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For many Indigenous children living in remote communities, the prerequisites to achieving strong language and learning outcomes include the maintenance of their first languages and progress in learning English as an additional language. This paper reports on data from a Linkage study conducted with families at two Families as First Teachers (FaFT) playgroups in two remote Northern Territory communities. The data highlight the ways parents and carers encouraged very young children to engage in home languages as a foundation on which to develop skills in English during play and book reading activities. Transcripts of mother-child book reading and play sessions and reflections of FaFT Family Liaison Officers are examined to explore the language interactions and the strategies used by mothers to support children's multilingual learning. The data highlight the importance of early childhood teaching and learning that honours children's linguistic and cultural resources and prioritises families' aspirations for children's multilingual language learning.

Surface ozone (O 3) is the primary air pollutant threatening global vegetation. It typically reduces the photosynthetic rate and stomatal conductance, leading to changes in carbon, water, and energy cycles; vegetation structure and composition; and climate. Several parameterization schemes have been developed to integrate the photosynthetic and stomatal responses to O 3 exposure in regional and global process-based models to simulate time- and space-varying O 3 plant damage and its cascading dynamic influence. However, these schemes are calibrated based on limited observations and often fail to reproduce the response relationships in observations, impeding accurate assessments of the role of O 3 plant damage in the Earth system. This study proposes a new parameterization scheme to utilize the extensive observations from O 3 fumigation experiments to inform large-scale modeling. It is built on 4210 paired data points of photosynthetic and stomatal responses compiled from the peer-reviewed literature, more than 6 times larger than those employed in earlier schemes. Functions of phytotoxic O 3 dose (POD) are found to accurately reproduce the statistically significant linear or nonlinear relationships observed between POD and either relative leaf photosynthetic rate or relative stomatal conductance for needleleaf trees, broadleaf trees, shrubs, grasses, and crops. These eliminate the practice in earlier schemes of setting response functions as constants and applying the response function from one vegetation type to another. It outperforms the old scheme in the Community Land Model (CLM), which skillfully reproduces the observed response for crop photosynthetic rate only. The nonlinear response functions we developed depict decreasing plant sensitivity with increases in POD, enabling models to implicitly capture the variability in plant ozone tolerance and the shift among plant species for both intra- and inter-PFTs (plant functional types) within a vegetation type observed in the real world. Then, the new scheme is incorporated into the Community Earth System Model version 2.2 (CESM2.2), specifically its land component CLM5, to quantify the global impacts of present-day O 3 plant damage by comparing the simulations with and without O 3 plant damage. Results show that O 3 exposure reduces the global leaf photosynthetic rate by 8.5 % and stomatal conductance by 7.4 %, around half the estimates using the old scheme. Furthermore, the new scheme improves global gross primary productivity (GPP) simulations, decreasing RMSE by 11.1 % relative to simulations without O 3 plant damage and by 11.7 % compared to the old scheme. These results underscore the importance of including O 3 plant damage in large-scale process-based models and the effectiveness of the new scheme in assessing and projecting globally the role of O 3 plant damage in the Earth system. [ABSTRACT FROM AUTHOR]

Tropospheric ozone (O3) is a global air pollutant that adversely affects plant growth. Whereas the impacts of O3 have previously been examined for some tropical commodity crops, no information is available for the pantropical crop, banana (Musa spp.). To address this, we exposed Australia's major banana cultivar, Williams, to a range of [O3] in open top chambers. In addition, we examined 46 diverse Musa lines growing in a common garden for variation in three traits that are hypothesised to shape responses to O3: (1) leaf mass per area; (2) intrinsic water use efficiency; and (3) total antioxidant capacity. We show that O3 exposure had a significant effect on the biomass of cv. Williams, with significant reductions in both pseudostem and sucker biomass with increasing [O3]. This was accompanied by a significant increase in total antioxidant capacity and phenolic concentrations in older, but not younger, leaves, indicating the importance of cumulative O3 exposure. Using the observed trait diversity, we projected O3 tolerance among the 46 Musa lines growing in the common garden. Of these, cv. Williams ranked as one of the most O3-tolerant cultivars. This suggests that other genetic lines could be even more susceptible, with implications for banana production and food security throughout the tropics. Tropospheric ozone (O3) is a global air pollutant that adversely affects plant growth and productivity. Whereas impacts of O3 have previously been examined in some commodity crops, no information is currently available for the pantropical staple crop, banana (Musa spp.). In this study, we have demonstrated the scale and possible prevalence of O3 susceptibility in bananas, with implications for production and food security throughout the tropics. [ABSTRACT FROM AUTHOR]

