Decoding drought tolerance

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The health of larger organisms depends on the proper function of their circulatory or vascular systems. Human health is often compromised by cardiovascular diseases, and the same is true for plants. Plant health depends on the ability of the vascular tissue to distribute water, nutrients, and sugar across the plant body. Importantly, transport processes in plants are susceptible to environmental factors such as drought and frost. Both of these factors can trigger the formation of air embolism in xylem conduits, and this will make the supply of water to leaves more difficult. As a result of xylem blockage, leaves will reduce gas exchange, and in more severe cases this will be followed by dieback and mortality. Adverse environmental conditions are likely to also reduce sugar transport in the phloem. Drought is the main factor that compromises vascular function in plants. It is the most complex and arguably the most limiting stress factor for plant growth worldwide, in agricultural fields and forests alike. In addition, drought is often associated with fire and insect outbreaks. Despite the importance of drought in forestry and agriculture, we still lack some basic understanding of how plants cope with drought. This topic has recently received much attention among tree physiologists, as accumulating reports of drought-induced forest tree dieback have raised questions about the exact mechanism of tree dieback. The long-term goals of my research program are to understand the multiple effects of drought on vascular function and to explore how species and genotypes differ in how they cope with water shortage. The short-term objectives of my research are to: (1) Study the dynamics of whole-plant hydraulic conductance; (2) Analyze the unique cellular signatures of drought and insect defoliation in tree rings; (3) Quantify genetic variation of drought tolerance in white spruce seedlings from different climate regions; and (4) Explore how drought impacts the development and putative function of phloem. As global temperatures and precipitation regimes continue to change, there is a need for training the next generation of scientists to advance the field of drought physiology. The proposed research program will train 2 Ph.D., 2 M.Sc., and 5 undergraduate students. The knowledge gained from this research will allow us to select and eventually engineer plants with drought tolerance and growth characteristics that will match current and future challenges in their growing environment.