop positions in gradients printed with 2 µg/ml are: 178.8 µm (1/6, n=4), 169.6±8.5 µm (1/3, n=5), 152.0±10.2 µm (1/2, n=5), 145.5±12.4 µm (2/3, n=5), 110.3±17.5 µm (1, n=5). Due to the data examination method, no standard error could be calculated for the mean stop point position in the gradient with the slope 1/6 (marked with a star, for details see Materials and methods). P<0.002 by ANOVA for both of the two groups of 8 µg/ml and 4 µg/ml gradients and P<0.156 for 2 µg/ml gradients. Studens t-test was applied to compare the mean stop points in gradients with the same slope but printed with 8 µg/ml and 4 µg/ml: P<0.002 (gradient slope 1/6), P<0.006 (1/3), P<0.003 (1/2), P<0.001 (2/3), P<0.002 (1).