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The increase in grape berry ripening rates associated to climate change is a growing concern for wine makers as it rises the alcohol content of the wine. The present work studied the combined effects of elevated CO 2 , temperature and UV-B radiation on leaf physiology and berry ripening rates. Three doses of UV-B: 0, 5.98, 9.66 kJ m −2 d −1 , and two CO 2 –temperature regimes: ambient CO 2 -24/14 °C (day/night) (current situation) and 700 ppm CO 2 -28/18 °C (climate change) were imposed to grapevine fruit-bearing cuttings from fruit set to maturity under greenhouse-controlled conditions. Photosynthetic performance was always higher under climate change conditions. High levels of UV-B radiation down regulated carbon fixation rates. A transient recovery took place at veraison, through the accumulation of flavonols and the increase of antioxidant enzyme activities. Interacting effects between UV-B and CO 2 –temperature regimes were observed for the lipid peroxidation, which suggests that UV-B may contribute to palliate the signs of oxidative damage induced under elevated CO 2 –temperature. Photosynthetic and ripening rates were correlated. Thereby, the hastening effect of climate change conditions on ripening, associated to higher rates of carbon fixation, was attenuated by UV-B radiation. [ABSTRACT FROM AUTHOR]

This work aims to characterize the physiological response of grapevine ( Vitis vinifera L.) cv. Tempranillo to UV-B radiation under water deficit conditions. Grapevine fruit-bearing cuttings were exposed to three levels of supplemental biologically effective UV-B radiation (0, 5.98 and 9.66 kJ m −2 day −1 ) and two water regimes (well watered and water deficit), in a factorial design, from fruit-set to maturity under glasshouse-controlled conditions. UV-B induced a transient decrease in net photosynthesis ( A net ), actual and maximum potential efficiency of photosystem II, particularly on well watered plants. Methanol extractable UV-B absorbing compounds (MEUVAC) concentration and superoxide dismutase activity increased with UV-B. Water deficit effected decrease in A net and stomatal conductance, and did not change non-photochemical quenching and the de-epoxidation state of xanthophylls, dark respiration and photorespiration being alternative ways to dissipate the excess of energy. Little interactive effects between UV-B and drought were detected on photosynthesis performance, where the impact of UV-B was overshadowed by the effects of water deficit. Grape berry ripening was strongly delayed when UV-B and water deficit were applied in combination. In summary, deficit irrigation did not modify the adaptive response of grapevine to UV-B, through the accumulation of MEUVAC. However, combined treatments caused additive effects on berry ripening. [ABSTRACT FROM AUTHOR]

Continued emissions of CO2, derived from human activities, increase atmospheric CO2 concentration. The CO2 rise stimulates plant growth and affects yield quality. Effects of elevated CO2 on legume quality depend on interactions with N2-fixing bacteria and mycorrhizal fungi. Growth at elevated CO2 increases photosynthesis under short-term exposures in C3 species. Under long-term exposures, however, plants generally acclimate to elevated CO2 decreasing their photosynthetic capacity. An updated survey of the literature indicates that a key factor, perhaps the most important, that characteristically influences this phenomenon, its occurrence and extent, is the plant source-sink balance. In legumes, the ability of exchanging C for N at nodule level with the N2-fixing symbionts creates an extra C sink that avoids the occurrence of photosynthetic acclimation. Arbuscular mycorrhizal fungi colonizing roots may also result in increased C sink, preventing photosynthetic acclimation. Defoliation (Anthyllis vulneraria, simulated grazing) or shoot cutting (alfalfa, usual management as forage) largely increases root/shoot ratio. During re-growth at elevated CO2, new shoots growth and nodule respiration function as strong C sinks that counteracts photosynthetic acclimation. In the presence of some limiting factor, the legumes response to elevated CO2 is weakened showing photosynthetic acclimation. This survey has identified limiting factors that include an insufficient N supply from bacterial strains, nutrient-poor soils, low P supply, excess temperature affecting photosynthesis and/or nodule activity, a genetically determined low nodulation capacity, an inability of species or varieties to increase growth (and therefore C sink) at elevated CO2 and a plant phenological state or season when plant growth is stopped. [ABSTRACT FROM AUTHOR]

Human activities are increasing atmospheric CO2 concentration and temperature. Related to this global warming, periods of low water availability are also expected to increase. Thus, CO2 concentration, temperature and water availability are three of the main factors related to climate change that potentially may influence crops and ecosystems. In this report, we describe the use of growth chamber -- greenhouses (GCG) and temperature gradient greenhouses (TGG) to simulate climate change scenarios and to investigate possible plant responses. In the GCG, CO2 concentration, temperature and water availability are set to act simultaneously, enabling comparison of a current situation with a future one. Other characteristics of the GCG are a relative large space of work, fine control of the relative humidity, plant fertirrigation and the possibility of light supplementation, within the photosynthetic active radiation (PAR) region and/or with ultraviolet-B (UV-B) light. In the TGG, the three above-mentioned factors can act independently or in interaction, enabling more mechanistic studies aimed to elucidate the limiting factor(s) responsible for a given plant response. Examples of experiments, including some aimed to study photosynthetic acclimation, a phenomenon that leads to decreased photosynthetic capacity under long-term exposures to elevated CO2, using GCG and TGG are reported. [ABSTRACT FROM AUTHOR]

