Interactions of plants with the environment: impacts of contaminants on plants and phytoremediation of contaminants

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Plants are exposed to numerous environmental stressors including contaminants such as polycyclic aromatic hydrocarbons (PAHs), petroleum hydrocarbons (PHCs), metals, salt and pesticides. Most of these contaminants are toxic to plants at environmentally relevant concentrations, and many act through reactive oxygen species (ROS). When the mechanisms of toxicity are understood, a strategy to alleviate stress can be established, improving the chances that plants can be used for soil remediation (phytoremediation). Two ongoing projects in my research program pertain to how plants interact with contaminants. 1) Mechanisms of Phytotoxicity: We have shown that PAHs, oxyPAHs, PHCs, metals and salt are phytotoxic. These compounds impact on photosynthesis, often via ROS mechanisms. To better understand mechanisms of phytotoxicity, we will examine the effects of PAHs and metals on photosynthesis in Brassica, Lemna and Arabidopsis. We also found that PAHs, metals and UVB activate many of the same acclimation processes via ROS and redox signaling pathways. Thus, we will examine acclimation via accumulation of ROS scavenging enzymes and flavonoids, as well as ROS and redox induced gene expression. 2) Optimization of Phytoremediation: To remediate persistent contaminants from industrial sites (e.g., brownfields and oil wells), development of effective and environmentally responsible remediation technologies such as phytoremediation are crucial. Although plant roots can remove contaminants from soil, these contaminants often cause plant stress, impeding growth. Based on our toxicology work above, we can refine existing phytoremediation strategies to improve plant tolerance in impacted soils. The key to the systems we are developing is the alleviation of plant stress with plant growth promoting rhizobacteria. To make these systems more effective we need to better understand the mechanisms of plant stress and acclimation during phytoremediation. To do this we will study the performance of grass species and cereals during phytoremediation of PHC and salt using photosynthesis, flavonoid composition, ROS scavenging capacity and gene expression as measures of acclimation and stress.