The significance of pit shape for hydraulic isolation of embolized conduits of vascular plants during novel refilling.

During plant water transport, the water in the conducting tissue (xylem) is under tension. The system is then in a metastable state and prone to bubble development and subsequent embolism blocking further water transport. It has recently been demonstrated, that embolism can be repaired under tension (= novel refilling). A model (Pit Valve Mechanism = PVM) has also been suggested which is based on the development of a special meniscus in the pores (pits) between adjacent conduits. This meniscus is expected to be able to isolate embolized conduits from neighbouring conduits during embolism repair. In this contribution the stability of this isolating meniscus against perturbations is considered which inevitably occur in natural environments. It can be shown that pit shape affects the stability of PVM fundamentally in the case of perturbation. The results show that a concave pit shape significantly supports the stability of PVM. Concave pit shape should thus be of selective value for species practicing novel refilling.