Although it is established that there exist potential trade‐offs between grain yield and grain quality in wheat exposed to elevated carbon dioxide (CO2) and ozone (O3), their underlying causes remain ...poorly explored. To investigate the processes affecting grain quality under altered CO2 and O3, we analysed 57 experiments with CO2 or O3 exposure in different exposure systems. The study covered 24 cultivars studied in 112 experimental treatments from 11 countries. A significant growth dilution effect on grain protein was found: a change in grain yield of 10% by O3 was associated with a change in grain protein yield of 8.1% (R2 = 0.96), whereas a change in yield effect of 10% by CO2 was linked to a change in grain protein yield effect of 7.5% (R2 = 0.74). Superimposed on this effect, elevated CO2, but not O3, had a significant negative effect on grain protein yield also in the absence of effects on grain yield, indicating that there exists a process by which CO2 restricts grain protein accumulation, which is absent for O3. Grain mass, another quality trait, was more strongly affected by O3 than grain number, whereas the opposite was true for CO2. Harvest index was strongly and negatively influenced by O3, but was unaffected by CO2. We conclude that yield vs. protein trade‐offs for wheat in response to CO2 and O3 are constrained by close relationships between effects on grain biomass and less than proportional effects on grain protein. An important and novel finding was that elevated CO2 has a direct negative effect on grain protein accumulation independent of the yield effect, supporting recent evidence of CO2‐induced impairment of nitrate uptake/assimilation. Finally, our results demonstrated that processes underlying responses of grain yield vs. quality trade‐offs are very different in wheat exposed to elevated O3 compared with elevated CO2.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Air pollution levels (NO2, PAHs, O3) were investigated, before (BLE) and after (ALE) leaf emergence, in the urban landscape of Gothenburg, Sweden. The aims were to study the 1) spatial and temporal ...variation in pollution levels between urban green areas, 2) effect of urban vegetation on air pollution levels at the same distance from a major emission source (traffic route), 3) improvement of urban air quality in urban parks compared to adjacent sites near traffic, 4) correlation between air pollution and noise in a park. O3 varied little over the urban landscape. NO2 varied strongly and was higher in situations strongly influenced by traffic. Four PAH variables were included: total PAH, total particle-bound PAH, the quantitatively important gaseous phenanthrene and the highly toxic particle-bound benzo(a)pyrene. The variation of PAHs was similar to NO2, but for certain PAHs the difference between highly and less polluted sites was larger than for NO2. At a vegetated site, NO2 and particulate PAH levels were lower than at a non-vegetated site at a certain distance from a busy traffic route. This effect was significantly larger ALE compared to BLE for NO2, indicating green leaf area to be highly significant factor for air quality improvement. For particulate PAHs, the effect was similar BLE and ALE, indicating that tree bark and branches also could be an important factor in reducing air pollution. Parks represented considerably cleaner local environments (park effect), which is likely to be a consequence of both a dilution (distance effect) and deposition. Noise and air pollution (NO2 and PAH) levels were strongly correlated. Comparison of noise levels BLE and ALE also showed that the presence of leaves significantly reduced noise levels. Our results are evidence that urban green spaces are beneficial for urban environmental quality, which is important to consider in urban planning.
