CO2 dose-response functions for wheat grain, protein and mineral yield based on FACE and open-top chamber experiments

Influence of Mycorrhiza on C:N:P Stoichiometry in Senesced Leaves

Senesced leaves play a vital role in nutrient cycles in the terrestrial ecosystem. The carbon (C), nitrogen (N) and phosphorus (P) stoichiometries in senesced leaves have been reported, which are influenced by biotic and abiotic factors, such as climate variables and plant functional groups. It is well known that mycorrhizal types are one of the most important functional characteristics of plants that affect leaf C:N:P stoichiometry. While green leaves' traits have been widely reported based on the different mycorrhiza types, the senesced leaves' C:N:P stoichiometries among mycorrhizal types are rarely investigated. Here, the patterns in senesced leaves' C:N:P stoichiometry among plants associated with arbuscular mycorrhizal (AM), ectomycorrhizal (ECM), or AM + ECM fungi were explored. Overall, the senesced leaves' C, with 446.8 mg/g in AM plants, was significantly lower than that in AM + ECM and ECM species, being 493.1 and 501.4 mg/g, respectively, which was mainly caused by boreal biomes. The 8.9 mg/g senesced leaves' N in ECM plants was significantly lower than in AM (10.4 mg/g) or AM + ECM taxa (10.9 mg/g). Meanwhile, the senesced leaves' P presented no difference in plant associations with AM, AM + ECM and ECM. The senesced leaves' C and N presented contrary trends with the changes in mean annual temperature (MAT) and mean annual precipitation (MAP) in ECM or AM + ECM plants. The differences in senesced leaves' C and N may be more easily influenced by the plant mycorrhizal types, but not P and stoichiometric ratios of C, N and P. Our results suggest that senesced leaves' C:N:P stoichiometries depend on mycorrhizal types, which supports the hypothesis that mycorrhizal type is linked to the evolution of carbon-nutrient cycle interactions in the ecosystem.

Impact of climate change on wheat grain composition and quality

Wheat grain quality, an important determinant for human nutrition, is often overlooked when improving crop production for stressed environments. Climate change makes this task more difficult by imposing combined stresses. The scenarios relevant to climate change include elevated CO₂ concentrations (eCO₂ ) and extreme climatic events such as drought, heat waves, and salinity stresses. However, data on wheat quality in terms of climate change are limited, with no concerted efforts at the global level to provide an equitable and consistent climate risk assessment for wheat grain quality. Climate change induces changes in the quality and composition of wheat grain, a premier staple food crop globally. Climate-change events, such as eCO₂ , heat, drought, salinity stress stresses, heat + drought, eCO₂  + drought, and eCO₂  + heat stresses, alter wheat grain quality in terms of grain weight, nutrient, anti-nutrient, fiber, and protein content and composition, starch granules, and free amino acid composition. Interestingly, in comparison with other stresses, heat stress and drought stress increase phytate content, which restricts the bioavailability of essential mineral elements. All climatic events, except for eCO₂  + heat stress, increase grain gliadin content in different wheat varieties. However, grain quality components depend more on inter-varietal difference, stress type, and exposure time and intensity. The climatic events show differential regulation of protein and starch accumulation, and mineral metabolism in wheat grains. Rapid climate shifting impairs wheat productivity and causes grain quality to deteriorate by interrupting the allocation of essential nutrients and photoassimilates. © 2022 Society of Chemical Industry.

Changes in per capita wheat production in China in the context of climate change and population growth

