Elevated atmospheric [CO2] (e[CO2]) may alleviate the effects of water stress on plants. It is unclear however whether this results exclusively from changes in stomatal conductance and water savings or also reflects changes in metabolic pathways triggered by the extra carbohydrate supplies under e[CO2]. To help address this knowledge gap, metabolite patterns were analysed in leaves and nodules of lentils grown in a Free-Air CO2 Enrichment facility in a water limited agro-ecosystem over the course of two contrasting growing seasons, one with high (well above average), and one with low (well below average) rainfall. Metabolomic analyses of tissues sampled at flowering showed contrasting responses to e[CO2] in the contrasting seasons. In the high rainfall season, e[CO2] was associated with more pronounced signatures of active energy and amino acid metabolism in leaves as well as in nodules, and particularly increased abundance of proteinogenic amino acids in leaves and nodules, which suggested strong stimulation of nodule N2-fixation and N supply to leaves. In the low rainfall season, e[CO2] was associated with high abundance of stress responsive metabolites, including putative osmoprotectants such as sugars and polyols as well as some N-containing compounds (proline, gamma-aminobutyric acid, putrescine), while the concentration of proteinogenic amino acids in leaves was reduced. In nodules, e[CO2] was linked to lower concentrations of sugars, polyols and most proteinogenic amino acids, along with higher concentrations of N-containing stress metabolites. However, there was little evidence that e[CO2] enhanced energy and amino acid metabolism in the low rainfall season. This study suggests that e[CO2] amplifies rather than mitigates the effect of different seasons on lentil metabolism. Whilst in a high rainfall season e[CO2] intensified metabolic patterns related to active growth and N-fixation, in a low rainfall season e[CO2] strengthened stress response signatures.

Context Elevated atmospheric CO2 (e[CO2]) and nitrogen (N) fertilisation stimulate biomass and yield of crops. However, their interactions depend on crop growth stages and may affect water use dynamics.Aims and methods This study investigated the interactive effects of two N rates, 0 and 100kgNha−1, and two CO2 concentrations, ambient (a[CO2], ~400μmolmol−1) and e[CO2] (~550μmolmol−1), on biomass, yield and water use of two wheat cultivars, Wyalkatchem (N-use efficient) and Yitpi (local), using a free air CO2 enrichment facility.Key results Elevated [CO2] stimulated leaf area (10%, P=0.003) and aboveground biomass (11%, P=0.03). In addition, e[CO2] reduced stomatal conductance (25%, P<0.001) and increased net assimilation rates (12%, P<0.001), resulting in greater (40%, P<0.001) intrinsic water use efficiency. During early growth stages, e[CO2] resulted in higher water use than a[CO2]; however, this difference disappeared later in the season, resulting in similar cumulative water use under both CO2 concentrations. Supplemental N stimulated grain yield of Yitpi by 14% while decreasing that of Wyalkatchem by 7% (N×cultivar, P=0.063). With supplemental N, Yitpi maintained greater post-anthesis leaf N, chlorophyll content, canopy cover and net assimilation rate than Wyalkatchem.Conclusions During early growth stages, the e[CO2]-induced stimulation of leaf-level water use efficiency was offset by greater biomass, resulting in higher water use. By the end of the season, similar cumulative water use under both CO2 concentrations indicates the dominating effect of the prevailing seasonal conditions in the study area. Observed yield responses of the studied cultivars to supplemental N were associated with their ability to maintain post-anthesis photosynthetic capabilities.Implications Our findings suggest that N-use efficiency traits and responsiveness need to be considered independently to optimise benefits from the ‘CO2 fertilisation effect’ through breeding.

