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Adenanthera pavonina is a medicinal species, which economic value depends on the richness of its phytocompounds. Extreme climatic conditions are becoming frequent worldwide, but despite their impact on plant productivity these weather events also modulate plants' metabolism increasing the production of important phytocompounds. We aimed to characterize the physiological and metabolite adjustments in A. pavonina leaves induced by drought and UV-B radiation. Plants were exposed to drought (DS), UV-B radiation (UV-B), and drought + UV-B (DS + UV-B), and photosynthesis, lipophilic metabolites, and antioxidant status were evaluated. The stress conditions compromised the photosynthetic performance and induced oxidative stress (DS and UV-B plants). However, plants activated protective mechanisms (increased antioxidant activity and flavonoids in all treatments, total phenols in DS and DS + UV-B, and catechols in UV-B and DS + UV-B) and modulated their lipophilic profiles (accumulation of fatty acids and TCA cycle-related metabolites, and reduction of carbohydrates) to cope with the stress. We demonstrate for the first time that DS and UV-B radiation can enrich A. pavonina leaves with antioxidants and fatty acids increasing their medicinal value. [ABSTRACT FROM AUTHOR]

Cork oak (Quercus suber), native to Mediterranean areas, is a plant of ecological and economical relevance, nevertheless, the effects of soil salinization on this species are currently unknown. We have investigated the physiological and biochemical impact of a high-salinity episode on young cork oak (Q. suber) plants. Besides the control (plants only irrigated with water), two experimental groups (irrigated once with a 300 mM NaCl solution) were analysed, one assessed at 24 h and the other at 6 days. Pigments (chlorophylls and carotenoids) were found increased at 24 h, but decreased at day 6 in salinity conditions. Sugars (glucose, sucrose, starch but not fructose) increased with stress (24 h and 6 days). Salinity conditions impaired photosystem II (PSII) photochemistry, mostly associated with decrease in Fv′/Fm′ and chlorophyll content (6 days). While hydrogen peroxide levels did not increase above control levels, lipid peroxidation increased, suggesting oxidative damage. In salinity conditions, superoxide dismutase and ascorbate peroxidase showed higher activity in the 24 h timepoint, whereas catalase activity increased at 24 h and 6 days. These observations reveal adaptations of Q. suber to high salinity, nevertheless, the decreased photosynthetic activity and oxidative damages observed suggest that additional studies are required to assess Q. suber adaptation to diverse salinity conditions. Moreover, these data provide more information for future programs of conservation and management of salinity areas in the Mediterranean region, and selection of salinity tolerant species. [ABSTRACT FROM AUTHOR]

Main conclusion: A water-deficit period, leading to stomatal control and overexpression of protective proteins (sHSP and DHN), contributes to olive´s tolerance to later imposed stress episodes. Aquaporins modulation is important in olive recovery. Olive is traditionally cultivated in dry farming or in high water demanding irrigated orchards. The impact of climate change on these orchards remains to unveil, as heat and drought episodes are increasing in the Mediterranean region. To understand how young plants face such stress episodes, olive plants growing in pots were exposed to well-irrigated and non-irrigated treatments. Subsequently, plants from each treatment were either exposed to 40 °C for 2 h or remained under control temperature. After treatments, all plants were allowed to grow under well-irrigated conditions (recovery). Leaves were compared for photosynthesis, relative water content, mineral status, pigments, carbohydrates, cell membrane permeability, lipid peroxidation and expression of the protective proteins' dehydrin (OeDHN1), heat-shock proteins (OeHSP18.3), and aquaporins (OePIP1.1 and OePIP2.1). Non-irrigation, whilst increasing carbohydrates, reduced some photosynthetic parameters to values below the ones of the well-irrigated plants. However, when both groups of plants were exposed to heat, well-irrigated plants suffered more drastic decreases of net CO2 assimilation rate and chlorophyll b than non-irrigated plants. Overall, OeDHN1 and OeHSP18.3 expression, which was increased in non-irrigated treatment, was potentiated by heat, possibly to counteract the increase of lipid peroxidation and loss of membrane integrity. Plants recovered similarly from both irrigation and temperature treatments, and recovery was associated with increased aquaporin expression in plants exposed to one type of stress (drought or heat). These data represent an important contribution for further understanding how dry-farming olive will cope with drought and heat episodes. [ABSTRACT FROM AUTHOR]

Titanium dioxide nanoparticles (TiO2-NP) are increasingly being proposed for nanoagriculture but their effect on photosynthesis is limited and contradictory, mostly regarding putative chronical effects associated to the exposure to the commercial P25 formulation (anatase:rutile). This research aims at evaluating how chronical exposure to P25-NP affect photosynthetic processes in Triticum aestivum. Wheat plants were exposed (from the germination stage) to 0, 5, 50, and 150 mg L−1 P25-NP for 20 days. P25-NP impaired both light-dependent and -independent phases of photosynthesis, decreased chlorophyll a content, maximal and effective efficiency of PSII, net photosynthetic rate, transpiration rate, stomatal conductance, intercellular CO2 concentration, and starch content. On the other hand, no effects were observed in photochemical and in non-photochemical quenching values, on total soluble sugar (TSS) content or in RuBisCO activity. Our results support that the induced decay in chlorophyll a content compromised the electron transport through PSII and that stomatal limitations impaired CO2 assimilation. The decline of starch content seems to be a consequence of its degradation as a mechanism to maintain the TSS levels. Consequently, we propose that photosynthetic related endpoints are sensitive and valuable biomarkers to assess TiO2-NP toxicity. [ABSTRACT FROM AUTHOR]