Ambient CO2 Concentration Research Articles

Chloroplast redox state mediates the short-term regulation of leaf isoprene emission.

Isoprene emission from plants not only confers thermoprotection, but also has profound impacts on atmospheric chemistry and the climate. Leaf isoprene emission is dynamically regulated in response to various environmental cues, but the exact mechanism remains unclear. It has been proposed that chloroplast redox/energy state or cytosolic phosphoenolpyruvate carboxylation regulates isoprene biosynthesis and consequently emission, and the latter has been disproven by recent literature. However, the possible covariation of chloroplast redox/energy state and cytosolic PEP carboxylation in previous experiments impedes the independent examination of the former hypothesis. We developed an index of chloroplast redox state and showed its validity by examining the relationships between the index and the rates of certain processes which have been demonstrated to be affected or unaffected by chloroplast redox/energy state. According to the former hypothesis alone, we modelled how isoprene emission rate (IER) responded to different short-term environmental variations, and compared theoretical predictions with experimental data. We predicted that no matter which environmental factor was varied, IER would respond to the index of chloroplast redox state with similar velocities. We found that IER showed comparable increasing rates in response to the increase in the index of chloroplast redox state caused by different environmental variations (0.0479, 0.0439 or 0.0319 when ambient CO2 concentration, photosynthetic photon flux density or leaf temperature was varied, respectively). These results support that chloroplast redox/energy state regulates isoprene biosynthesis, leading to dynamic isoprene emission in nature.

Incorporating Diurnal and Meter-Scale Variations of Ambient CO2 Concentrations in Development of Direct Air Capture Technologies.

To be implemented on climate-relevant scales, direct air capture of CO2 (DAC) will require large capital-intensive facilities and careful attention to cost minimization. In making decisions among potential sites for DAC facilities, all of the factors that will impact process cost and efficiency should be considered. In this paper we focus on a factor that has previously received little attention in the DAC community, namely variations in atmospheric conditions on hourly time scales and length scales of meters. We present data curated from extensive previous studies of biosphere-atmosphere fluxes with observations of CO2 concentration, temperature, and relative humidity (RH) with hourly resolution from many sites in North America. These include locations where typical diurnal variations in CO2 concentration during summer months exceeds 150 ppm. These variations are larger than the seasonal variations that exist between averaged CO2 concentrations in winter and summer, and they are highly correlated with diurnal variations in temperature and RH. Diurnal variations are dependent on the height above ground at which CO2 concentrations are measured, with smaller variations existing at heights of 10 m or more than at ground level. We illustrate the potential implications of these short-term variations for the operation and optimization of a DAC process with process-level calculations for a specific adsorption-based process using amine-rich adsorbents.

Elevated CO2 Concentration Extends Reproductive Growth Period and Enhances Carbon Metabolism in Wheat Exposed to Increased Temperature.

Both elevated atmospheric CO2 concentration ([CO2]) and increased temperature exert notable influences on wheat (Triticum aestivum L.) growth and productivity when examined individually. Nevertheless, limited research comprehensively investigates the combined effects of both factors. Winter wheat was grown in environment-controlled chambers under two concentrations of CO2 (ambient CO2 concentration and ambient CO2 concentration plus 200 µmol mol-1) and two levels of temperature (ambient temperature and ambient temperature plus 2°C). The phenology, photosynthesis, carbohydrate and nitrogen metabolism, yield and quality responses of wheat were investigated. Elevated [CO2] did not counteract warming-induced shortening of wheat phenological period but prolonged grain filling. Even though photosynthetic adaptation occurred during the reproductive growth period, elevated [CO2] still significantly enhanced carbohydrate accumulation under warming, particularly at the grain filling stage, thereby increasing yield by 20.1% compared with the ambient control. However, elevated [CO2] inhibited nitrogen assimilation at the grain filling stage under increased temperature by downregulating the expression levels of TaNR, TaNIR, TaGS1 and TaGOGAT and reducing glutamine synthetase activity, which directly led to a significant decrease of 19.4% in grain protein content relative to the ambient control. These findings suggest that elevated [CO2] will likely increase yield but decrease grain nutritional quality for wheat under future global warming scenarios.

