Vein progression with Vascular Attraction Factor.

Simulation performed on the same tissue template as in Fig 5, with the same spatial distribution of auxin production and turnover, and same color code. The only additional ingredient is the production of a Vascular Attraction Factor (VAF), produced by sink cells and biasing vein progression towards higher concentration of VAF. As a result, all veins eventually connect to a sink. (A) The tissue is viewed obliquely from the bottom. (B) Longitudinal cutaway with two veins (arrows indicate correspondence with panel A. (C) Longitudinal cutaway with the third vein. Note that auxin has no longer time to accumulate in the vein portions near sinks, since connection to sink occurs very early.