To investigate the interactive effects of elevated CO 2 and heat stress (HS), we grew two contrasting wheat cultivars, early-maturing Scout and high-tillering Yitpi, under non-limiting water and nutrients at ambient (aCO 2 , 450 ppm) or elevated (eCO 2 , 650 ppm) CO 2 and 22°C in the glasshouse. Plants were exposed to two 3-day HS cycles at the vegetative (38.1°C) and/or flowering (33.5°C) stage. At aCO 2 , both wheat cultivars showed similar responses of photosynthesis and mesophyll conductance to temperature and produced similar grain yield. Relative to aCO 2 , eCO 2 enhanced photosynthesis rate and reduced stomatal conductance and maximal carboxylation rate ( V cmax ). During HS, high temperature stimulated photosynthesis at eCO 2 in both cultivars, while eCO 2 stimulated photosynthesis in Scout. Electron transport rate ( J max ) was unaffected by any treatment. eCO 2 equally enhanced biomass and grain yield of both cultivars in control, but not HS, plants. HS reduced biomass and yield of Scout at eCO 2 . Yitpi, the cultivar with higher grain nitrogen, underwent a trade-off between grain yield and nitrogen. In conclusion, eCO 2 improved photosynthesis of control and HS wheat, and improved biomass and grain yield of control plants only. Under well-watered conditions, HS was not detrimental to photosynthesis or growth but precluded a yield response to eCO 2 . Key message High temperatures increased photosynthetic rates only at eCO 2 and photosynthesis was upregulated after recovery from heat stress at eCO 2 in Scout suggesting that eCO 2 increased optimum temperature of photosynthesis.

Climate change impacts to crop production are likely to be greatest in semi-arid regions already constrained by marginal growing conditions. The response of temperate grain crops (wheat, field pea and lentil) to elevated CO2 (eCO(2)) (550 mu mol mol(-1)) under semi-arid field conditions was studied over 11 years in the Australian Grains Free Air CO2 Enrichment (AGFACE) research program. This review synthesizes key outcomes and implications for crop adaptation in a semi-arid environment. Across all crops and environments, eCO(2) increased mean yields (16-58%) compared to current ambient (aCO(2)) concentrations. Wheat yields increased by 18% and 29% under rainfed and supplemental irrigation, respectively resulting in yield increases of 6.1 (aCO(2)) and 14.1 (eCO(2)) kgha(-1) mm(-1) of additional water. Wheat grain [N] declined (similar to 7%) under eCO(2) across cultivars, resulting in reduced grain protein and bread baking quality, and this was not reversed by additional fertilizer N. Of several tested crop traits favorable for dryland cropping of wheat under eCO(2), a transpiration efficiency trait increased yields under eCO(2) representing a path for adaptation in semi-arid environments. The rates and amounts of N-2 fixation in legumes were increased by eCO(2) but were greater under higher soil water content. Barley yellow dwarf virus incidence increased by 10.6% due to changes in epidemiology under eCO(2). Results from AGFACE suggest that maximizing the advantages of eCO(2) requires synergistic development of adapted management systems, innovative genetics and removing physiological bottlenecks. This systems approach will increase the potential to maintain agricultural production in new combinations of environments for longer than if changes are piecemeal.

Atmospheric carbon dioxide concentrations [CO2] are increasing steadily. Some reports have shown that root growth in grain crops is mostly stimulated in the topsoil rather than evenly throughout the soil profile by e[CO2], which is not optimal for crops grown in semi-arid environments with strong reliance on stored water. An experiment was conducted during the 2014 and 2015 growing seasons with two lentil (Lens culinaris) genotypes grown under Free Air CO2 Enrichment (FACE) in which root growth was observed non-destructively with mini-rhizotrons approximately every 2–3 weeks. Root growth was not always statistically increased by e[CO2] and not consistently between depths and genotypes. In 2014, root growth in the top 15 cm of the soil profile (topsoil) was indeed increased by e[CO2], but increases at lower depths (30–45 cm) later in the season were greater than in the topsoil. In 2015, e[CO2] only increased root length in the topsoil for one genotype, potentially reflecting the lack of plant available soil water between 30–60 cm until recharged by irrigation during grain filling. Our limited data to compare responses to e[CO2] showed that root length increases in the topsoil were correlated with a lower yield response to e[CO2]. The increase in yield response was rather correlated with increases in root growth below 30 cm depth.

