Photoprotective Strategies of Mediterranean Plants in Relation to Morphological Traits and Natural Environmental Pressure: A Meta-Analytical Approach

Abstract

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 Quercus 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.

How do vascular plants perform photosynthesis in extreme environments? An integrative ecophysiological and biochemical story

“…The reported values for the VAZ pool range from 60–70 mmol mol −1 Chl a+b in alpine R. glacialis and desert Atriplex halimus (Streb et al , , ) to 110–160 mmol mol −1 Chl a+b in species such as Polylepis tarapacana from a high elevation in the Andes, the Antarctic C. quitensis and the Arctic Salix pulchra (Bascuñán‐Godoy et al , ; García‐Plazaola et al , ; Magney et al , ). These values are within the normal range of VAZ pool sizes described for vascular plants (roughly from 20 to 180 mmol mol −1 Chl a+b in non‐stressed plants; Esteban et al , ; Fernández‐Marín et al , ).…”

Born to revive: molecular and physiological mechanisms of double tolerance in a paleotropical and resurrection plant

“…2) but within an expected range for a shade-preferring species (S arv ari et al, 2014;Esteban et al, 2015;Georgieva et al, 2017b;Fern andez-Mar ın et al, 2018a). The VAZ pool and the Toc : Chl ratios were moderately high and comparable to values of Mediterranean herbaceous species (Munn e-Bosch et al, 2016;Fern andez-Mar ın et al, 2017). The thylakoid ratio of MGDG : DGDG was rather low (Fig.…”

First evidence of freezing tolerance in a resurrection plant: insights into molecular mobility and zeaxanthin synthesis in the dark

“…The risk of exacerbated oxidative pressure occurs as a consequence of the limitation of the photosynthetic activity specifically, and of the metabolism in general, due to dramatically slowed molecular mobility (cell vitrification) (Verhoeven et al ). Under these circumstances, photoprotective mechanisms are upregulated, either to dissipate excess absorbed light energy as heat or to protect cellular integrity from damaging oxidative reactions, which is essential for the survival of the photosynthetic tissue (Öquist and Huner , Adams et al , Chaves et al , Verhoeven , Fernández‐Marín et al ). Different ecophysiological strategies have evolved in plants to survive frost.…”