To address challenges associated with climate change, population growth and decline in international trade linked to the COVID-19 pandemic, determining whether national crop production can meet populations' requirements and contribute to socio-economic resilience is crucial. Three crop models and three global climate models were used in conjunction with predicted population changes. Compared with wheat production in 2000-2010, total production and per capita wheat production were significantly (P < 0.05) increase in 2020-2030, 2030-2040 and 2040-2050, respectively, under RCP4.5 and RCP8.5 due to climate change in China. However, when considering population and climate changes, the predicted per capita production values were 125.3 ± 0.3, 127.1 ± 2.3 and 128.8 ± 2.7 kg during the 2020-2030, 2030-2040, 2040-2050 periods under RCP4.5, or 126.2 ± 0.7, 128.7 ± 2.5, and 131.0 ± 4.1 kg, respectively, under RCP8.5. These values do not significantly differ (P > 0.05) from the baseline level (127.9 ± 1.3 kg). The average per capita production in Loess Plateau and Gansu-Xinjiang subregions declined. In contrast, per capita production in the Huanghuai, Southwestern China, and Middle-Lower Yangtze Valleys subregions increased. The results suggest that climate change will increase total wheat production in China, but population change will partly offset the benefits to the grain market. In addition, domestic grain trade will be influenced by both climate and population changes. Wheat supply capacity will decline in the main supply areas. Further research is required to address effects of the changes on more crops and in more countries to obtain deeper understanding of the implications of climate change and population growth for global food production and assist formulation of robust policies to enhance food security.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12571-023-01351-x.

Interactive effect of elevated CO2 and nitrogen dose reprograms grain ionome and associated gene expression in bread wheat

Wheat crop grown under elevated CO₂ (EC) often have a lowered grain nitrogen (N) and protein concentration along with an altered grain ionome. The mechanistic understanding on the impact of CO₂ x N interactions on the grain ionome and the expression of genes regulating grain ionome is scarce in wheat. In the present study, the interactive effect of EC and N dosage on grain yield, grain protein, grain ionome, tissue nitrate, and the expression of genes contributing to grain ionome (TaNAM-B1 and TaYSL6) are described. Three bread wheat genotypes were evaluated under two CO₂ levels (Ambient CO₂ (AC) of 400 ± 10 ppm and elevated CO₂ (EC) of 700 ± 10 ppm) and two N levels (Low (LN) and Optimum N (ON). In EC, wheat genotypes HD2967 and HI 1500 recorded a significant decrease in grain nitrate content, while leaf and stem nitrate showed a significant increase. BT. Schomburgk (BTS), showed a significant increase in unassimilated nitrate and a decline in grain N and grain protein under EC. There was a general decline of grain ionome (N, P, K, Ca, Fe) in EC, except for grain Na content. The expression of genes TaNAM-B1 and TaYSL6 associated with protein and micronutrient remobilization to grains during senescence were affected by both EC and N treatments. For instance, in flag leaves of BTS, the expression of TaNAM-B1 and TaYSL6 were lower in EC-LN compared to AC-LN. In maturing spikes, transcript abundance of TaNAM-B1 and TaYSL6 were lower in EC in BTS. The altered transcript abundance of TaYSL6 and TaNAM-B1 in source and sink supports the change in grain ionome and suggests an N dependent transcriptional reprogramming in EC.

Relationship between endophytic microbial diversity and grain quality in wheat exposed to multi-generational CO2 elevation

To explore the potential association between the diversity of endophytic microorganisms and modifications of grain quality in wheat exposed to multi-generational elevated CO₂ concentration, the grain quality attributes and microbial diversity were tested after five generations successively grown in ambient CO₂ concentration (F5_A, 400 μmol L^-1) and elevated CO₂ concentration (F5_E, 800 μmol L^-1). Elevated CO₂ concentration significantly increased the grain number and starch concentration, while decreased the grain protein concentration. Multi-generational exposure to elevated CO₂ concentration also led to significant changes in grain amino acid concentration. In response to the elevated CO₂ concentration, Pseudomonas, Rhodococcus, Ralstonia, and Klebsiella were the dominant bacterial genera, while Penicillium, Cutaneotrichosporon, Fusarium, Sarocladium, Acremonium and Aspergillus were the dominant fungal genera in wheat grain. A significantly positive correlation was found between Pseudomonas, Penicillium and ratio of starch to protein concentration, implying that the multi-generational CO₂ elevation induced modifications in grain quality might be associated with the changes in grain microbial diversity. The results of this study suggest that the endophytic microbes may play an important role in modulating the grain nutritional quality in wheat under multi-generational e[CO₂] exposure, through regulating starch and N metabolism and production of secondary metabolites.