We compared Support Vector Machine (SVM) and Random Forest (RF) machine learning approaches with the widely used Jarvis-type phenomenological model for predicting stomatal conductance (g(s)) in wheat (Triticum aestivum L.) using historical measurements collected in the Australian Grains Free-Air CO2 Enrichment (AGFACE) facility. The machine learning-based methods produced greater accuracy than the Jarvis-type model in predicting gs from leaf age, atmospheric [CO2], photosynthetically active radiation, vapour pressure deficit, temperature, time of day, and soil water availability (i.e. phenological and environmental variables determining gs). The R-2 was 0.76 for the Jarvis-type but 0.92 for SVM and 0.97 for RF machine learning-based models, with a calculated RMSE of 0.292 mol m(-2) s(-1) in the Jarvis-type compared to 0.129 mol m(-2) s(-1) in SVM and 0.081 mol m(-2) s(-1) in RF. The machine learning models, however, needed large datasets for training to achieve statistical significance, and do not offer the same opportunity to provide physiological insights through a statistically testable hypothesis. These results show that using the machine-learning based methods can achieve high prediction accuracy of gs that is especially important when incorporated into larger models, but their ability to extrapolate beyond observed data ranges will need to be assessed before they could be considered in place of the physical model.

Summary Photosynthetic stimulation by elevated [CO2] (e[CO2]) may be limited by the capacity of sink organs to use photosynthates. In many legumes, N2‐fixing symbionts in root nodules provide an additional sink, so that legumes may be better able to profit from e[CO2]. However, drought not only constrains photosynthesis but also the size and activity of sinks, and little is known about the interaction of e[CO2] and drought on carbon sink strength of nodules and other organs. To compare carbon sink strength, faba bean was grown under ambient (400 ppm) or elevated (700 ppm) atmospheric [CO2] and subjected to well‐watered or drought treatments, and then exposed to 13C pulse‐labelling using custom‐built chambers to track the fate of new photosynthates. Drought decreased 13C uptake and nodule sink strength, and this effect was even greater under e[CO2], and was associated with an accumulation of amino acids in nodules. This resulted in decreased N2 fixation, and increased accumulation of new photosynthates (13C/sugars) in leaves, which in turn can feed back on photosynthesis. Our study suggests that nodule C sink activity is key to avoid sink limitation in legumes under e[CO2], and legumes may only be able to achieve greater C gain if nodule activity is maintained.

Reducing the number of tillers per plant using a tiller inhibition (tin) gene has been considered as an important trait for wheat production in dryland environments. We used a spatial analysis approach with a daily time-step coupled radiation and transpiration efficiency model to simulate the impact of the reduced-tillering trait on wheat yield under different climate change scenarios across Australia's arable land. Our results show a small but consistent yield advantage of the reduced-tillering trait in the most water-limited environments both under current and likely future conditions. Our climate scenarios show that whilst elevated [CO2] (e[CO2]) alone might limit the area where the reduced-tillering trait is advantageous, the most likely climate scenario of e[CO2] combined with increased temperature and reduced rainfall consistently increased the area where restricted tillering has an advantage. Whilst long-term average yield advantages were small (ranged from 31 to 51 kg ha(-1) year(-1)), across large dryland areas the value is large (potential cost-benefits ranged from Australian dollar 23 to 60 MIL/year). It seems therefore worthwhile to further explore this reduced-tillering trait in relation to a range of different environments and climates, because its benefits are likely to grow in future dry environments where wheat is grown around the world.

