Impact of hydraulic architecture on tree performance

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Dr. Tyree has developed quantitative models that predict how hydraulic conductivity of trees impacts the photosynthetic process and hence the rate of tree growth. But more discovery oriented research needs to be done to validate and improve the predictive capacity of the model.There is increasing evidence that the efficiency of water transport (hydraulic conductance) in soils and in roots, stems and leaves of trees sets limits on tree performance: transpiration, carbon gain and growth-rate of trees. Furthermore, there is evidence of a strong negative-impact of drought events and freeze-thaw cycles on the efficiency of water transport and hence tree productivity and survival. More recently, it has become clear that plants have dynamic control over root and leaf hydraulic conductance through gene expression for aquaporins, which are proteins that reside in cell membranes and which enhance water transport in trees.The purpose of the research program in this NSERC Discovery Grant is to critically analyze hydraulic architecture of Canada's most widespread trees, poplars, aspens and cottonwoods. The studies will investigate root and shoot components of water transport, including xylem structure and function and aquaporins, with particular emphasis on prospective adaptations to drought and cold. These water relations characteristics will be compared with those of tropical trees that are being investigated in ongoing studies. The research will reveal fundamental aspects of tree ecophysiology and adaptation to cold-temperate climates, and address the broader question, 'how are trees uniquely adapted to different biophysical ecoregions?'.A secondary intent is to transfer the knowledge base gained to potential commercial exploitation in sustainable forestry practices and agro-forestry