Ecophysiology of environmental contaminants in plants

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Plants face a number of environmental stresses. My lab primarily studies cadmium stress. Cadmium is soluble in water, readily taken up by plants and toxic to humans in small doses. Soils normally contain low cadmium. Higher concentrations can arise due to industrial activity, burning fuel or long-term use of fertilizers that contain trace amounts of this metal. Amounts of cadmium in the edible parts of some Canadian crops can approach or exceed the limits for safe consumption. There is, therefore, a pressing need to understand the factors that control cadmium uptake, movement and storage in plants. Our scientific approach is three-pronged. The first type of experiment tests the biological and chemical factors that make cadmium more, or less, available for plant uptake. The second type of study examines the fate of cadmium in plant tissues. Knowing where, and to what, the cadmium is bound provides information about how cadmium is detoxified and stored within the plant. These experiments will also reveal the route that cadmium takes on its way from roots to shoots. This information will be used to build mathematical models of metal and nutrient movement in plants. These models can be used to predict what will happen to plants if the conditions change. The data from uptake and movement studies can also be used to set limits for metals in soil and ensure safety of Canadian food crops. For the third type of approach, we study the physiology and genetics of the plant response to metal-stress. This includes the response of certain enzymes and pathways that are involved in 1) producing molecules that can bind, detoxify and store cadmium or 2) reducing plant stress. By comparing plants that lack, or over-express, these enzymes and responses we can learn more about how plants respond to metals. A new direction of research in my lab is the study of a recently identified type of contaminant, called benzalkonium chlorides (BACs). This class of chemicals is used in most cleaning products. BACs are found in wastewater and in sewage sludge. Crops can be exposed to BACs by irrigation or by adding sludge as a fertilizer. My lab will determine the extent to which they are harmful to plants. We will also learn how they are taken up by plants. The results of my research have broad applications. For example, features of plants that increase metal uptake can be used to select plants that help clean contaminated soil. On the other hand, features of plants that reduce metal uptake can be selected to improve food safety. The data we collect can also be used to improve environmental laws. For example, we can recommend legal limits for contaminants in farm soil.