Climate Change, Crop Yields, and Grain Quality of C3 Cereals: A Meta-Analysis of [CO2], Temperature, and Drought Effects

Cereal yield and grain quality may be impaired by environmental factors associated with climate change. Major factors, including elevated CO2 concentration ([CO2]), elevated temperature, and drought stress, have been identified as affecting C3 crop production and quality. A meta-analysis of existing literature was performed to study the impact of these three environmental factors on the yield and nutritional traits of C3 cereals. Elevated [CO2] stimulates grain production (through larger grain numbers) and starch accumulation but negatively affects nutritional traits such as protein and mineral content. In contrast to [CO2], increased temperature and drought cause significant grain yield loss, with stronger effects observed from the latter. Elevated temperature decreases grain yield by decreasing the thousand grain weight (TGW). Nutritional quality is also negatively influenced by the changing climate, which will impact human health. Similar to drought, heat stress decreases starch content but increases grain protein and mineral concentrations. Despite the positive effect of elevated [CO2], increases to grain yield seem to be counterbalanced by heat and drought stress. Regarding grain nutritional value and within the three environmental factors, the increase in [CO2] is possibly the more detrimental to face because it will affect cereal quality independently of the region.

Climate Change, Crop Yields, and Grain Quality of C3 Cereals: A Meta-Analysis of [CO2], Temperature, and Drought Effects

Cereal yield and grain quality may be impaired by environmental factors associated with climate change. Major factors, including elevated CO₂ concentration ([CO₂]), elevated temperature, and drought stress, have been identified as affecting C₃ crop production and quality. A meta-analysis of existing literature was performed to study the impact of these three environmental factors on the yield and nutritional traits of C₃ cereals. Elevated [CO₂] stimulates grain production (through larger grain numbers) and starch accumulation but negatively affects nutritional traits such as protein and mineral content. In contrast to [CO₂], increased temperature and drought cause significant grain yield loss, with stronger effects observed from the latter. Elevated temperature decreases grain yield by decreasing the thousand grain weight (TGW). Nutritional quality is also negatively influenced by the changing climate, which will impact human health. Similar to drought, heat stress decreases starch content but increases grain protein and mineral concentrations. Despite the positive effect of elevated [CO₂], increases to grain yield seem to be counterbalanced by heat and drought stress. Regarding grain nutritional value and within the three environmental factors, the increase in [CO₂] is possibly the more detrimental to face because it will affect cereal quality independently of the region.

Genotypic Variability on Grain Yield and Grain Nutritional Quality Characteristics of Wheat Grown under Elevated CO2 and High Temperature

The progressive rise in atmospheric CO2 concentrations and temperature associated with climate change is predicted to have a major impact on the productivity and quality of food crops. Therefore, food security is highly dependent on climate change. Following a survey with 60 bread wheat genotypes, here we investigated the genetic variation in grain yield and nutritional quality among 10 of these genotypes grown under elevated CO2 and temperature. With this purpose, the biomass production, grain yield-related traits, the grain concentration of starch, total protein, phenolic compounds, and mineral nutrients, together with the total antioxidant capacity, were determined. Variation among genotypes was found for almost all the studied traits. Higher grain and ear numbers were associated with increased grain yield but decreased grain total protein concentration and minerals such as Cu, Fe, Mg, Na, P, and Zn. Mineral nutrients were mainly associated with wheat biomass, whereas protein concentration was affected by plant biomass and yield-related traits. Associations among different nutrients and promising nutrient concentrations in some wheat genotypes were also found. This study demonstrates that the exploration of genetic diversity is a powerful approach, not only for selecting genotypes with improved quality, but also for dissecting the effect of the environment on grain yield and nutritional composition.

The da1 mutation in wheat increases grain size under ambient and elevated CO2 but not grain yield due to trade-off between grain size and grain number

