Looping Network Meetings

#74 November 17, 2025

Monday 15:00 (Paris/Warsaw time)

Przemysław Prusinkiewicz (University of Calgary)

Morphogenesis of closed-loop vascular patterns in Pilea leaves

Abstract:
Despite their ubiquity in nature and accessibility for study, reticulate (closed-loop) leaf venation patterns remain poorly understood. The dominant conceptual and computational model is based on the Sachs’ canalization hypothesis, which attributes vein patterning to positive feedback between the plant hormone auxin and its transporters. Canalization plausibly explains the emergence of branching patterns connecting auxin sources to sinks, but not the formation of loops.

In my presentation, I will focus on the herbaceous plant Pilea peperomioides, for which progress has recently been made. While leaves of most plants have hydathodes (water-secreting pores) restricted to the leaf margin, in Pilea they are distributed across the entire leaf blade. Unexpectedly, we found that the main veins of Pilea leaves approximate Voronoi polygons surrounding these hydathodes.

To explain this pattern, we hypothesized that it is generated by colliding waves of auxin concentration propagating outward from the hydathodes. Although fundamentally different from canalization, the colliding-wave model is consistent with a previously postulated model of auxin transport by active transporters, as well as with molecular data we acquired for model validation.

These results have been obtained in collaboration with Xingyu Zheng, Shirsa Palit and Saket Navlakha (Cold Spring Harbor Laboratory, NY), and Enrico Scarpella (University of Alberta, AB, Canada).

Recording