Differences in drought avoidance rather than differences in the fast versus slow growth spectrum explain distributions of two Asclepias species.

Understanding factors that determine a species' geographical range is crucial for predicting climate-induced range shifts. Two milkweed species, Asclepias syriaca and Asclepias speciosa, have overlapping ranges along a moisture gradient in North America and are primary food sources for endangered monarch caterpillars. With decreasing moisture, long-lived species often exhibit slower growth and greater drought tolerance, while many annual species exhibit faster growth strategies.

Evolutionary constraint on low elevation range expansion: Defense-abiotic stress-tolerance trade-off in crosses of the ecological model .

Most transplant experiments across species geographic range boundaries indicate that adaptation to stressful environments outside the range is often constrained. However, the mechanisms of these constraints remain poorly understood. We used extended generation crosses from diverged high and low elevation populations.

Does acclimation in cavitation resistance due to mechanical perturbation support the pit area or conduit reinforcement hypotheses in Phaseolus vulgaris?

Two Phaseolus vulgaris L. cultivars were exposed to reduced water and stem mechanical perturbation treatments (flexing) to determine if acclimation to these treatments induced hydraulic changes, altered cavitation resistance and changed stem mechanical properties. Additionally, this study sought to determine if changes in cavitation resistance would support the pit area or conduit reinforcement hypotheses.

Effect of Drought on Herbivore-Induced Plant Gene Expression: Population Comparison for Range Limit Inferences.

Low elevation "trailing edge" range margin populations typically face increases in both abiotic and biotic stressors that may contribute to range limit development. We hypothesize that selection may act on ABA and JA signaling pathways for more stable expression needed for range expansion, but that antagonistic crosstalk prevents their simultaneous co-option. To test this hypothesis, we compared high and low elevation populations of Boechera stricta that have diverged with respect to constitutive levels of glucosinolate defenses and root:shoot ratios; neither population has high levels of both traits.

Constraints to hydraulic acclimation under reduced light in two contrasting Phaseolus vulgaris cultivars.

Two cultivars of Phaseolus vulgaris L. were grown under three light levels to determine if hydraulic acclimation to light occurs in herbaceous annuals and whether intraspecific trade-offs constrain hydraulic traits. Acclimation occurred in response to reduced light and included decreased stomatal density (SD) and increased specific leaf area (SLA).

Drought-induced trans-generational tradeoff between stress tolerance and defence: consequences for range limits?

Areas just across species range boundaries are often stressful, but even with ample genetic variation within and among range-margin populations, adaptation towards stress tolerance across range boundaries often does not occur. Adaptive trans-generational plasticity should allow organisms to circumvent these problems for temporary range expansion; however, range boundaries often persist. To investigate this dilemma, we drought stressed a parent generation of Boechera stricta (A.

Long-term acclimatization of hydraulic properties, xylem conduit size, wall strength and cavitation resistance in Phaseolus vulgaris in response to different environmental effects.

Phaseolus vulgaris grown under various environmental conditions was used to assess long-term acclimatization of xylem structural characteristics and hydraulic properties. Conduit diameter tended to be reduced and 'wood' density (of 'woody' stems) increased under low moisture ('dry'), increased soil porosity ('porous soil') and low phosphorus ('low P') treatments. Dry and low P had the largest percentage of small vessels.

Patterns of tree dieback in Queensland, Australia: the importance of drought stress and the role of resistance to cavitation.

During the extreme 1992-1997 El Niño drought event, widespread stem mortality, or tree "dieback", of both mature and juvenile eucalypts occurred within the tropical savannas of northeast Australia. Most of the dieback occurred in individuals of the ironbark species complex ( Eucalyptus crebra- E. xanthoclada) while individuals of the bloodwood species Corymbia erythrophloia, exhibited significantly less stem mortality.

Patterns of stomatal conductance among blue oak (Quercus douglasii) size classes and populations: implications for seedling establishment.

Quercus douglasii Hook. & Arn. (blue oak) is a deciduous white oak that is currently failing to regenerate throughout much of its range in California, USA.