Restoration ecologists have local‐ to global‐scale ambitions in a policy framework of sustainable development goals and reversing biodiversity loss. Emphasis is given to environmental alteration, typically considering land degradation and climate change. Other related environmental drivers, such as pollution, receive less attention. Here we emphasize that terrestrial restoration discourse needs to consider tropospheric ozone (O3) pollution. O3's pervasive influence on plants and other ecosystem components provides for the possibility of consequences at community and ecosystem levels. The precursor chemicals that lead to O3 formation are increasing, precipitously so in rapidly industrializing regions of the world. Yet, a review of critical restoration guidance and journals suggests that because O3 is out of sight, it remains out of mind. Based on a narrative cross‐discipline literature review, we examine: (1) How O3 could affect the achievement of restoration goals and (2) How restoration interventions could feedback on tropospheric O3. Evidence, currently limited, suggests that O3 could impair the achievement of restoration goals to as great an extent as other drivers, but, in general, we lack direct quantification. Restoration interventions (e.g. tree planting) that may be considered successful can actually exacerbate O3 pollution with negative consequences for food security and human health. These wide‐ranging effects, across multiple goals, mean that O3 is not out of scope for restoration science, policy, and practice. In detailing a strategic ozone‐aware restoration agenda, we suggest how restoration science and policy can quantify O3's influence, while outlining steps practitioners can take to adapt to/mitigate the impacts of O3 pollution. [ABSTRACT FROM AUTHOR]

The sensitivity of photosynthesis to temperature has been identified as a key uncertainty for projecting the magnitude of the terrestrial carbon cycle response to future climate change. Although thermal acclimation of photosynthesis under rising temperature has been reported in many tree species, whether tropospheric ozone (O3) affects the acclimation capacity remains unknown. In this study, temperature responses of photosynthesis (light‐saturated rate of photosynthesis (Asat), maximum rates of RuBP carboxylation (Vcmax), and electron transport (Jmax) and dark respiration (Rdark) of Populus tremula exposed to ambient O3 (AO3, maximum of 30 ppb) or elevated O3 (EO3, maximum of 110 ppb) and ambient or elevated temperature (ambient +5°C) were investigated in solardomes. We found that the optimum temperature of Asat (ToptA) significantly increased in response to warming. However, the thermal acclimation capacity was reduced by O3 exposure, as indicated by decreased ToptA, and temperature optima of Vcmax (ToptV) and Jmax (ToptJ) under EO3. Changes in both stomatal conductance (gs) and photosynthetic capacity (Vcmax and Jmax) contributed to the shift of ToptA by warming and EO3. Neither Rdark measured at 25°C (Rdark25) nor the temperature response of Rdark was affected by warming, EO3, or their combination. The responses of Asat, Vcmax, and Jmax to warming and EO3 were closely correlated with changes in leaf nitrogen (N) content and N use efficiency. Overall, warming stimulated growth (leaf biomass and tree height), whereas EO3 reduced growth (leaf and woody biomass). The findings indicate that thermal acclimation of Asat may be overestimated if the impact of O3 pollution is not taken into account. [ABSTRACT FROM AUTHOR]

