Results
Using the optical method, we were able to observe clear embolism events in xylem during dehydration. In most of the species observed these embolism events began once plants were dehydrated to at least -1 MPa and accumulated as Ψ declined (Figure 1). When rehydrated, Ψ recovered within 60 minutes to high values similar to those observed in the hydrated stems at the start of the experiment. However, differences were observed in the cessation of embolism formation upon rehydration across the species observed. In the angiosperm I. verticillatarehydrated just after 50% of the xylem had embolized, very little (1.7%, Figure 1A) embolism was observed immediately after rehydration. Yet in the conifer A. robusta , also rehydrated just after 50% of the xylem had embolized, considerable embolism (10.3 %, Figure 1B) occurred as Ψ was relaxing (Figure 1B). In no sample did we observe refilling of embolized conduits after stem rehydration.