PARENT SESSION
Poster Session #40: Water Relations I.
Wednesday, August 7. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Water transport, conduit size variation and cascading cavitation in Pinus albicaulis: Results from a model.

Sonderegger, Derek^*,1, Taper, Mark¹, ¹ Montana State University, Bozeman, Montana

ABSTRACT- Details of plant hydraulic architecture such as conduit length and radius have profound impacts on the species' ecology and life history including species' range and response to global climate change. Species with the propensity to display strip-bark morphology, which is characterized by partial cambial mortality, offer a unique system to study the impact of hydraulic architecture on tree physiological ecology and subsequent responses to changes in environmental conditions. We hypothesized that the mechanism generating strip-bark morphology may be a cascading cavitation event that is contained within confined hydraulic sectors. We built a computer simulation to examine whether this mechanism can explain the observed morphology. We assumed that the probability that a particular conduit cavitates (POC) was based on both its water potential and architecture (length and radius). A tree with uniform architecture will have POCs increase monotonically with water potentials, and thus cannot yield a cascading cavitation event, since a cavitation event should occur at the top and the spread (if any) would be upward. Water transport in xeric environments should be maximized under typical environmental conditions when the POC is constant along the water path. Thus the architectural contribution must decline with height offsetting the water potential gradient. If a conduit having previously cavitated affects the POC of a neighboring conduit, then the cavitation of one conduit could easily trigger a cascading cavitation event, especially when water potentials are maximized for typical conditions.

KEY WORDS: water transport, xylem, cavitation, model