Carbon Isotopic Composition Reflects Intrinsic Water Use Efficiency But Not its Component Traits in Sugarcane

Water is the most important resource in plant growth and is a major limiting factor in sugarcane productivity worldwide. Improving water use efficiency (WUE) can increase sugarcane productivity relative to available water resources by increasing photosynthetic capacity relative to transpiration and stomatal conductance instead of decreasing stomatal conductance. Leaf carbon stable isotopic composition (δ13Cleaf) can serve as a proxy for intrinsic WUE (WUEi) because WUEi and δ13Cleaf are theoretically related through the link between intracellular and ambient CO2 concentrations (Ci/Ca) and leaf CO2 discrimination (Δ13Cleaf). In this study we surveyed 55 sugarcane genotypes for WUEi, leaf WUE (WUEleaf), Ci/Ca, and δ13Cleaf by gas exchange measurements and stable isotope analysis. We hypothesized that significant genotypic variation was found in WUEi, WUEleaf, and δ13Cleaf within the sugarcane population in Louisiana. We also hypothesized that both WUEi and δ13Cleaf and Δ13Cleaf and Ci/Ca were correlated and that δ13Cleaf could be used as a proxy for WUEi in sugarcane. Here WUEi and WUEleaf had a genetic effect and were controlled mostly by water loss (stomatal conductance or transpiration). WUEi, WUEleaf, Ci/Ca, and δ13Cleaf were correlated, but δ13Cleaf was not correlated with the component traits of WUEi (photosynthetic rate and stomatal conductance). δ13Cleaf shows promise as a proxy for WUEi to at least be able to select the tails of the distribution, but the relationship between WUEi and δ13Cleaf may not be sufficiently strong to select WUE at a finer scale.

Impacts of Elevated CO2 and a Nitrogen Supply on the Growth of Faba Beans (Vicia faba L.) and the Nitrogen-Related Soil Bacterial Community.

Ecosystems that experience elevated CO2 (eCO2) are crucial interfaces where intricate interactions between plants and microbes occur. This study addressed the impact of eCO2 and a N supply on faba bean (Vicia faba L.) growth and the soil microbial community in auto-controlled growth chambers. In doing so, two ambient CO2 concentrations (aCO2, daytime/nighttime = 410/460 ppm; eCO2, 550/610 ppm) and two N supplement levels (without a N supply-N0-and 100 mg N as urea per kg of soil-N100) were applied. The results indicated that eCO2 mitigated the inhibitory effects of a N deficiency on legume photosynthesis and affected the CO2 assimilation efficiency, in addition to causing reduced nodulation. While the N addition counteracted the reductions in the N concentrations across the faba beans' aboveground and belowground plant tissues under eCO2, the CO2 concentrations did not significantly alter the soil NH4+-N or NO3--N responses to a N supply. Notably, under both aCO2 and eCO2, a N supply significantly increased the relative abundance of Nitrososphaeraceae and Nitrosomonadaceae, while eCO2 specifically reduced the Rhizobiaceae abundance with no significant changes under aCO2. A redundancy analysis (RDA) highlighted that the soil pH (p < 0.01) had the most important influence on the soil microbial community. Co-occurrence networks indicated that the eCO2 conditions mitigated the impact of a N supply on the reduced structural complexity of the soil microbial communities. These findings suggest that a combination of eCO2 and a N supply to crops can provide potential benefits for managing future climate change impacts on crop production.

Effects of elevated CO2 and temperature on the performance of a diet specialized neotropical herbivore and its host plant

AbstractLittle is known about the potential responses of ecologically specialized tropical species to atmospheric change and global warming. In 2 years of greenhouse experiments simulating climate change impacts, we quantified the effects of mean ambient temperature, elevated temperature (Te), current ambient CO2 concentration ([CO2]a), and doubled CO2 concentration ([CO2]e) on biomass, growth rate, and foliar chemistry of the morning glory vine, Camonea umbellata. In addition, we measured the impacts of climate change simulations on the performance and survival of the tortoise beetle, Acromis sparsa, which feeds exclusively on C. umbellata. Full‐sib A. sparsa larval broods were divided into cohorts. Each cohort was placed in one of four temperature‐CO2 controlled chambers and fed leaves grown in their respective treatments. Vines growing in [CO2]e more than doubled their biomass and their leaves expanded faster. The [CO2]a and Te treatments interacted to yield the greatest foliar [C]. Vines in [CO2]e and Te had the greatest C:N ratios, the lowest availability of nitrogen, and highest larval mortality. Whereas pupae were smaller and suffered lower survival in Te, pupal mass and survival increased in both the [CO2]e and Te treatments. Overall, the simultaneous elevation of both [CO2] and temperature caused declines in host quality, larval survivorship, and pupal mortality that were not observed when only one climate factor was altered. Based on this first tropical experimental study, we predict that C. umbellata will benefit from elevation of temperature and atmospheric [CO2] by altering its foliar chemistry to the detriment of its diet‐specialized herbivore enemy.Abstract in Spanish is available with online material.

