Figure 4.

Parameterization of the Velocity Profile

(A) The parameter Trx is found as the x-coordinate of the intersection of the two best-fitted regression lines (red) to the raw data (black, velocity profile) for a single time point.

(B) The slopes m1 and m2 are found by centering a 300-μm window at Trx and then fitting lines to the data on either side (red). Finally, x-int is found from the x coordinate of the intersection of the velocity profile with a reference velocity (horizontal blue dotted line). The reference is obtained for a given root as the y coordinate of the midpoint of the average regression interval used to find m2.

(C) Parameter time courses.

Parameters for each root were averaged over time, expressed as a percentage of the mean, and then translated horizontally so that each curve would start at 100. The tip velocity parameter is measured directly by Stripflow along with the velocity profile. The time course for m1 is omitted for clarity. Sample size = 35. Parameters (including m1) are plotted as absolute values in Figures S10 and S11.