Highlights: [•] Must extractable anthocyanins, colour density and skin flavonols were enhanced by UV-B. [•] The quantitative and qualitative profile of grape skin flavonols were modified by UV-B radiation. [•] The relative abundance of the different forms of flavonols changed proportionally to the dose of UV-B. [•] UV-B had an impact on grape berry amino acid metabolism. [•] UV-B triggered the accumulation of GABA in the pulp, an intermediate in the prevention of oxidative damage. [Copyright &y& Elsevier]

Highlights: [•] Grapevine showed high tolerance to UV-B. [•] Only high UV-B doses transiently reduced grapevine photosynthetic performance, inducing stomatal closure. [•] Differential responses of grapevine to short- and long-term exposures to high UV-B were revealed. [•] High UV-B doses triggered the antioxidant enzyme's response of grapevine, avoiding oxidative damage. [•] UV-B absorbing compounds strongly increased in plants acclimated to UV-B. [Copyright &y& Elsevier]

Abstract: Future climatic conditions, including rising atmospheric CO2 and temperature may increase photosynthesis and, consequently, plant production. A larger knowledge of legume performance under the predicted growth conditions will be crucial for safeguarding crop management and extending the area under cultivation with these plants in the near future. N2 fixation is a key process conditioning plant responsiveness to varying growth conditions. Moreover, it is likely to increase under future environments, due to the higher photosynthate availability, as a consequence of the higher growth rate under elevated CO2. However, as described in the literature, photosynthesis performance is frequently down-regulated (acclimated) under long-term exposure to CO2, especially when affected by stressful temperature and water availability conditions. As growth responses to elevated CO2 are dependent on sink-source status, it is generally accepted that down-regulation occurs in situations with insufficient plant C sink capacity. Alfalfa management involves the cutting of shoots, which alters the source–sink relationship and thus the photosynthetic behaviour. As the growth rate decreases at the end of the pre-cut vegetative growth period, nodulated alfalfa plants show photosynthetic down-regulation, but during regrowth following defoliation, acclimation to elevated CO2 disappears. The shoot harvest also leads to a drop in mineral N uptake and C translocation to the roots, resulting in a reduction in N2 fixation due to the dependence on photosynthate supply to support nodule function. Therefore, the production of new shoots during the first days following cutting requires the utilization of reduced C and N compounds that have been stored previously in reserve organs. The stored reserves are mediated by phytohormones such as methyl jasmonate and abscisic acid and in situations where water stress reduces shoot production this potentially enables the enhancement of taproot protein levels in nodulated alfalfa, which may lead to these plants being in better condition in the following cut/regrowth cycle. Furthering our knowledge of legume performance under predicted climate change conditions will be crucial for the development of varieties with better adaptation that will achieve greater and more efficient production values. Furthermore, for this purpose it will be necessary to improve existing methodologies and create new ones for phenotype characterization. Such knowledge will provide key information for future plant breeding programs. [Copyright &y& Elsevier]

Abstract: Greenhouse experiments were conducted to compare stress effects caused by Verticillium dahliae and drought on gas exchange, chlorophyll (Chl) fluorescence and photosynthetic pigments of pepper plants. Three treatments were compared: Verticillium inoculated plants (+V), non-inoculated well-watered plants (−V) and non-inoculated plants subjected to progressive drought (D). Gas exchange, fluorescence and photosynthetic pigments were measured and represented along a gradient of relative water content (RWC) and stomatal conductance (g s). Net photosynthesis (A) and electron transport rate (ETR) decreased, as RWC and g s declined, similarly in both +V and D plants. However, dark respiration (R D) and photorespiration (R L) tended to increase in inoculated plants compared to those subjected to soil drought, as g s decreased. Photoinhibitory damage was not observed in infected or in droughted plants. Soil drought decreased intrinsic PSII efficiency (Φ exc.), which seemed to result in part from enhanced xanthophyll cycle- and/or lutein-related thermal energy dissipation. Nevertheless, the fact that 1−Φ exc. increased in D only at high values of the de-epoxidation state of the xanthophyll cycle (DPS) suggests that ΔpH could be the major factor controlling thermal energy dissipation in this treatment. By contrast, antheraxanthin, zeaxanthin and lutein, as well as Φ exc., were not markedly affected in +V. Water stress appeared to be the main limitation to photosynthesis in Verticillium infected plants, probably through stomatal closure, together with impaired mesophyll conductance (g m). However, our results indicate differential effects of V. dahliae on dark respiration, photorespiration, g m and on the capability of thermal energy dissipation under low g s values. [Copyright &y& Elsevier]