Elevated CO2 and Nitrogen Supply Boost N Use Efficiency and Wheat (T. aestivum cv. Yunmai) Growth and Differentiate Soil Microbial Communities Related to Ammonia Oxidization.

Elevated CO2 levels (eCO2) pose challenges to wheat (Triticum aestivum L.) growth, potentially leading to a decline in quality and productivity. This study addresses the effects of two ambient CO2 concentrations (aCO2, daytime/nighttime = 410/450 ± 30 ppm and eCO2, 550/600 ± 30 ppm) and two nitrogen (N) supplements (without N supply-N0 and with 100 mg N supply as urea per kg soil-N100) on wheat (T. aestivum cv. Yunmai) growth, N accumulation, and soil microbial communities related to ammonia oxidization. The data showed that the N supply effectively mitigated the negative impacts of eCO2 on wheat growth by reducing intercellular CO2 concentrations while enhancing photosynthesis parameters. Notably, the N supply significantly increased N concentrations in wheat tissues and biomass production, thereby boosting N accumulation in seeds, shoots, and roots. eCO2 increased the agronomic efficiency of applied N (AEN) and the physiological efficiency of applied N (PEN) under N supply. Plant tissue N concentrations and accumulations are positively related to plant biomass production and soil NO3--N. Additionally, the N supply increased the richness and evenness of the soil microbial community, particularly Nitrososphaeraceae, Nitrosospira, and Nitrosomonas, which responded differently to N availability under both aCO2 and eCO2. These results underscore the importance and complexity of optimizing N supply and eCO2 for enhancing crop tissue N accumulation and yield production as well as activating nitrification-related microbial activities for soil inorganic N availability under future global environment change scenarios.

CDK8 of the mediator kinase module connects leaf development to the establishment of correct stomata patterning by regulating the levels of the transcription factor SPEECHLESS (SPCH).

The components of the mediator kinase module are highly conserved across all eukaryotic lineages, and cyclin-dependent kinase 8 (CDK8) is essential for correct cell proliferation and differentiation in diverse eukaryotic systems. We show that CDK8 couples leaf development with the establishment of correct stomata patterning for prevailing CO2 conditions. In Arabidopsis, the basic helix-loop-helix(bHLH) transcription factor SPEECHLESS(SPCH) controls cellular entry into the stomatal cell lineage, and CDK8 interacts with and phosphorylates SPCH, controlling SPCH protein levels and thereby also expression of the SPCH target genes encoding key regulators of cell fate and asymmetric cell divisions. The lack of the CDK8-mediated control of SPCH results in an increased number of meristemoid and guard mother cells, and increased stomata index in the cdk8 mutants. Increasing atmospheric CO2 concentrations trigger a developmental programme controlling cell entry into stomatal lineage by limiting the asymmetric divisions. In cdk8, the number of meristemoids and guard mother cells remains the same under ambient and high CO2 concentrations, as the accumulated levels of SPCH caused by the lack of CDK8 appear to override the negative regulation of increased CO2. Thus, our work provides novel mechanistic understanding of how plants alter critical leaf properties in response to increasing atmospheric CO2.

Theory and tests for coordination among hydraulic and photosynthetic traits in co-occurring woody species.

