Abstract Detail

Ecophysiology

Hillabrand, Rachel [1], Hacke, Uwe G. [2].

Investigating the mechanisms of cavitation fatigue in two tree species of western Canada.

Tree-dieback in western Canada due to drought has been extensive in recent years. Predictions of a drier climate in the next decades have increased interest in the mechanisms of tree mortality following water stress. Cavitation fatigue is a phenomenon whereby trees previously subject to drought have an increased vulnerability to a loss of their hydraulic conductivity, possibly due to irreparable damage to the xylem. Hydraulic conductivity is lost by the cavitation of xylem vessels and, according to the air-seeding hypothesis, spread by air bubbles entering into adjacent conduits through pores in the pit membranes. A greenhouse experiment was conducted to test the hypothesis that trees which experience drought have a greater incidence of pit membranes with large pores, and thus, lower air-seeding pressures. Two species were included in the study, aspen (Populus tremuloides) and balsam poplar (Populus balsamifera), which are common in western Canada and known to experience cavitation fatigue. Pit membranes of control and drought-stressed trees were observed with scanning electron microscopy and the diameter of the largest pore per membrane was measured to calculate its air-seeding pressure. To hypothesize why pores may be larger in drought-stressed trees, an additional experiment was performed. The xylem sap of aspen trees was collected and analyzed for changes in its chemical properties due to drought stress.

1 - University of Alberta, Renewable Resources , University of Alberta , 442 Earth Sciences Building, Edmonton , AB, AB T6G 2E3, Canada
2 - University of Alberta, Renewable Resources, Edmonton, AB, T6G 2E3, Canada

Keywords:
Aspen
climate change
plant hydraulics
cavitation fatigue
pit membranes
xylem
drought.

Presentation Type: Oral Paper:Papers for Topics
Session: 25
Location: Salon 16/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 8:30 AM
Number: 25003
Abstract ID:311
Candidate for Awards:Physiological Section Physiological Section Li-COR Prize