In 2017, the Birmingham Institute of Forest Research (BIFoR) began to conduct Free Air Carbon Dioxide Enrichment (FACE) within a mature broadleaf deciduous forest situated in the United Kingdom. BIFoR FACE employs large‐scale infrastructure, in the form of lattice towers, forming ‘arrays’ which encircle a forest plot of ~30 m diameter. BIFoR FACE consists of three treatment arrays to elevate local CO2 concentrations (e[CO2]) by +150 µmol/mol. In practice, acceptable operational enrichment (ambient [CO2] + e[CO2]) is ±20% of the set point 1‐min average target. There are a further three arrays that replicate the infrastructure and deliver ambient air as paired controls for the treatment arrays. For the first growing season with e[CO2] (April to November 2017), [CO2] measurements in treatment and control arrays show that the target concentration was successfully delivered, that is: +147 ± 21 µmol/mol (mean ± SD) or 98 ± 14% of set point enrichment target. e[CO2] treatment was accomplished for 97.7% of the scheduled operation time, with the remaining time lost due to engineering faults (0.6% of the time), CO2 supply issues (0.6%) or adverse weather conditions (1.1%). CO2 demand in the facility was driven predominantly by wind speed and the formation of the deciduous canopy. Deviations greater than 10% from the ambient baseline CO2 occurred <1% of the time in control arrays. Incidences of cross‐contamination >80 µmol/mol (i.e. >53% of the treatment increment) into control arrays accounted for <0.1% of the enrichment period. The median [CO2] values in reconstructed three‐dimensional [CO2] fields show enrichment somewhat lower than the target but still well above ambient. The data presented here provide confidence in the facility setup and can be used to guide future next‐generation forest FACE facilities built into tall and complex forest stands.

Early vigour in wheat is a trait that has received attention for its benefits reducing evaporation from the soil surface early in the season. However, with the growth enhancement common to crops grown under elevated atmospheric CO2 concentrations (e[CO2]), there is a risk that too much early growth might deplete soil water and lead to more severe terminal drought stress in environments where production relies on stored soil water content. If this is the case, the incorporation of such a trait in wheat breeding programmes might have unintended negative consequences in the future, especially in dry years. We used selected data from cultivars with proven expression of high and low early vigour from the Australian Grains Free Air CO2 Enrichment (AGFACE) facility, and complemented this analysis with simulation results from two crop growth models which differ in the modelling of leaf area development and crop water use. Grain yield responses to e[CO2] were lower in the high early vigour group compared to the low early vigour group, and although these differences were not significant, they were corroborated by simulation model results. However, the simulated lower response with high early vigour lines was not caused by an earlier or greater depletion of soil water under e[CO2] and the mechanisms responsible appear to be related to an earlier saturation of the radiation intercepted. Whether this is the case in the field needs to be further investigated. In addition, there was some evidence that the timing of the drought stress during crop growth influenced the effect of e[CO2] regardless of the early vigour trait. There is a need for FACE investigations of the value of traits for drought adaptation to be conducted under more severe drought conditions and variable timing of drought stress, a risky but necessary endeavour.

Future rapid increases in atmospheric CO2 concentration [CO2 ] are expected, with values likely to reach ~550 ppm by mid-century. This implies that every terrestrial plant will be exposed to nearly 40% more of one of the key resources determining plant growth. In this review we highlight selected areas of plant interactions with elevated [CO2 ] (e[CO2 ]), where recently published experiments challenge long-held, simplified views. Focusing on crops, especially in more extreme and variable growing conditions, we highlight uncertainties associated with four specific areas. (1) While it is long known that photosynthesis can acclimate to e[CO2 ], such acclimation is not consistently observed in field experiments. The influence of sink-source relations and nitrogen (N) limitation on acclimation is investigated and current knowledge about whether stomatal function or mesophyll conductance (gm ) acclimate independently is summarised. (2) We show how the response of N uptake to e[CO2 ] is highly variable, even for one cultivar grown within the same field site, and how decreases in N concentrations ([N]) are observed consistently. Potential mechanisms contributing to [N] decreases under e[CO2 ] are discussed and proposed solutions are addressed. (3) Based on recent results from crop field experiments in highly variable, non-irrigated, water-limited environments, we challenge the previous opinion that the relative CO2 effect is larger under drier environmental conditions. (4) Finally, we summarise how changes in growth and nutrient concentrations due to e[CO2 ] will influence relationships between crops and weeds, herbivores and pathogens in agricultural systems.