Co-occurring plants show wide variation in their hydraulic and photosynthetic traits. Here, we extended 'least-cost' optimality theory to derive predictions for how variation in key hydraulic traits potentially affects the cost of acquiring and using water in photosynthesis and how this, in turn, should drive variation in photosynthetic traits. We tested these ideas across 18 woody species at a temperate woodland in eastern Australia, focusing on hydraulic traits representing different aspects of plant water balance, that is storage (sapwood capacitance, CS), demand vs supply (branch leaf : sapwood area ratio, AL : AS and leaf : sapwood mass ratio and ML : MS), access to soil water (proxied by predawn leaf water potential, ΨPD) and physical strength (sapwood density, WD). Species with higher AL : AS had higher ratio of leaf-internal to ambient CO2 concentration during photosynthesis (ci : ca), a trait central to the least-cost theory framework. CS and the daily operating range of tissue water potential (∆Ψ) had an interactive effect on ci : ca. CS, WD and ΨPD were significantly correlated with each other. These results, along with those from multivariate analyses, underscored the pivotal role leaf : sapwood allocation (AL : AS), and water storage (CS) play in coordination between plant hydraulic and photosynthetic systems. This study uniquely explored the role of hydraulic traits in predicting species-specific photosynthetic variation based on optimality theory and highlights important mechanistic links within the plant carbon-water balance.

Rare earth elements as a tool to study the foliar nutrient uptake phenomenon under ambient and elevated atmospheric CO2 concentration

The ability of plants to uptake nutrients from mineral dust lying on their foliage may prove to be an important mechanism by which plants will cope with increasing CO2 levels in the atmosphere. This mechanism had only recently been reported and was shown to compensate for the projected dilution in plants ionome. However, this phenomenon has yet to be thoroughly studied, particularly in terms of the expected trends under different dust types and varying atmospheric CO2 concentrations, as projected by the IPCC. We treated plants grown under ambient (415 ppm) and elevated CO2 (850 ppm) conditions with either desert dust, volcanic ash, and fire ash analogues by applying it solely on plant foliage and studied their Rare Earth Elements concentrations and patterns. The Rare Earth Elements compositions of the treated plants originated from the dust application, and their incorporation into the plants led to a significant increase in plants vitality, evident in increased photosynthetic activity and biomass. Two trends in the foliar nutrient uptake mechanism were revealed by the Rare Earth Elements, one is that different treatments affected the plant in decreasing order volcanic ash > desert dust > fire ash. The second trend is that foliar intake becomes more significant under elevated CO2, an observation not previously seen. This testifies that the use of Rare Earth Elements in the study of foliar nutrient uptake, and other biological mechanisms is fundamental, and that foliar pathways of nutrient uptake will indeed become more dominant with increasing CO2 under expected atmospheric changes.

Leaf economics spectrum of wheat in response to multigenerational atmospheric elevated CO2

While numerous studies have explored the impacts of elevated atmospheric CO2 concentration (e[CO2]) on leaf traits in plants within a single life cycle, the effects of multigenerational e[CO2] on leaf functional traits and their interrelationships remain obscure in major crops. Leaf economics spectrum (LES) comprises a group of leaf traits, which describes trade-offs between the leaf characteristics that reflect carbon economy or returns on the investments of nutrients and dry mass. In this study, the wheat seeds harvested from a 7-generation experiment under the e[CO2] (800 μmol L−1) or the ambient CO2 concentration were planted to assess changes in the LES. Our results revealed a consistent increase in mass-normalized leaf nitrogen and phosphorus concentration under the e[CO2] over the generations. Photosynthetic phosphorus use efficiency was positively correlated with photosynthetic rate per unit mass, dark respiration per unit mass, photosynthetic rate per unit area, leaf phosphorus per unit area, and dark respiration per unit area. Moreover, we used structural equation model to illustrate the network of relationships among LES traits and shoot dry weight, providing insights into the effects of the multigenerational e[CO2] on wheat growth. This study contributes novel perspectives to our understandings of wheat responses to long-term climate change.

Multigenerational Effects of Elevated CO2 and N Supply on Leaf Gas Exchange Traits in Wheat Plants