Northern, Southern and Equatorial Africa have been identified as among the regions most at risk from very high ozone concentrations. Whereas we know that many crop cultivars from Europe, north America and Asia are sensitive to ozone, almost nothing is known about the sensitivity of staple food crops in Africa to the pollutant. In this study cultivars of the African staple food crops, Triticum aestivum (wheat), Eleusine coracana (finger millet), Pennisetum glaucum (pearl millet) and Phaseolus vulgaris (bean) were exposed to an episodic ozone regime in solardomes in order to assess whether African crops are sensitive to ozone pollution. Extensive visible leaf injury due to ozone was shown for many cultivars, indicating high sensitivity to ozone. Reductions in total yield and 1,000‐grain weight were found for T. aestivum and P. vulgaris, whereas there was no effect on yield for E. coracana and P. glaucum. There were differences in sensitivity to ozone for different cultivars of an individual crop, indicating that there could be possibilities for either cultivar selection or selective crop breeding to reduce sensitivity of these crops to ozone. [ABSTRACT FROM AUTHOR]

Nitrogen deposition and tropospheric ozone are important drivers of vegetation damage, but their interactive effects are poorly understood. This study assessed whether long-term nitrogen deposition altered sensitivity to ozone in a semi-natural vegetation community. Mesocosms were collected from sand dune grassland in the UK along a nitrogen gradient (5–25 kg N/ha/y, including two plots from a long-term experiment), and fumigated for 2.5 months to simulate medium and high ozone exposure. Ozone damage to leaves was quantified for 20 ozone-sensitive species. Soil solution dissolved organic carbon (DOC) and soil extracellular enzymes were measured to investigate secondary effects on soil processes. Mesocosms from sites receiving the highest N deposition showed the least ozone-related leaf damage, while those from the least N-polluted sites were the most damaged by ozone. This was due to differences in community-level sensitivity, rather than species-level impacts. The N-polluted sites contained fewer ozone-sensitive forbs and sedges, and a higher proportion of comparatively ozone-resistant grasses. This difference in the vegetation composition of mesocosms in relation to N deposition conveyed differential resilience to ozone. Mesocosms in the highest ozone treatment showed elevated soil solution DOC with increasing site N deposition. This suggests that, despite showing relatively little leaf damage, the 'ozone resilient' vegetation community may still sustain physiological damage through reduced capacity to assimilate photosynthate, with its subsequent loss as DOC through the roots into the soil. We conclude that for dune grassland habitats, the regions of highest risk to ozone exposure are those that have received the lowest level of long-term nitrogen deposition. This highlights the importance of considering community- and ecosystem-scale impacts of pollutants in addition to impacts on individual species. It also underscores the need for protection of 'clean' habitats from air pollution and other environmental stressors. Image 1 • The N-polluted sites contained fewer ozone-sensitive forbs and sedges. • Vegetation composition in relation to N deposition conveyed differential ozone-resilience. • Mesocosms in the highest ozone treatment showed elevated soil solution DOC. For dune grassland habitats, the regions of highest risk to ozone exposure are those that have received the lowest level of long-term nitrogen deposition. [ABSTRACT FROM AUTHOR]