Legumes grown in Mediterranean environments frequently experience terminal drought which reduces yield and N-2 fixation processes. Decreased N-2 fixation during reproductive phases may constrain seed nitrogen concentrations ([N]), reducing protein concentration of grain legumes. Plants grown under elevated atmospheric CO2 concentrations ([CO2)) have greater water use efficiency. This may result in reduced use of conserved/ stored soil water, potentially helping to reduce soil water deficits later during grain filling. The extent that this process applies to drought sensitive grain legumes, which are extensively cultivated in Mediterranean environments is unclear. The objectives of this study were to investigate yield, N-2 fixation and seed N response of faba bean (Vicia faba L. cv. 'Fiesta') grown in a dryland Mediterranean-type environment under elevated [CO2]. Plants were grown in soil columns under ambient [COO ("400 ppm) or elevated [CO2] (e[CO2], (similar to)550 ppm) in a Free-Air CO2 Enrichment (FACE) facility in the field. One sub-group was continuously well-watered (80% field capacity, FC), whereas a second sub-group was exposed to a drought treatment (water was withheld until 30% FC was reached, which was then maintained during the reproductive phases). Biomass, gas exchange, C-13 isotopic discrimination, N-2 fixation by the natural abundance 13N method, nodulation and soil water content were assessed throughout the crop developmental stages. Initially, plants grown under elevated [CO2] depleted soil water more slowly in the drought treatment than those under ambient [CO2], but as plants grown under elevated [CO2] produced more biomass they used soil water more rapidly, especially towards the critical pod-filling phase. Water savings during the first phase of the drought treatment, through flowering up to the start of pod-filling, were associated with increased yield ( + 25%) and N-2 fixation (+15%) under drought. Elevated [CO2]-induced stimulation of nodulation and nodule density helped maintain N-2 fixation under drought, even though nodule activity decreased under the combined effect of e[CO2] and drought from pod-filling onwards. This later stage decrease was associated with decreased carbohydrate and increased amino acid concentrations in nodules, indicating a down-regulation of N-2 fixation. Associated with the decrease of N-2 fixation during pod-filling, seed N concentration was lower under the combination of e[CO2] and drought. We propose a conceptual model to explain the importance of N-2 fixation during the grain filling stage to maintain seed N concentration under e[CO2]. These findings suggest that e[CO2]induced savings in soil water may mitigate negative effects of drought on yield and N-2 fixation of faba bean, without fully compensating the effect of prolonged drought on seed N concentration.

화학공학소재연구정보센터 홈 로그인 로그아웃 연락처 사이트맵. 센터: 센터소개; 회원가입/정보수정. 뉴스: 공지사항; 연구동향; 우수연구자소개; 취업정보. 연구정보: 문헌DB; KDB; Compound Search; 전문연구정보; 동영상; 심포지움 자료; 연구성과보고서; 저널정보; 논문 작성법; 참고문헌DB; 분석기기DB; 화학공정DB; PSPDB; 연구자지식지도; 상태도정보. 교육정보: 사이버강의-학부; 사이버강의-대학원; 실무강좌; 강의자료 링크; 교육자료 링크; 사이버실험실; 물성측정실험 매뉴얼. 커뮤니티: 공학포럼; 카페; 신진연구자인터뷰. 리소스: 특허정보; 술어DB; 관련법령; 자격증정보; 성과소개서; 연구보고서. 문헌DB: 학술지 검색; 학술대회 발표논문집; 최신 국내 저널; 최신 리뷰페이퍼. KDB: Periodic Table of Elements; Unit Conversion; Universal Constants; Pure Component Properties; Binary Vapor-Liquid Equil …

