title: Drought-induced xylem pit membrane damage in aspen and balsam poplar.
abstract: Drought induces an increase in a tree's vulnerability to a loss of its hydraulic conductivity in many tree species, including two common in western Canada, trembling aspen (Populus tremuloides) and balsam poplar (Populus balsamifera). Termed 'cavitation fatigue' or 'air-seeding fatigue', the mechanism of this phenomenon is not well understood, but hypothesized to be a result of damage to xylem pit membranes. To examine the validity of this hypothesis, the effect of drought on the porosity of pit membranes in aspen and balsam poplar was investigated. Controlled drought and bench dehydration treatments were used to induce fatigue and scanning electron microscopy (SEM) was used to image pit membranes for relative porosity evaluations from air-dried samples after ethanol dehydration. A significant increase in the diameter of the largest pore was found in the drought and dehydration treatments of aspen, while an increase in the percentage of porous pit membranes was found in the dehydration treatments of both species. Additionally, the location of the largest pore per pit membrane was observed to tend toward the periphery of the membrane.
authors.affiliation: University of Alberta, Department of Renewable Resources, 442 ESB, Edmonton, AB, T6G 2E3, Canada. hillabra@ualberta.ca.
authors.forename: Rachel M
authors.initials: RM
authors.lastname: Hillabrand
authors.affiliation: University of Alberta, Department of Renewable Resources, 442 ESB, Edmonton, AB, T6G 2E3, Canada.
authors.forename: Uwe G
authors.initials: UG
authors.lastname: Hacke
authors.affiliation: University of Alberta, Department of Renewable Resources, 442 ESB, Edmonton, AB, T6G 2E3, Canada.
authors.forename: Victor J
authors.initials: VJ
authors.lastname: Lieffers
mesh_terms: D001692:Biological Transport; D003681:Dehydration; D057446:Hydrodynamics; D032107:Populus / Q000378:metabolism* / Q000648:ultrastructure; D014867:Water / Q000378:metabolism*; D052584:Xylem / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D014867:Water
keywords: bordered pits; cavitation fatigue; drought; electron microscopy