Abstract To investigate whether nitrogen (N) load affects the ozone (O 3) stomatal flux-effect relationship for birch biomass, three-year old birch saplings were exposed to seven different O 3 profiles (24 h mean of 35–66 ppb) and four different N loads (10, 30, 50 and 70 kg ha−1 yr−1) in precision-controlled hemispherical glasshouses (solardomes) in 2012 and 2013. Stomatal conductance (g s) under optimal growth conditions was stimulated by enhanced N supply but was not significantly affected by enhanced O 3 exposure. Birch root, woody (stem + branches) and total biomass (root + woody) were not affected by the Phytotoxic Ozone Dose (POD 1 SPEC) after two seasons of O 3 exposure, and enhanced N supply stimulated biomass production independent of POD 1 SPEC (i.e. there were no POD 1 SPEC × N interactions). There was a strong linear relationship between the stem cross-sectional area and tree biomass at the end of the experiment, which was not affected by O 3 exposure or N load. Enhanced N supply stimulated the stem cross-sectional area at the end of season 2, but not at the end of season 1, which suggests a time lag before tree biomass responded to enhanced N supply. There was no significant effect of POD 1 SPEC on stem cross-sectional area after either the first or second growing season of the experiment. Contrasting results reported in the literature on the interactive impacts of O 3 and N load on tree physiology and growth are likely due to species-specific responses, different duration of the experiments and/or a limitation of the number of O 3 and N levels tested. Graphical abstract Unlabelled Image Highlights • O 3 flux-effect relationships investigated for birch at 7 O 3 profiles and 4 N loads • g s under optimal conditions was stimulated by N but not affected by O 3. • O 3 flux-effect relationships for biomass were not affected by N supply. • O 3 reduced stem cross-sectional area after the first season only. • N stimulation of stem cross-sectional area increased in the second season. [ABSTRACT FROM AUTHOR]

Abstract Reduced belowground carbon (C) allocation by plants exposed to ozone may change properties and activities of the microbial community in soils. To investigate how soil microbial biomass and extracellular enzyme activities respond to elevated ozone, we collected soils from a temperate grassland after four years of ozone exposure under fully open-air field conditions. We measured soil microbial biomass, the metabolism of low molecular weight C substrates and hydrolytic extracellular enzyme activities in both bulk soil and isolated aggregates to assess changes in microbial activity and community function. After four years of elevated ozone treatment, soil total organic C was reduced by an average of 20% compared with ambient condition. Elevated ozone resulted in a small but insignificant reduction (4–10%) in microbial biomass in both bulk soil and isolated aggregates. Activities of extracellular enzymes were generally not affected by elevated ozone, except β -glucosidase, whose activity in bulk soil was significantly lower under elevated ozone than ambient condition. Activities of β -glucosidase, leucine aminopeptidase and acid phosphatase were higher in microaggregates (<0.25 mm) as compared to macroaggregates (>0.25 mm). Elevated ozone had no effects on mineralization rates of low molecular weight C substrates in both bulk soil and isolated aggregates. We therefore conclude that the size and activity rather than function of the soil microbial community in this semi-natural grassland are altered by elevated ozone. Graphical abstract Unlabelled Image Highlights • A temperate grassland was exposed to ozone for 4 years under field conditions. • Soil total carbon and β-glucosidase activity were decreased under elevated ozone. • Neither ozone nor its interaction with aggregate size affected microbial activities. • Elevated ozone could alter the size and activity of soil microbial community. [ABSTRACT FROM AUTHOR]

Abstract: Introduction of high‐performing crop cultivars and crop/soil water management practices that increase the stomatal uptake of carbon dioxide and photosynthesis will be instrumental in realizing the United Nations Sustainable Development Goal (SDG) of achieving food security. To date, however, global assessments of how to increase crop yield have failed to consider the negative effects of tropospheric ozone, a gaseous pollutant that enters the leaf stomatal pores of plants along with carbon dioxide, and is increasing in concentration globally, particularly in rapidly developing countries. Earlier studies have simply estimated that the largest effects are in the areas with the highest ozone concentrations. Using a modelling method that accounts for the effects of soil moisture deficit and meteorological factors on the stomatal uptake of ozone, we show for the first time that ozone impacts on wheat yield are particularly large in humid rain‐fed and irrigated areas of major wheat‐producing countries (e.g. United States, France, India, China and Russia). Averaged over 2010–2012, we estimate that ozone reduces wheat yields by a mean 9.9% in the northern hemisphere and 6.2% in the southern hemisphere, corresponding to some 85 Tg (million tonnes) of lost grain. Total production losses in developing countries receiving Official Development Assistance are 50% higher than those in developed countries, potentially reducing the possibility of achieving UN SDG2. Crucially, our analysis shows that ozone could reduce the potential yield benefits of increasing irrigation usage in response to climate change because added irrigation increases the uptake and subsequent negative effects of the pollutant. We show that mitigation of air pollution in a changing climate could play a vital role in achieving the above‐mentioned UN SDG, while also contributing to other SDGs related to human health and well‐being, ecosystems and climate change. [ABSTRACT FROM AUTHOR]