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•NO2 and benzo(a)pyrene levels were reduced by vegetation near a busy traffic route.•Parks had substantially lower NO2 and PAH levels than adjacent areas near traffic.•Pollutant exposure can be substantially reduced by separating people from traffic.•PAH levels in the city were strongly correlated with NO2.•Leaves reduce noise levels at frequencies that are important for traffic noise.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Tropospheric ozone is known to adversely affect crops and other vegetation. Most studies have focussed on the effects of elevated ozone levels vs. present ambient. We investigated the effect of ...present ambient surface ozone (O3) concentrations vs. preindustrial on a range of agronomically important response variables in field-grown wheat, using results from 33 experiments (representing 9 countries, 3 continents, 17 cultivars plus one set of 4 cultivars) having both charcoal filtered (CF) and non-filtered (NF) air treatments. Average filtration efficiency was 62%, reducing the O3 concentration from 35.6±10.6SDppb in NF to 13.7±8.8SDppb in CF. Average CF concentrations were in the range of levels believed to represent pre-industrial conditions, while NF concentrations were 7% lower than in the ambient air at plant height on the experimental sites. NF had significant (p<0.05) negative effects compared to CF on grain yield (−8.4%), grain mass (−3.7%), harvest index (−2.4%), total above-ground biomass (−5.4%), starch concentration (−3.0%), starch yield (−10.9%), and protein yield (−6.2%). No significant effect was found for grain number and protein concentration. There was a significant relationship between the effect of filtration on grain yield and the difference in O3 concentration between NF and CF treatments. The average yield loss per ppb O3 removed was 0.38% and did not systematically vary with year of experiment (ranging from 1982 to 2010) or with the average O3 level in the experiments. Although there are many differences among the field experiments included in this meta-analysis (e.g. genotype, degree of O3 pollution of the site and year, nutrient and soil condition, filtration efficiency), our study clearly shows that there is a consistent and significant effect of present ambient O3 exposure on a range of important response variables in wheat, the most strongly affected being starch yield.
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•The effects of current vs. preindustrial ozone on wheat were investigated.•Compared to preindustrial levels, current ozone negatively affected wheat growth, yield and quality.•The effect on yield was related to the amount of ozone removed by filtration.•The effect on yield was not related to the age of the cultivar.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Data from experiments where field-grown wheat was exposed to ozone were collated in order to compare the effects in Europe, Asia and North America using dose-response regression. In addition to grain ...yield, average grain mass and harvest index were included to reflect the influence of ozone on the crop growth pattern. In order to include as many experiments as possible, daytime average ozone concentration was used as the ozone exposure index, but AOT40, estimated from average ozone concentrations, was also used to compare the performance of the two exposure metrics. The response to ozone differed significantly between the continents only for grain yield when using AOT40 as the exposure index. North American wheat was less sensitive than European and Asian that responded similarly. The variation in responses across all three continents was smallest for harvest index, followed by grain mass and grain yield. The highly consistent effect on harvest index shows that not only effects on biomass accumulation, but also on the partitioning of biomass, are important for the ozone-induced grain yield loss in wheat. The average duration of daily ozone exposure was longer in European experiments compared to North American and Asian. It cannot be excluded that this contributed to the indicated higher ozone sensitivity in European wheat in relation to North American. The main conclusions from this study are that on the average the response of wheat to ozone was lower for the older North American experiments and that the ozone response of the growth pattern reflected by grain mass and harvest index did not differ between continents.
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•Lower ozone sensitivity of grain yield in North American compared to European and Asian wheat experiments•Ozone response did not differ between continents for grain mass and harvest index•The exposure index AOT40 was superior to daytime average ozone concentration in explaining observed effects
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We synthesized the effects of ozone on wheat quality based on 42 experiments performed in Asia, Europe and North America. Data were analysed using meta-analysis and by deriving response functions ...between observed effects and daytime ozone concentration. There was a strong negative effect on 1000-grain weight and weaker but significant negative effects on starch concentration and volume weight. For protein and several nutritionally important minerals (K, Mg, Ca, P, Zn, Mn, Cu) concentration was significantly increased, but yields were significantly decreased by ozone. For other minerals (Fe, S, Na) effects were not significant or results inconclusive. The concentration and yield of potentially toxic Cd were negatively affected by ozone. Some baking properties (Zeleny value, Hagberg falling number) were positively influenced by ozone. Effects were similar in different exposure systems and for spring and winter wheat. Ozone effects on quality should be considered in future assessments of food security/safety.
•Ozone reduces starch concentration, 1000-grain weight and volume weight of wheat.•Ozone enhances concentration, but reduces yield of several minerals and protein.•Some baking properties are positively affected by ozone.