Grain size is potentially yield determining in wheat, controlled by the ubiquitin pathway and negatively regulated by ubiquitin receptor DA1. We analyzed whether increased thousand grain weight in wheat da1 mutant is translated into higher grain yield and whether additional carbon provided by elevated (e)CO2 can be better used by the da1, displaying higher grain sink strength and size. Yield-related, biomass, grain quality traits, and grain dimensions were analyzed by two-factorial mixed-model analysis, regarding genotype and eCO2. da1 increased grain size but reduced spikes and grains per plant, grains per spike, and spikelets per spike, independent of eCO2 treatment, leaving total grain yield unchanged. eCO2 increased yield and grain number additively and independently of da1 but did not overcome the trade-off between grain size and number observed for da1. eCO2 but not da1 impaired grain quality, strongly decreasing concentrations of several macroelement and microelement. In conclusion, intrinsic stimulation of grain sink strength and grain size, achieved by da1, is not benefitting total yield unless trade-offs between grain size and numbers can be overcome. The results reveal interactions of yield components in da1-wheat under ambient and eCO2, thereby uncovering limitations enhancing wheat yield potential.

The main effects of elevated CO2 and soil-water deficiency on 1H NMR-based metabolic fingerprints of Coffea arabica beans by factorial and mixture design

The metabolic response of Coffea arabica trees in the face of the rising atmospheric concentration of carbon dioxide (CO₂) combined with the reduction in soil-water availability is complex due to the various (bio)chemical feedbacks. Modern analytical tools and the experimental advance of agronomic science tend to advance in the understanding of the metabolic complexity of plants. In this work, Coffea arabica trees were grown in a Free-Air Carbon Dioxide Enrichment dispositive under factorial design (2²) conditions considering two CO₂ levels and two soil-water availabilities. The ¹H NMR mixture design-fingerprinting effects of CO₂ and soil-water levels on beans were strategically investigated using the principal component analysis (PCA), analysis of variance (ANOVA) - simultaneous component analysis (ASCA) and partial least squares-discriminant analysis (PLS-DA). From the ASCA, the CO₂ factor had a significant effect on changing the ¹H NMR profile of fingerprints. The soil-water factor and interaction (CO₂ × soil-water) were not significant. ¹H NMR fingerprints with PCA, ASCA and PLS-DA analysis determined spectral profiles for fatty acids, caffeine, trigonelline and glucose increases in beans from current CO₂, while quinic acid/chlorogenic acids, malic acid and kahweol/cafestol increased in coffee beans from elevated CO₂. PLS-DA results revealed a good classification performance between the significant effect of the atmospheric CO₂ levels on the fingerprints, regardless of the soil-water availabilities. Finally, the PLS-DA model showed good prediction ability, successfully classifying validation data-set of coffee beans collected over the vertical profile of the plants and included several fingerprints of different extracting solvents. The results of this investigation suggest that the association of experimental design, mixture design, PCA, ASCA and PLS-DA can provide accurate information on a series of metabolic changes provoked by climate changes in products of commercial importance, in addition to minimizing the extra work necessary in classic analytical approaches, encouraging the development of similar strategies.

The effects of elevated CO2 and elevated O3 exposure on plant growth, yield and quality of grains of two wheat cultivars grown in north India

Global food security is challenged by increasing levels of CO₂, O₃ and temperature trough their impacts on production and grain quality of wheat, one of the major C₃ crops and staple food across the world. The present study was conducted to assess the effects of elevated levels of CO₂ (EC; 550 ppm) and tropospheric O₃ (EO; 70 ppb) as well as of combined interactive treatment [EC X EO; ECO] on plant growth, yield and grain quality of two wheat cultivars (HD-2967 and C-306) grown during 2016-17 and 2017-18 using free air ozone and carbon dioxide enrichment (FAOCE) facility under field conditions. Individually, EC, increased leaf area index (LAI; 15.9-28.2%), photosynthetic rate (Pn; 11.4-20.3%) and yield (8.2-20.9%) whereas EO declined LAI (5.1-12.5%), Pn (2.8-11.8%) and yield (2.2-14.2%) over ambient conditions (Amb: 405.2 ppm CO₂ and 30.7 ppb O₃). Under ECO condition, EC increased LAI (2.2-17.1%), Pn (2.8-17.6%) and grain yield parameters (4.4-24.3%) across the cultivars in both years, but reduced the positive effects of EO on quality as compared to Amb. Dilution effect of increased yield under EC condition have reduced total protein, micro- and macro-nutrient concentrations whereas EO increased them notably compared to Amb. Starch in grains increased under EC but reduced under EO as compared to Amb. AOT40, the sum of averaged difference of O₃ h^-1 concentration beyond 40 ppb for 7 hours (31233 ppb h^-1) in FAOCEs rings during the crop growth period led to reduction in average grain yield of HD-2967 and C-306 by 11.6 and 8.5% or by 1.6 and 1.3% yield loss per ppb increase of O₃, respectively. The growth, yield and quality parameters of both wheat cultivars responded similarly but to different extent to all treatments. EC was able to offset the negative effects of EO on yield and yield components only, but not those concerning the quality of grains. To stabilize global food security, precursor gases forming tropospheric ozone must be constrained.