Ground-level ozone (O 3 ) concentrations and atmospheric nitrogen (N) deposition rates have increased strongly since the 1950s. Rising ground-level O 3 concentrations and atmospheric N deposition both affect plant physiology and growth, however, impacts have often been studied in isolation rather than in combination. In addition, studies are often limited to a control treatment and one or two elevated levels of ozone and/or nitrogen supply. In the current study, three-year old Betula pendula saplings were exposed to seven different O 3 profiles (24 h mean O 3 concentration of 36–68 ppb in 2013, with peaks up to an average of 105 ppb) in precision-controlled hemispherical glasshouses (solardomes) and four different N loads (10, 30, 50 or 70 kg N ha −1 y −1 ) in 2012 and 2013. Here we report on the effects of enhanced O 3 concentrations and N load on leaf traits and gas exchange in leaves of varying age and developmental stage in 2013. The response of leaf traits to O 3 (but not N) vary with leaf developmental stage. For example, elevated O 3 did not affect the chlorophyll content of the youngest fully expanded leaf, but it reduced the chlorophyll content and photosynthetic parameters in aging leaves, relatively more so later than earlier in the growing season. Elevated O 3 enhanced the N content of senesced leaves prior to leaf fall, potentially affecting subsequent N cycling in the soil. Enhanced N generally stimulated the chlorophyll content and photosynthetic capacity. Whilst elevated O 3 reduced the light-saturated rate of photosynthesis (A sat ) in aging leaves, it did not affect stomatal conductance (g s ). This suggests that photosynthesis and g s are not closely coupled at elevated O 3 under-light saturating conditions. We did not observe any interactions between O 3 and N regarding photosynthetic parameters (V c,max , J max , A sat ), chlorophyll content, g s , N content in senesced leaves and leaf number. Hence, the sensitivity of these leaf traits to O 3 in young silver birch trees is neither reduced nor enhanced by N load. [ABSTRACT FROM AUTHOR]

Risks associated with exposure of individual plant species to ozone (O3) are well documented, but implications for terrestrial biodiversity and ecosystem processes have received insufficient attention. This is an important gap because feedbacks to the atmosphere may change as future O3 levels increase or decrease, depending on air quality and climate policies. Global simulation of O3 using the Community Earth System Model ( CESM) revealed that in 2000, about 40% of the Global 200 terrestrial ecoregions ( ER) were exposed to O3 above thresholds for ecological risks, with highest exposures in North America and Southern Europe, where there is field evidence of adverse effects of O3, and in central Asia. Experimental studies show that O3 can adversely affect the growth and flowering of plants and alter species composition and richness, although some communities can be resilient. Additional effects include changes in water flux regulation, pollination efficiency, and plant pathogen development. Recent research is unraveling a range of effects belowground, including changes in soil invertebrates, plant litter quantity and quality, decomposition, and nutrient cycling and carbon pools. Changes are likely slow and may take decades to become detectable. CESM simulations for 2050 show that O3 exposure under emission scenario RCP8.5 increases in all major biomes and that policies represented in scenario RCP4.5 do not lead to a general reduction in O3 risks; rather, 50% of ERs still show an increase in exposure. Although a conceptual model is lacking to extrapolate documented effects to ERs with limited or no local information, and there is uncertainty about interactions with nitrogen input and climate change, the analysis suggests that in many ERs, O3 risks will persist for biodiversity at different trophic levels, and for a range of ecosystem processes and feedbacks, which deserves more attention when assessing ecological implications of future atmospheric pollution and climate change. [ABSTRACT FROM AUTHOR]

