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中，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，许多是通过活性氧（ROS）起作用的。基于毒性机制，可以采用缓解胁迫的策略来改善植物修复。两个正在进行的项目是植物修复的优化和植物毒性机制。***植物修复的优化：由于污染物的持久性，通常需要修复。植物修复具有很大的前景，因为植物根系可以为土壤中的污染物提供大量的吸收池。植物修复面临许多障碍；其中最突出的是污染物的植物毒性。基于我们的毒理学工作，我们制定了实现污染物耐受性的策略-一个关键方面是植物生长与植物生长促进根瘤菌（PGPR）。这促使我们开发了pgpr增强植物修复系统（PEPS），该系统显示了污染土壤中植物生长和修复的加速。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，离子被吸收到叶子中，并可以随叶子一起从该部位移除。在实验室和实地两级，植物修复正在优化，以修复PHC和盐。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。我们还将研究过氧化钙和乳化剂对PHC植物修复的增强作用。前者将增加土壤中用于污染物代谢的氧含量，后者将使PHC更具生物可利用性。***环境污染物的植物毒性机制：我们已经证明多环芳烃和PHC具有植物毒性，并且它们的毒性在紫外线照射下增强。在许多情况下，损害是通过活性氧对光合机构造成的。此外，我们发现金属通过ROS机制协同多环芳烃和PHC毒性。我们还发现，PHC、PAH、金属和盐通过ROS信号激活了许多相同的驯化过程。为了更好地了解植物毒性机制，我们将通过检测光合作用、类黄酮、ROS清除酶和基因表达的变化来研究PHC、PAH、盐和金属对甘蓝型油菜、禾草和谷物的影响。我们最近发现，在土壤的植物修复过程中，但在达到预测的无毒水平之前，土壤中的污染物变得无毒。我们将研究土壤中污染物毒性丧失的机制基础，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.