Fernández-Marín Beatriz, Hernández Antonio, Garcia-Plazaola Jose I, Esteban Raquel, Míguez Fátima, Artetxe Unai, Gómez-Sagasti Maria T
Department of Plant Biology and Ecology, University of the Basque Country (UPV/EHU)Bilbao, Spain.
Front Plant Sci. 2017 Jun 19;8:1051. doi: 10.3389/fpls.2017.01051. eCollection 2017.
Despite being a small geographic extension, Mediterranean Basin is characterized by an exceptional plant biodiversity. Adaptive responses of this biocoenosis are delineated by an unusual temporal dissociation along the year between optimal temperature for growth and water availability. This fact generates the combination of two environmental stress factors: a period of summer drought, variable in length and intensity, and the occurrence of mild to cold winters. Both abiotic factors, trigger the generation of (photo)oxidative stress and plants orchestrate an arsenal of structural, physiological, biochemical, and molecular mechanisms to withstand such environmental injuries. In the last two decades an important effort has been made to characterize the adaptive morphological and ecophysiological traits behind plant survival strategies with an eye to predict how they will respond to future climatic changes. In the present work, we have compiled data from 89 studies following a meta-analytical approach with the aim of assessing the composition and plasticity of photosynthetic pigments and low-molecular-weight antioxidants (tocopherols, glutathione, and ascorbic acid) of wild Mediterranean plant species. The influence of internal plant and leaf factors on such composition together with the stress responsiveness, were also analyzed. This approach enabled to obtain data from 73 species of the Mediterranean flora, with the genus being the most frequently studied. Main highlights of present analysis are: (i) sort of photoprotective mechanisms do not differ between Mediterranean plants and other floras but they show higher plasticity indexes; (ii) α-tocopherol among the antioxidants and violaxanthin-cycle pigments show the highest responsiveness to environmental factors; (iii) both winter and drought stresses induce overnight retention of de-epoxidised violaxanthin-cycle pigments; (iv) this retention correlates with depressions of Fv/Fm; and (v) contrary to what could be expected, mature leaves showed higher accumulation of hydrophilic antioxidants than young leaves, and sclerophyllous leaves higher biochemical photoprotective demand than membranous leaves. In a global climatic change scenario, the plasticity of their photoprotective mechanisms will likely benefit Mediterranean species against oceanic ones. Nevertheless, deep research of ecoregions other than the Mediterranean Basin will be needed to fully understand photoprotection strategies of this extremely biodiverse floristic biome: the Mediterranean ecosystem.
尽管地中海盆地地域范围较小，但其植物生物多样性却极为突出。该生物群落的适应性反应表现为一年中生长的最佳温度与水分供应之间存在异常的时间分离。这一事实导致了两种环境胁迫因素的结合：时长和强度各异的夏季干旱期，以及温和至寒冷冬季的出现。这两种非生物因素都会引发（光）氧化应激，植物会精心调配一系列结构、生理、生化和分子机制来抵御此类环境伤害。在过去二十年里，人们付出了巨大努力来刻画植物生存策略背后的适应性形态和生态生理特征，以期预测它们对未来气候变化的反应。在本研究中，我们采用元分析方法收集了89项研究的数据，旨在评估野生地中海植物物种光合色素和低分子量抗氧化剂（生育酚、谷胱甘肽和抗坏血酸）的组成及可塑性。同时还分析了植物内部和叶片因素对这种组成的影响以及胁迫响应性。这种方法使我们能够获取来自地中海植物区系73个物种的数据，其中 属是研究最为频繁的。本分析的主要亮点包括：（i）地中海植物与其他植物区系的光保护机制种类并无差异，但它们表现出更高的可塑性指数；（ii）抗氧化剂中的α - 生育酚以及紫黄质循环色素对环境因素的反应最为强烈；（iii）冬季和干旱胁迫都会导致脱环氧化紫黄质循环色素在夜间滞留；（iv）这种滞留与Fv/Fm的降低相关；（v）与预期相反，成熟叶片比幼叶积累了更多的亲水性抗氧化剂，硬叶比膜质叶具有更高的生化光保护需求。在全球气候变化的背景下，其光保护机制的可塑性可能会使地中海物种比海洋物种更具优势。然而，要全面了解这个生物多样性极其丰富的植物生物群落——地中海生态系统的光保护策略，还需要对地中海盆地以外的生态区域进行深入研究。