Metabolic Effects of Elevated CO2 on Wheat Grain Development and Composition

The increase in the atmospheric CO₂ concentration is predicted to influence wheat production and grain quality and nutritional properties. In the present study, durum wheat (Triticum durum Desf. cv. Sula) was grown under two different CO₂ (400 versus 700 μmol mol^-1) concentrations to examine effects on the crop yield and grain quality at different phenological stages (from grain filling to maturity). Exposure to elevated CO₂ significantly increased aboveground biomass and grain yield components. Growth at elevated CO₂ diminished the elemental N content as well as protein and free amino acids, with a typical decrease in glutamine, which is the most represented amino acid in grain proteins. Such a general decrease in nitrogenous compounds was associated with altered kinetics of protein accumulation, N remobilization, and N partitioning. Our results highlight important modifications of grain metabolism that have implications for its nutritional quality.

Effects of elevated CO2 on plant C-N-P stoichiometry in terrestrial ecosystems: A meta-analysis

A substantial number of experiments have so far been carried out to study the response of the C-N-P stoichiometry of terrestrial plants to the rising CO₂ level of the earth. However, there is a need of systematic evaluation for assessing the impact of the elevated CO₂ on plant C-N-P stoichiometry. In the present investigation, a comprehensive meta-analysis involving 386 published reports and including 4481 observations has been carried out. The goal of the research was to determine the response of plants to their C-N-P stoichiometry due to elevated levels of global atmospheric CO₂. The results showed that rising CO₂ altered the concentration of C (+2.19%, P < 0.05), N (-9.73%, P < 0.001) and P (-3.23%, P < 0.001) and C:N (+13.29%, P < 0.001) and N:P ratios (-7.32%, P < 0.0001). Overall, a slightly increasing trend in the C:P ratio (P > 0.05) in the plant was observed. However, plant leaf, shoot and herbaceous type of plants showed more sensitivity to rising CO₂. CO₂ magnitude exhibited a positive effect (P < 0.05) on C:N ratio. Additionally, "CO₂ acclimation" hypothesis as proposed by the authors of the current paper was also tested in the study. Results obtained, especially, show changes of C and N concentrations and C:P ratio to an obvious down-regulation for long-term CO₂ fumigation. At spatial scales, a reduction of plant N concentration was found to be higher in the southern hemisphere. The CO₂ enrichment methods affected the plant C-N-P stoichiometry. Compared to FACE (free-air CO₂ enrichment), OTC (open top chamber) showed larger changes of C, N, P, and N:P. The results of the present study should, therefore, become helpful to offer a better understanding towards the response of the terrestrial plant C-N-P stoichiometry to an elevated global atmospheric CO₂ in the future.

The relationship between transpiration and nutrient uptake in wheat changes under elevated atmospheric CO2

The impact of elevated [CO₂ ] (e[CO₂ ]) on crops often includes a decrease in their nutrient concentrations where reduced transpiration-driven mass flow of nutrients has been suggested to play a role. We used two independent approaches, a free-air CO₂ enrichment (FACE) experiment in the South Eastern wheat belt of Australia and a simulation study employing the agricultural production systems simulator (APSIM), to show that transpiration (mm) and nutrient uptake (g m^-2 ) of nitrogen (N), potassium (K), sulfur (S), calcium (Ca), magnesium (Mg) and manganese (Mn) in wheat are correlated under e[CO₂ ], but that nutrient uptake per unit water transpired is higher under e[CO₂ ] than under ambient [CO₂ ] (a[CO₂ ]). This result suggests that transpiration-driven mass flow of nutrients contributes to decreases in nutrient concentrations under e[CO₂ ], but cannot solely explain the overall decline.

