Torus-margo pits cannot function in vessel-bearing angiosperms

The evolution of plant hydraulics reflects a trade-off between efficiency and safety, between maximizing water transport while preventing embolism spread. Two major lineages achieved this balance differently: conifers and Gingko optimized safety through low resistance torus-margo pits, while angiosperms maximized hydraulic efficiency through long, wide vessels. It is therefore striking that no lineage evolved a “hybrid” design combining the efficiency of vessels with the low resistance of margo membranes with potential exception of Ephedraceae. Here we use a combination of experimental and theoretical approaches to show that the geometry of vessels inherently limits the pressure differentials required for torus-margo function.