Importance of the antioxidant capacity of phenolic metabolites in plant resistance against oxidative stress

我们以前的研究结果表明，酚类代谢物（PHENs）存在于叶片中，通过其对紫外诱导荧光的影响，代表内部探针，可以揭示植物生长和光合作用之间的不平衡。除了对荧光的影响外，PHENs还具有抗氧化特性，可能在植物中对氧化胁迫起保护作用。这项研究计划的长期目标是诱导PHENs的积累，以保护植物免受氧化胁迫，从而提高其生产力和食品质量。这项研究计划的全球方法将首先改善我们对直接在叶子中（植物中）的PHEN抗氧化活性的估计，然后测试生长调节剂和培养实践是否可以以最小的代谢成本提高PHEN浓度和抗氧化活性，最后证明如果增加叶子中的PHEN浓度，则会导致对过量光和重金属引起的氧化胁迫的更高抗性。更具体地说，我们将首先定义一个指数的PHEN抗氧化剂活性在植物的基础上测量的一组参数从几个（作物，芳香族和药用）物种的叶子，特别是使用循环伏安法来评估可氧化化合物的浓度和它们的氧化还原电位。在第二阶段，用矮向日葵（“Sunspot”）植物进行的实验将证明通过生长调节剂（水杨酸、Actigard®、茉莉酸）和栽培实践（短期氮缺乏或根缺氧）诱导PHEN积累如何能够以最小的代谢成本增强PHEN抗氧化能力。最后，我们将测试具有增加的PHEN浓度、增强的抗氧化能力并且理想地没有氧化损伤迹象（正常生长和光合作用）的“活化”植物是否比正常植物更能抵抗由光抑制（过度光强度）或铜引起的氧化应激。

Our previous results demonstrated that phenolic metabolites (PHENs) present in leaves, by their effects on UV-induced fluorescence, represent internal probes that can reveal imbalances between plant growth and photosynthesis. Besides their effects on fluorescence, PHENs have antioxidant properties that may play a protecting role against oxidative stress in plants. The long term objective of this research program is to induce the accumulation of PHENs in order to protect plants against oxidative stress that may enhance their productivity and food quality. The global approach of this research program will be first to improve our estimations of PHEN antioxidant activities directly in leaves (in planta), then test if growth regulators and cultural practices could enhance PHEN concentrations and antioxidant activities with minimal metabolic costs, and finally demonstrate if increased PHEN concentrations in leaves result in higher resistance against oxidative stress caused by excess light and heavy metals. More specifically, we will first define an index of PHEN antioxidant activities in planta based on a set of parameters measured in leaves from several (crop, aromatic and medicinal) species, using notably cyclic voltammetry to assess the concentration of oxidisable compounds and their redox potential. In the 2nd phase, experiments with dwarf sunflower ("Sunspot") plants will demonstrate how the induction of PHEN accumulations by growth regulators (salicylic acid, Actigard®, jasmonic acid) and cultural practices (short term nitrogen deficiency or root hypoxia) can enhance PHEN antioxidant capacities and this, at minimal metabolic costs. Finally, we will test if "activated" plants that have increased PHEN concentrations, enhanced antioxidant capacities, and ideally, no sign of oxidative damages (normal growth and photosynthesis) are more resistant than normal plants against oxidative stress caused by photoinhibition (excess of light intensity) or copper.