Increasing tropospheric ozone poses a potential threat to both above- and belowground components of the terrestrial biosphere. Microorganisms are the main drivers of soil ecological processes, however, the link between soil microbial communities and ecological functions under elevated ozone remains poorly understood. In this study, we assessed the responses of three crop seedlings (i.e., soybean, maize, and wheat) growth and soil microbial communities to elevated ozone (40 ppb O 3 above ambient air) in a pot experiment in the solardomes. Results showed that elevated ozone adversely affected ecosystem multifunctionality by reducing crop biomass, inhibiting soil extracellular enzyme activities, and altering nutrient availability. Elevated ozone increased bacterial and fungal co-occurrence network complexity, negatively correlated with ecosystem multifunctionality. Changes in the relative abundance of some specific bacteria and fungi were associated with multiple ecosystem functioning. In addition, elevated ozone significantly affected fungal community composition but not bacterial community composition and microbial alpha-diversity. Crop type played a key role in determining bacterial alpha-diversity and microbial community composition. In conclusion, our findings suggest that short-term elevated ozone could lead to a decrease in ecosystem multifunctionality associated with changes in the complexity of microbial networks in soils. • Elevated ozone reduced ecosystem multifunctionality. • Changes in microbial community composition were linked to ecosystem functioning. • Elevated ozone negatively affected crop seedling growth and soil microbial activity. • Crop type shaped soil microbial community composition. [ABSTRACT FROM AUTHOR]

In this study we have demonstrated that rising background ozone has the potential to reduce grassland forage quality and explored the implications for livestock production. We analysed pasture samples from seven ozone exposure experiments comprising mesotrophic, calcareous, haymeadow and sanddune unimproved grasslands conducted in open-top chambers, solardomes and a field release system. Across all grassland types, there were significant increases in acid detergent fibre, crude fibre and lignin content with increasing ozone concentration, resulting in decreased pasture quality in terms of the metabolisable energy content of the vegetation. We derived a dose-response function for metabolisable energy of the grassland with ozone concentration, applicable to a range of grassland types, and used this to predict effects on pasture quality of UK vegetation at 1 km resolution using modelled ozone data for 2007 and for predicted higher average ozone concentrations in 2020. This showed a potential total reduction in lamb production in the UK of approximately 4% in 2020 compared to 2007. The largest impacts were in geographical areas of modest ozone increases between the two years, but where large numbers of lambs were present. For an individual farmer working to a very small cost margin this could represent a large reduction in profit, both in regions where the impacts per lamb and those where the impacts per km 2 of grazing land are largest. In the short term farmers could adapt their lamb management in response to changed forage quality by additional supplementary feed of high metabolisable energy content. Nationally this increase in annual additional feed in 2020 compared to 2007 would be 2,166 tonnes (an increase of 0.7%). Of added concern are the longer-term consequences of continual deterioration of pasture quality and the implications for changes in farming practices to compensate for potential reductions in livestock production capacity. [ABSTRACT FROM AUTHOR]

This paper provides a process-oriented perspective on the combined effects of ozone (O 3 ), climate change and/or nitrogen (N) on vegetation. Whereas increasing CO 2 in controlled environments or open-top chambers often ameliorates effects of O 3 on leaf physiology, growth and C allocation, this is less likely in the field. Combined responses to elevated temperature and O 3 have rarely been studied even though some critical growth stages such as seed initiation are sensitive to both. Under O 3 exposure, many species have smaller roots, thereby enhancing drought sensitivity. Of the 68 species assessed for stomatal responses to ozone, 22.5% were unaffected, 33.5% had sluggish or increased opening and 44% stomatal closure. The beneficial effect of N on root development was lost at higher O 3 treatments whilst the effects of increasing O 3 on root biomass became more pronounced as N increased. Both responses to gradual changes in pollutants and climate and those under extreme weather events require further study. [ABSTRACT FROM AUTHOR]

