Fig. 4

Estimation of CA velocity in individual bundles. A The monitoring of individual vascular bundle at the lowest slice over the entire experiment (upper panel). Simultaneous monitoring of the same vascular bundle at the highest slice (low panel). The distance between the lowest and highest slice was 1.1 cm. The temporal delay of the CA arrival at highest slice is clearly distinguishable (arrowed). This is exploited to calculate the vertical transport velocities of the CA along the vascular bundles. B–D Analogous monitoring data are shown for other bundles (b, c and d, as pictured in Fig. 3B). E The velocity value as estimated using monitoring data