Interactions of plants with the environment: optimization of phytoremediation and mechanisms of phytotoxicity of contaminating chemicals

植物暴露于环境污染物，如多环芳烃（PAH），石油烃（PHC），金属和盐。这些污染物对植物是有毒的，并且许多通过活性氧（ROS）起作用。基于毒性机制，缓解胁迫的策略可用于改善植物修复。两个正在进行的项目是植物修复的优化和植物毒性的机制。 优化植物修复：由于污染物的持久性，往往需要修复。植物修复有很大的希望，因为植物根系可以提供大量的汇污染物的分区出土壤。植物修复面临着许多障碍，其中突出的是污染物的植物毒性。基于我们的毒理学工作，我们已经制定了策略，以实现对污染物的耐受性-一个关键方面是植物生长促进根际细菌（PGPR）。这促使我们开发了PGPR增强植物修复系统（PEPS），该系统可加速植物生长并修复受污染的土壤。对于PHC和PAH，植物支持土壤中的微生物群落，微生物代谢PHC和PAH。对于盐，离子被吸收到树叶中，并且可以沿着树叶从现场移除。目前正在实验室和实地优化植物修复，以进行PHC和盐修复。为了使PEPS更有效，我们需要更好地了解植物修复过程中植物胁迫和驯化的机制。为了实现这一目标，我们将通过研究光合作用，类黄酮，活性氧清除和基因表达来研究草和谷物在植物修复过程中的表现。我们还将研究使用过氧化钙和乳化剂增强植物修复PHC。前者将增加土壤中污染物代谢所需的O2水平，后者将使PHC更具生物有效性。 环境污染物的植物毒性机制：我们已经表明，多环芳烃和PHC是植物毒性和紫外线辐射增强其毒性。在许多情况下，损伤是通过ROS对光合机构的。此外，我们发现金属通过ROS机制协同PAH和PHC毒性。我们还发现，PHC，PAH，金属和盐激活许多相同的驯化过程通过ROS信号。为了更好地了解植物毒性的机制，我们将通过研究光合作用，类黄酮，ROS清除酶和基因表达的变化来研究PHC，PAH，盐和金属对油菜，草和谷物的影响。我们最近发现，在土壤的植物修复过程中，但在达到预期的无毒水平之前，土壤中的污染物变得无毒。我们将研究土壤中污染物毒性损失的机制基础，这应该指向污染物植物毒性的关键机制。

Plants are exposed to environmental contaminants such as polycyclic aromatic hydrocarbons (PAH), petroleum hydrocarbons (PHC), metals and salt. These contaminants are toxic to plants, and many act via reactive oxygen species (ROS). Based on toxicity mechanisms, strategies for stress alleviation can be used to improve phytoremediation. Two on-going projects are optimization of phytoremediation and mechanisms of phytotoxicity. Optimization of Phytoremediation: Due to persistence of contaminants, remediation is often required. Phytoremediation holds great promise because plant roots can provide large sinks for partitioning of contaminants out of soil. Phytoremediation has faced many obstacles; prominent among these is phytotoxicity of the contaminants. Based on our toxicology work, we have developed strategies to achieve tolerance to contaminants - a key aspect is plant growth with plant growth promoting rhizobacteria (PGPR). This led us to develop PGPR-Enhanced Phytoremediation Systems (PEPS), which show accelerated plant growth and remediation in contaminated soils. For PHC and PAH, plants support microbial communities in the soil and the microbes metabolize the PHC and PAH. For salt, the ions are taken up into foliage and can be removed from the site along with the foliage. Phytoremediation is being optimized at the laboratory and field levels for PHC and salt remediation. To make PEPS more effective, we need to better understand the mechanisms of plant stress and acclimation during phytoremediation. To achieve this we will study the performance of grasses and cereals during phytoremediation by examining photosynthesis, flavonoids, ROS scavenging and gene expression. We will also examine enhancement of phytoremediation of PHC using calcium peroxide and emulsifiers. The former will increase soil O2 levels for contaminant metabolism and the latter will render the PHC more bioavailable. Mechanisms of phytotoxicity of environmental contaminants: We have shown that PAH and PHC are phytotoxic and their toxicity is enhanced by UV radiation. In many instances, damage is to the photosynthetic apparatus via ROS. Further, we have found that metals synergize PAH and PHC toxicity via ROS mechanisms. We have also found that PHC, PAH, metals and salt activate many of the same acclimation processes via ROS signalling. To better understand mechanisms of phytotoxicity, we will examine the effects of PHC, PAH, salt and metals on Brassica napus, grasses and cereals by examining changes to photosynthesis, flavonoids, ROS scavenging enzymes and gene expression. We have recently found that during phytoremediation of soils, but prior to reaching predicted non-toxic levels, the contaminants in the soil become non-toxic. We will examine the mechanistic bases for loss of toxicity of the contaminants in the soil, which should point to the key mechanisms of contaminant phytotoxicity.