ABSTRACTThe responses of leaf gas exchange of wheat (Triticum aestivum L.) to elevated atmospheric CO2 concentration (e[CO2]) were often investigated within a single generation, while the long‐term acclimation of photosynthesis to growth in e[CO2] over multiple generations has not been systematically studied. Here, five wheat cultivars were grown under either ambient (a[CO2], 400 ppm) or elevated (e[CO2], 800 ppm) CO2 concentration for three consecutive generations (G1 to G3) with two N‐fertilisation levels (1N–1 g N pot−1 and 2N–2 g N pot−1) in climate‐controlled greenhouses. Leaf gas exchange was determined in each generation of plants under different treatments. It was found that at both N levels, e[CO2] stimulated photosynthetic rate while reducing stomatal conductance, transpiration rate and leaf N concentration, resulting in an enhanced water use efficiency and photosynthetic N use efficiency. The N level modulated the intergenerational responses of photosynthetic capacity to e[CO2]; under low N supply, the maximum carboxylation rate (Vcmax), the maximum electron transport rate (Jmax) and the rate of triose phosphate utilisation (TPU) were significantly downregulated by e[CO2] from the first to the second generation, but recovered in the third generation; whereas at high N levels, photosynthetic acclimation was diminished with the progress of generations, with Vcmax, Jmax and TPU increased under e[CO2] in the third generation. These results suggest that intergenerational adaptation could alleviate the e[CO2]‐induced reduction of the photosynthetic capacity, but plants with different N status responded differently to adapt to the long‐term exposure to e[CO2]. Among the five cultivars, 325Jimai showed a better photosynthetic performance under e[CO2] over the three generations, while 02‐1Shiluan appeared to be more inhibited by CO2 elevation in the long term conditions. These findings provide new insights for breeding strategies in the future CO2‐enriched environments.

Performance Evaluation of Three Peanut Cultivars Grown under Elevated CO2 Concentrations

This study explored the performance and physiological responses of three commercially used peanut cultivars in Australian farming systems under ambient and elevated CO2 conditions, aiming to identify the most suitable genotype for dual-purpose (grain and graze) cropping experiments. The experiment utilized an open-top chamber (OTC) facility to regulate CO2 concentrations. The elevated CO2 (EC) treatment targeted approximately 650 ± 50 µmol mol−1, while both ambient CO2 (AC) and control plots operated at a concentration of approximately 400 µmol mol−1. Notably, control plots without chambers served as a reference for current CO2 and environmental conditions. In contrast, despite having the same ambient CO2 concentration, AC plots were enclosed in chambers, allowing for plant growth comparisons with EC plots with the same environmental conditions aside from CO2 levels. The analyses revealed significant effects of CO2 enrichment on peanut plants. In particular, the EC treatment led to enhanced photosynthetic rates (20% in Kairi, 31% in Holt, and 19% in Alloway), alongside reduced stomatal conductance (−55% in Kairi, −32% in Holt, and −40% in Alloway), transpiration, and increased water use efficiency compared to AC conditions. Elevated CO2 levels positively influenced pod yields in Kairi (+41%) and Alloway (+36%). However, CO2 enrichment did not significantly alter the protein content, total phenolic content, cupric-reducing antioxidant capacity, and ferric-reducing antioxidant power of peanut plant material. Furthermore, no significant differences were observed in the phytochemical composition among the three cultivars under ambient or elevated CO2 conditions. On the other hand, analysis of the fibre structure conducted on peanut stover harvested at plant maturity suggested potential declines in feedstock quality. Based on the findings of this research, further investigations and testing, including simulated grazing trials, will be carried out to identify a single breed line suitable for dual-purpose management under future elevated CO2 conditions.

Drought Has a Greater Negative Effect on the Growth of the C3Chenopodium quinoa Crop Halophyte than Elevated CO2 and/or High Temperature.

Plant growth and productivity are predicted to be affected by rising CO2 concentrations, drought and temperature stress. The C3 crop model in a changing climate is Chenopodium quinoa Willd-a protein-rich pseudohalphyte (Amaranthaceae). Morphophysiological, biochemical and molecular genetic studies were performed on quinoa grown at ambient (400 ppm, aCO2) and elevated (800 ppm, eCO2) CO2 concentrations, drought (D) and/or high temperature (eT) treatments. Among the single factors, drought caused the greatest stress response, inducing disturbances in the light and dark photosynthesis reactions (PSII, apparent photosynthesis) and increasing oxidative stress (MDA). Futhermore, compensation mechanisms played an important protective role against eT or eCO2. The disruption of the PSII function was accompanied by the activation of the expression of PGR5, a gene of PSI cyclic electron transport (CET). Wherein under these conditions, the constant Rubisco content was maintained due to an increase in its biosynthesis, which was confirmed by the activation of rbcL gene expression. In addition, the combined stress treatments D+eT and eCO2+D+eT caused the greatest negative effect, as measured by increased oxidative stress, decreased water use efficiency, and the functioning of protective mechanisms, such as photorespiration and the activity of antioxidant enzymes. Furthermore, decreased PSII efficiency and increased non-photochemical quenching (NPQ) were not accompanied by the activation of protective mechanisms involving PSI CET. In summary, results show that the greatest stress experienced by C. quinoa plants was caused by drought and the combined stresses D+eT and eCO2+D+eT. Thus, drought consistently played a decisive role, leading to increased oxidative stress and a decrease in defense mechanism effectiveness.

