title: The impact of vessel size on vulnerability curves: data and models for within-species variability in saplings of aspen, Populus tremuloides Michx.
abstract: The objective of this study was to quantify the relationship between vulnerability to cavitation and vessel diameter within a species. We measured vulnerability curves (VCs: percentage loss hydraulic conductivity versus tension) in aspen stems and measured vessel-size distributions. Measurements were done on seed-grown, 4-month-old aspen (Populus tremuloides Michx) grown in a greenhouse. VCs of stem segments were measured using a centrifuge technique and by a staining technique that allowed a VC to be constructed based on vessel diameter size-classes (D). Vessel-based VCs were also fitted to Weibull cumulative distribution functions (CDF), which provided best-fit values of Weibull CDF constants (c and b) and P(50) = the tension causing 50% loss of hydraulic conductivity. We show that P(50) = 6.166D(-0.3134) (R(2) = 0.995) and that b and 1/c are both linear functions of D with R(2) > 0.95. The results are discussed in terms of models of VCs based on vessel D size-classes and in terms of concepts such as the 'pit area hypothesis' and vessel pathway redundancy.
authors.affiliation: College of Forestry, Northwest A&F University, Yangling, Shaanxi, 712100, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Cai
authors.forename: Melvin T
authors.initials: MT
authors.lastname: Tyree
mesh_terms: D008954:Models, Biological; D018547:Plant Stems / Q000033:anatomy & histology / Q000502:physiology*; D032107:Populus / Q000033:anatomy & histology / Q000502:physiology*; D014867:Water / Q000502:physiology*
chemical_list: D014867:Water