Grain yield and quality responses of wheat expressing a barley sucrose transporter to combined climate change factors

Crop yield stability must be ensured under future climate conditions such as elevated CO2 and high temperatures. We tested 'HOSUT', a winter wheat line expressing a grain-targeted sucrose transporter of barley in response to combinations of CO2 enrichment, a heat wave, and high nitrogen fertilization. Compared with wild-type Certo, HOSUT had a superior performance for grain yield, aboveground biomass, and ears per plant, obviously due to transgene activity in developing grains and young vegetative sinks. HOSUT grains were larger and contained more endosperm cells. HOSUT and high CO2 effects similarly improved phenological and yield-related traits. Significant HOSUT-CO2 interactions for biomass of stems, ears, grain yield, nitrogen yield, and grain number revealed that Certo was promoted by CO2 enrichment, whereas HOSUT responded weakly. CO2 enrichment strongly reduced and HOSUT effects weakly reduced grain nitrogen, storage proteins, and free amino acids. In contrast to CO2 enrichment, HOSUT effects did not impair grain micronutrient concentrations. Significant HOSUT-nitrogen fertilization interactions for ear biomass, grain yield, grain number per plant, and harvest index indicated that HOSUT benefited more from additional nitrogen. The heat wave decreased aboveground and ear biomass, grain yield, harvest index, grain size, and starch and water use, but increased grain sucrose concentration.

Inorganic nitrogen form: a major player in wheat and Arabidopsis responses to elevated CO2

Critical for predicting the future of primary productivity is a better understanding of plant responses to rising atmospheric carbon dioxide (CO2) concentration. This review considers recent results on the role of the inorganic nitrogen (N) forms nitrate (NO3-) and ammonium (NH4+) in determining the responses of wheat and Arabidopsis to elevated atmospheric CO2 concentration. Here, we identify four key issues: (i) the possibility that different plant species respond similarly to elevated CO2 if one accounts for the N form that they are using; (ii) the major influence that plant-soil N interactions have on plant responses to elevated CO2; (iii) the observation that elevated CO2 may favor the uptake of one N form over others; and (iv) the finding that plants receiving NH4+ nutrition respond more positively to elevated CO2 than those receiving NO3- nutrition because elevated CO2 inhibits the assimilation of NO3- in shoots of C3 plants. We conclude that the form and amount of N available to plants from the rhizosphere and plant preferences for the different N forms are essential for predicting plant responses to elevated CO2.

Nutrient constraints on terrestrial carbon fixation: The role of nitrogen

Carbon dioxide (CO₂) concentrations in the earth's atmosphere are projected to rise from current levels near 400ppm to over 700ppm by the end of the 21st century. Projections over this time frame must take into account the increases in total net primary production (NPP) expected from terrestrial plants, which result from elevated CO₂ (eCO₂) and have the potential to mitigate the impact of anthropogenic CO₂ emissions. However, a growing body of evidence indicates that limitations in soil nutrients, particularly nitrogen (N), the soil nutrient most limiting to plant growth, may greatly constrain future carbon fixation. Here, we review recent studies about the relationships between soil N supply, plant N nutrition, and carbon fixation in higher plants under eCO₂, highlighting key discoveries made in the field, particularly from free-air CO₂ enrichment (FACE) technology, and relate these findings to physiological and ecological mechanisms.

Increasing CO2 differentially affects essential and non-essential amino acid concentration of rice grains grown in cadmium-contaminated soils

Environmental pollution by both ambient CO2 and heavy metals has been steadily increasing, but we do not know how fluctuating CO2 concentrations influence plant nutrients under high Cd pollution, especially in crops. Here, we studied the effects of elevated CO2 and Cd accumulation on proteins and amino acids in rice under Cd stress. In this pot experiment, we analyzed the amino-acid profile of 20 rice cultivars that accumulate Cd differently; the plants were grown in Cd-containing soils under ambient conditions and elevated CO2 levels. We found that although Cd concentrations appeared to be higher in most cultivars under elevated CO2 than under ambient CO2, the effect was significant only in seven cultivars. Combined exposure to Cd and elevated CO2 strongly decreased rice protein and amino acid profiles, including essential and non-essential amino acids. Under elevated CO2, the ratios of specific amino acids were either higher or lower than the optimal ratios provided by FAO/WHO, suggesting that CO2 may flatten the overall amino-acid profile, leading to an excess in some amino acids and deficiencies in others when the rice is consumed. Thus, Cd-tainted rice limits the concentration of essential amino acids in rice-based diets, and the combination with elevated CO2 further exacerbates the problem.