Four genotypes of snap bean ( Phaseolus vulgaris L.) were selected to study the effects of ambient ozone concentration at a cropland area around Beijing by using 450 ppm of ethylenediurea (EDU) as a chemical protectant. During the growing season, the 8 h (9:00–17:00) average ozone concentration was very high, approximately 71.3 ppb, and AOT40 was 29.0 ppm.h. All genotypes showed foliar injury, but ozone-sensitive genotypes exhibited much more injury than ozone-tolerant ones. Compared with control, EDU significantly alleviated foliar injury, increased photosynthesis rate and chlorophyll a fluorescence, Vc max and J max , and seed and pod weights in ozone-sensitive genotypes but not in ozone-tolerant genotypes. EDU did not significantly affect antioxidant contents in any of the genotypes. Therefore, EDU effectively protected sensitive genotypes from ambient ozone damage, while protection on ozone-tolerant genotypes was limited. EDU can be regarded as a useful tool in risk assessment of ambient ozone on food security. [ABSTRACT FROM AUTHOR]

Impacts of tropospheric ozone on sweet potato (Ipomoea batatas) are poorly understood despite being a staple food grown in locations deemed at risk from ozone pollution. Three varieties of sweet potato were exposed to ozone treatments (peaks of: 30 (Low), 80 (Medium), and 110 (High) ppb) using heated solardomes. Weekly measurements of stomatal conductance (gs) and chlorophyll content (CI) were used to determine physiological responses, along with final yield. gs and CI were reduced with increasing ozone exposure, but effects were partially masked due to elevated leaf senescence and turnover. Yield for the Erato orange and Murasaki varieties was reduced by ∼40% and ∼50% (Medium and High ozone treatments, respectively, vs Low) whereas Beauregard yield was reduced by 58% in both. The DO 3 SE (Deposition of Ozone for Stomatal Exchange) model was parameterized for gs in response to light, temperature, vapour pressure deficit and soil water potential. Clear responses of gs to the environmental parameters were found. Yield reductions were correlated with both concentration based AOT40 (accumulated ozone above a threshold of 40 ppb) and flux based POD 6 (accumulated stomatal flux of ozone above a threshold of 6 nmol m− 2 s− 1) metrics (R2 0.66 p = 0.01; and R2 0.44 p = 0.05, respectively). A critical level estimate of a POD 6 of 3 (mmol m−2 Projected Leaf Area−1) was obtained using the relationship. This study showed that sweet potato yield was reduced by ozone pollution, and that stomatal conductance and chlorophyll content were also affected. Results from this study can improve model predictions of ozone impacts on sweet potato together with associated ozone risk assessments for tropical countries. [Display omitted] • Leaf stomatal conductance and chlorophyll reduced with higher ozone (O 3) exposures. • Elevated O 3 up to 110 ppb reduced yields by ∼50% in three varieties. • O 3 flux model (DO 3 SE) parametrised for sweet potato. • Critical level (at 5% yield loss) estimated using the O 3 dose/response relationship. • Results can improve risk assessments of O 3 yield impacts for this staple food crop. [ABSTRACT FROM AUTHOR]

Abstract: Two mesotrophic grassland species, Ranunculus acris and Dactylis glomerata were exposed to a range of ozone treatments (16.2–89.5 ppb 24 h mean) and two watering regimes under naturally fluctuating photosynthetically active radiation (PAR), vapour pressure deficit (VPD) and temperature. Stomatal conductance was measured throughout the experiments, and the combined data set (>1000 measurements) was analysed for effects of low and high ozone on responses to environmental stimuli. We show that when D. glomerata and R. acris were grown in 72.6–89.5 ppb ozone the stomata consistently lose the ability to respond, or have reduced response, to naturally fluctuating environmental conditions in comparison to their response in low ozone. The maximum stomatal conductance (g max) was also significantly higher in the high ozone treatment for D. glomerata. We discuss the hypotheses for the reduced sensitivity of stomatal closure to a changing environment and the associated implications for ozone flux modelling. [Copyright &y& Elsevier]