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

我们之前的研究结果表明，酚代谢物（PHENs）存在于叶片中，通过它们对紫外线诱导的荧光的影响，代表了可以揭示植物生长和光合作用之间不平衡的内部探针。除了对荧光的影响外，PHENs还具有抗氧化特性，可能对植物的氧化应激起保护作用。本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应激，从而提高其生产力和食品质量。该研究计划的全球方法将首先改进我们对植物叶片中PHEN抗氧化活性的估计，然后测试生长调节剂和培养方法是否可以在最小的代谢成本下提高PHEN浓度和抗氧化活性，最后证明叶片中PHEN浓度的增加是否能提高对过量轻重金属引起的氧化应激的抵抗力。更具体地说，我们将首先根据几种（作物、芳香和药用）物种叶片中测量的一组参数定义植物中PHEN抗氧化活性指数，特别是使用循环伏安法来评估可氧化化合物的浓度及其氧化还原电位。在第二阶段，以矮小向日葵（“太阳黑子”）植物为实验对象，将展示生长调节剂（水杨酸、Actigard®、茉莉酸）和培养措施（短期缺氮或根部缺氧）如何诱导PHEN积累，并以最小的代谢成本提高PHEN的抗氧化能力。最后，我们将测试那些PHEN浓度增加、抗氧化能力增强、理想情况下没有氧化损伤迹象（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（光强过剩）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.