Ozone negatively affects quality traits such as 1000-grain weight, volume weight and starch concentration in wheat, while baking properties are positively affected.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A stomatal ozone (O3) flux-response relationship for relative yield of maize was established by parameterizing a Jarvis stomatal conductance model. For the function (fVPD) describing the limitation ...of stomatal conductance by vapor pressure deficit (VPD, kPa), cumulative VPD during daylight hours was superior to hourly VPD. The latter function is proposed as a methodological improvement of this multiplicative model when stomatal conductance peaks during the morning and it is reduced later as it is the case of maize in this experiment. The model agreed relatively well with the measured stomatal conductance (R2 = 0.63). Based on the comparison of R2 values of the response functions, POD6 (Phytotoxic Ozone Dose over an hourly threshold 6 nmol m−2 s−1) and AOT40 (accumulated hourly O3 concentrations over a threshold of 40 ppb) performed similarly. The critical levels based on POD6 and AOT40 for 5% reduction in maize yield were 1.17 mmol m−2 PLA and 8.70 ppm h, respectively. In comparison with other important crops, the ranking of sensitivity of maize strongly differed depending on the O3 metric used, AOT40 or POD6. The newly proposed response functions are relevant for O3 risk assessment for this crop in Asia.
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•The Jarvis stomatal conductance model of maize was parameterized.•Cumulative VPD during daylight hours was superior to hourly VPD for fVPD.•An O3 flux-yield response relationship was developed for maize for the first time.•The performance of O3 exposure- and flux–based approaches was similar.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Nutrient elements generally have higher harvest index (HI) than non-essentials elements.•Element HI is strongly element specific.•Ozone significantly reduces HI for nutrient elements and Cd.•No ...ozone effect on total aboveground element pool, except for P.
Wheat efficiently remobilize and allocate a large fraction of aboveground biomass and nutrients into their grains during maturation. This senescence process has been streamlined through crop breeding, which lead to increasing harvest index (HI) for biomass. With field data from two ozone exposure experiments, we derived HI for 13 elements, both nutrients and non-essential, to determine how efficiently they are allocated into the wheat grain in two different agro-ecological environments (Sweden and China) and under different ozone exposure regimes. Element HI ranged from 10 to 90 %, with highest rates for P, N and Zn (90 %, 80 % and 70 %, respectively), while HI was low for the non-mobile elements Ba, Sr and Ca (<10 %). HI for biomass was about 50 %, and the non-essential and toxic element Cd was in the same range (∼40 %). Overall element HI was very similar in Chinese and Swedish wheat cultivars. This was also the case when comparing the two Chinese genotypes. We conclude that element HI for wheat crops are highly element specific and not strongly dependent on site or cultivar. Ozone exposure significantly reduced HI for both macronutrients (Ca, K, Mg, N, P) and micronutrients (Cu, Mn, Mo, Zn), but also for Cd, while there was no ozone effect on the total aboveground pool for any element except P and Ba. Consequently, the reduction in grain element yield induced by elevated ozone, observed in previous studies, can be explained by lower remobilization rates rather than reduced total uptake. Our results provide new insights of nutrient use efficiency in wheat crops in general and under ozone exposure, which can be implemented in crop modelling and also useful for breeding strategies aiming to improve the nutritional value of food crops.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Crop quality under rising atmospheric CO2 Uddling, Johan; Broberg, Malin C; Feng, Zhaozhong ...
Current opinion in plant biology,
10/2018, Volume:
45
Journal Article
Peer reviewed
•Elevated CO2 decreases the concentrations of most nutrients in non-legume C3 crops.•The effects are correlated for nutrients mostly found in proteins: N, Zn, Fe, S.•None of the suggested mechanisms ...and processes can explain the effect on N.•Decreased concentrations of protein, Zn and Fe have implications for food security.