Soil warming enhances the hidden shift of elemental stoichiometry by elevated CO2 in wheat

Increase in atmospheric CO2 concentration ([CO2]) and associated soil warming along with global climate change are expected to have large impacts on grain mineral nutrition in wheat. The effects of CO2 elevation (700 μmol l(-1)) and soil warming (+2.4 °C) on K, Ca and Mg concentrations in the xylem sap and their partitioning in different organs of wheat plant during grain filling were investigated. Results showed that the combination of elevated [CO2] and soil warming improved wheat grain yield, but decreased plant K, Ca and Mg accumulation and their concentrations in the leaves, stems, roots and grains. The reduced grain mineral concentration was attributed to the lowered mineral uptake as exemplified by both the decreased stomatal conductance and mineral concentration in the xylem sap. These findings suggest that future higher atmospheric [CO2] and warmer soil conditions may decrease the dietary availability of minerals from wheat crops. Breeding wheat cultivars possessing higher ability of mineral uptake at reduced xylem flux in exposure to climate change should be a target.

Temperature determines size and direction of effects of elevated CO2 and nitrogen form on yield quantity and quality of Chinese cabbage

Rising atmospheric CO2 concentrations (e[CO2 ]) are presumed to have a significant impact on plant growth and yield and also on mineral nutrient composition, and therefore, on nutritional quality of crops and vegetables. To assess the relevance of these effects in future agroecosystems it is important to understand how e[CO2 ] interacts with other environmental factors. In the present study, we examined the interactive effects of e[CO2 ] with temperature and the form in which nitrogen is supplied (nitrate or ammonium nitrate) on growth, amino acid content and mineral nutrient composition of Chinese cabbage (Brassica pekinensis Rupr.), a crop characterised by its high nutritional value and increasing relevance for human nutrition in many developing countries. Higher temperature, ammonium nitrate and e[CO2 ] had a positive impact on net photosynthesis and growth. A stimulating effect of e[CO2 ] on growth was only observed if the temperature was high (21/18 °C, day/night), and an interaction of e[CO2 ] with N form was only observed if the temperature was ambient (15/12 °C, day/night). Mineral nutrient composition was affected in a complex manner by all three factors and their interaction. These results demonstrate how much the effect of e[CO2 ] on mineral quality of crops depends on other environmental factors. Changes in temperature, adapting N fertilisation and the oxidation state of N have the potential to counteract the mineral depletion caused by e[CO2 ].

Expression patterns of C- and N-metabolism related genes in wheat are changed during senescence under elevated CO2 in dry-land agriculture

Projected climatic impacts on crop yield and quality, and increased demands for production, require targeted research to optimise nutrition of crop plants. For wheat, post-anthesis carbon and nitrogen remobilisation from vegetative plant parts and translocation to grains directly affects grain carbon (C), nitrogen (N) and protein levels. We analysed the influence of increased atmospheric CO2 on the expression of genes involved in senescence, leaf carbohydrate and nitrogen metabolism and assimilate transport in wheat under field conditions (Australian Grains Free Air CO2 Enrichment; AGFACE) over a time course from anthesis to maturity, the key period for grain filling. Wheat grown under CO2 enrichment had lower N concentrations and a tendency towards greater C/N ratios. A general acceleration of the senescence process by elevated CO2 was not confirmed. The expression patterns of genes involved in carbohydrate metabolism, nitrate reduction and metabolite transport differed between CO2 treatments, and this CO2 effect was different between pre-senescence and during senescence. The results suggest up-regulation of N remobilisation and down-regulation of C remobilisation during senescence under elevated CO2, which is consistent with greater grain N-sink strength of developing grains.