The stimulatory effect of elevated [CO2 ] (e[CO2 ]) on crop production in future climates is likely to be cancelled out by predicted increases in average temperatures. This effect may become stronger through more frequent and severe heat waves, which are predicted to increase in most climate change scenarios. Whilst the growth and yield response of some legumes grown under the interactive effect of e[CO2 ] and heat waves has been studied, little is known about how N2 fixation and overall N metabolism is affected by this combination. To address these knowledge gaps, two lentil genotypes were grown under ambient [CO2 ] (a[CO2 ], ~400 µmol·mol-1 ) and e[CO2 ] (~550 µmol·mol-1 ) in the Australian Grains Free Air CO2 Enrichment facility and exposed to a simulated heat wave (3-day periods of high temperatures ~40 °C) at flat pod stage. Nodulation and concentrations of water-soluble carbohydrates (WSC), total free amino acids, N and N2 fixation were assessed following the imposition of the heat wave until crop maturity. Elevated [CO2 ] stimulated N2 fixation so that total N2 fixation in e[CO2 ]-grown plants was always higher than in a[CO2 ], non-stressed control plants. Heat wave triggered a significant decrease in active nodules and WSC concentrations, but e[CO2 ] had the opposite effect. Leaf N remobilization and grain N improved under interaction of e[CO2 ] and heat wave. These results suggested that larger WSC pools and nodulation under e[CO2 ] can support post-heat wave recovery of N2 fixation. Elevated [CO2 ]-induced accelerated leaf N remobilisation might contribute to restore grain N concentration following a heat wave.

Crop production in dryland systems is mainly dependent on water availability from rainfall which is highly variable between years and locations. We employed the widely used boundary-line analysis, with an existing industry dataset from across the Australian dryland cropping regions, to investigate the relative sensitivity of grain yield in canola (Brassica napus L.), chickpea (Cicer arietinum L.), faba bean (Vicia faba L), field pea (Pisum sativum L.), lentil (Lens culinaris L.), and narrow-leafed lupin (Lupinus angustifolius L.) to variation in rainfall totals. Chickpea had the lowest non-productive water use, was more responsive to water supply, and reached its maximum yield at a lower water supply than the other species. In contrast canola had the highest non-productive water use, was less responsive to water supply, and reached its maximum yield at a higher water supply than the other species. These results suggest that chickpea offers the most stable outcome, and canola the greatest variation, in response to the variability in rainfall totals between years and locations.

Increasing atmospheric carbon dioxide concentration ([CO2]) stimulates the leaf-level (intrinsic) water use efficiency (iWUE), which may mitigate the adverse effects of drought by lowering water use in plants. This study investigated the interactive effect of [CO2] and soil type on growth, yield and water use of canola (Brassica napus L.) in a dryland environment.

Elevated atmospheric CO2 concentration (e[CO2]) can stimulate the photosynthesis and productivity of C3 species including food and forest crops. Intraspecific variation in responsiveness to e[CO2] can be exploited to increase productivity under e[CO2]. However, active selection of genotypes to increase productivity under e[CO2] is rarely performed across a wide range of germplasm, because of constraints of space and the cost of CO2 fumigation facilities. If we are to capitalise on recent advances in whole genome sequencing, approaches are required to help overcome these issues of space and cost. Here, we discuss the advantage of applying prescreening as a tool in large genome×e[CO2] experiments, where a surrogate for e[CO2] was used to select cultivars for more detailed analysis under e[CO2] conditions. We discuss why phenotypic prescreening in population-wide screening for e[CO2] responsiveness is necessary, what approaches could be used for prescreening for e[CO2] responsiveness, and how the data can be used to improve genetic selection of high-performing cultivars. We do this within the framework of understanding the strengths and limitations of genotype-phenotype mapping.

Legume N2 fixation is highly sensitive to drought. Elevated [CO2] (e[CO2]) decreases stomatal conductance (gs) and improves water use efficiency (WUE), which may result in soil water conservation and allow N2 fixation to continue longer under drought. Using a Free-Air CO2 Enrichment (FACE) approach, this study aimed to elucidate whether e[CO2] improves N2 fixation of Pisum sativum L. under drought.

An Amendment to this paper has been published and can be accessed via a link at the top of the paper.