Crops grown under elevated CO2 (eCO2) typically exhibit enhanced yields but at the same time decreased nutritional quality. The latter effect has often been explained as a growth dilution phenomenon, but this cannot be the only process involved since crop nutrient concentrations are decreased also when production is unaffected by eCO2. We review the current knowledge on eCO2 effects on crop nutritional quality with focus on the current understanding of the possible mechanisms and processes causing these effects. Emphasis is on crop nitrogen (N) and protein concentrations but effects on other nutrients and how they compare with those on N are also covered.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
An important ecosystem service provided by urban trees is the cooling effect caused by their transpiration. The aim of this study was to quantify the magnitude of daytime and night-time transpiration ...of common urban tree species in a high latitude city (Gothenburg, Sweden), to analyse the influence of weather conditions and surface permeability on the tree transpiration, and to find out whether tree transpiration contributed to daytime or nocturnal cooling. Stomatal conductance and leaf transpiration at day and night were measured on mature street and park trees of seven common tree species in Gothenburg: Tilia europaea, Quercus robur, Betula pendula, Acer platanoides, Aesculus hippocastanum, Fagus sylvatica and Prunus serrulata. Transpiration increased with vapour pressure deficit and photosynthetically active radiation. Midday rates of sunlit leaves ranged from less than 1 mmol m⁻² s⁻¹ (B. pendula) to over 3 mmol m⁻² s⁻¹ (Q. robur). Daytime stomatal conductance was positively related to the fraction of permeable surfaces within the vertically projected crown area. A simple estimate of available rainwater, comprising of precipitation sum and fractional surface permeability within the crown area, was found to explain 68 % of variation in midday stomatal conductance. Night-time transpiration was observed in all studied species and amounted to 7 and 20 % of midday transpiration of sunlit and shaded leaves, respectively. With an estimated night-time latent heat flux of 24 W m⁻², tree transpiration significantly increased the cooling rate around and shortly after sunset, but not later in the night. Despite a strong midday latent heat flux of 206 W m⁻², a cooling effect of tree transpiration was not observed during the day.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Five modern cultivars of winter wheat (Triticum aestivum L.): Yangmai16 (Y16), Yangmai 15 (Y15), Yangfumai 2 (Y2), Yannong 19 (Y19) and Jiaxing 002 (J2) were investigated to determine the impacts of ...elevated ozone concentration (E-O3) on photosynthesis-related parameters and the antioxidant system under fully open-air field conditions in China. The plants were exposed to E-O3 at 1.5 times the ambient ozone concentration (A-O3) from the initiation of tillering to final harvest. Pigments, gas exchange rates, chlorophyll a fluorescence, antioxidants contents, antioxidative enzyme activity and lipid oxidation were measured in three replicated plots throughout flag leaf development. Results showed that significant O3 effects on most variables were only found during the mid-grain filling stage. Across five cultivars, E-O3 significantly accelerated leaf senescence, as indicated by increased lipid oxidation as well as faster declines in pigment amounts and photosynthetic rates. The lower photosynthetic rates were mainly due to non-stomatal factors, e.g. lower maximum carboxylation capacity and electron transport rates. There were strong interactions between O3 and cultivar in photosynthetic pigments, light-saturated photosynthesis rate and chlorophyll a fluorescence with O3-sensitive (Y19, Y2 and Y15) and O3-tolerant (J2, Y16) cultivars being clearly differentiated in their responses to E-O3. E-O3 significantly influenced the antioxidative enzymes but not antioxidant contents. Significant interactions between O3 and cultivar were found in antioxidative enzymes, such as SOD and CAT, but not in stomatal conductance (gs). Therefore, it can be concluded that antioxidative enzymes rather than gs or antioxidants are responsible for the differential responses to E-O3 among cultivars. These findings provide important information for the development of accurate modeling O3 effects on crops, especially with respect to the developmental stage when O3 damage to photosynthesis becomes manifest.
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•5 modern cultivars of wheat were investigated under fully open-air field conditions.•Significant O3 effects were only found during the mid-grain filling stage.•The lower photosynthetic rates were mainly due to nonstomatal factors.•Antioxidative enzymes contributed to the differential response to E-O3 among cultivars.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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