Ocean acidification alters microeukaryotic and bacterial food web interactions in a eutrophic subtropical mesocosm

Ocean acidification (OA) is known to influence biological and ecological processes, mainly focusing on its impacts on single species, but little has been documented on how OA may alter plankton community interactions. Here, we conducted a mesocosm experiment with ambient (∼410 ppmv) and high (1000 ppmv) CO2 concentrations in a subtropical eutrophic region of the East China Sea and examined the community dynamics of microeukaryotes, bacterioplankton and microeukaryote-attached bacteria in the enclosed coastal seawater. The OA treatment with elevated CO2 affected taxa as the phytoplankton bloom stages progressed, with a 72.89% decrease in relative abundance of the protist Cercozoa on day 10 and a 322% increase in relative abundance of Stramenopile dominated by diatoms, accompanied by a 29.54% decrease in relative abundance of attached Alphaproteobacteria on day 28. Our study revealed that protozoans with different prey preferences had differing sensitivity to high CO2, and attached bacteria were more significantly affected by high CO2 compared to bacterioplankton. Our findings indicate that high CO2 changed the co-occurrence network complexity and stability of microeukaryotes more than those of bacteria. Furthermore, high CO2 was found to alter the proportions of potential interactions between phytoplankton and their predators, as well as microeukaryotes and their attached bacteria in the networks. The changes in the relative abundances and interactions of microeukaryotes between their predators in response to high CO2 revealed in our study suggest that high CO2 may have profound impacts on marine food webs.

Exploring natural genetic diversity in a bread wheat multi-founder population: dual imaging of photosynthesis and stomatal kinetics.

Recent research has shown that optimizing photosynthetic and stomatal traits holds promise for improved crop performance. However, standard phenotyping tools such as gas exchange systems have limited throughput. In this work, a novel approach based on a bespoke gas exchange chamber allowing combined measurement of the quantum yield of PSII (Fq'/Fm'), with an estimation of stomatal conductance via thermal imaging was used to phenotype a range of bread wheat (Triticum aestivum L.) genotypes. Using the dual-imaging methods and traditional approaches, we found broad and significant variation in key traits, including photosynthetic CO2 uptake at saturating light and ambient CO2 concentration (Asat), photosynthetic CO2 uptake at saturating light and elevated CO2 concentration (Amax), the maximum velocity of Rubisco for carboxylation (Vcmax), time for stomatal opening (Ki), and leaf evaporative cooling. Anatomical analysis revealed significant variation in flag leaf adaxial stomatal density. Associations between traits highlighted significant relationships between leaf evaporative cooling, leaf stomatal conductance, and Fq'/Fm', highlighting the importance of stomatal conductance and stomatal rapidity in maintaining optimal leaf temperature for photosynthesis in wheat. Additionally, gsmin and gsmax were positively associated, indicating that potential combinations of preferable traits (i.e. inherently high gsmax, low Ki, and maintained leaf evaporative cooling) are present in wheat. This work highlights the effectiveness of thermal imaging in screening dynamic gs in a panel of wheat genotypes. The wide phenotypic variation observed suggested the presence of exploitable genetic variability in bread wheat for dynamic stomatal conductance traits and photosynthetic capacity for targeted optimization within future breeding programmes.

Elevated CO2 improves grain yield in bread wheat by enhancing carbon assimilation, activities of carbohydrate metabolic and antixidant enzymes

This study aimed to explore the effects of elevated CO2 (e[CO2]) on wheat performance under drought stress, while investigating the role of eco-physiology, carbohydrate metabolic and antioxidant enzymes to predict the grain yield. Wheat genotype Lianmai6 was grown under ambient (400 ppm) and elevated (800 ppm) CO2 concentrations, with subsequent exposure to drought stress prior to anthesis. Leaf parameters, including photosynthetic rate (An), stomatal conductance (Gs), and transpiration rate (E), were significantly declined under drought. Grain yield parameters were adversely affected by drought stress, while An with water use efficiency (WUE) and yield traits increased under e[CO2]. Notably, the activities of certain carbohydrate metabolic enzymes were increased in sink tissues but reduced significantly in source tissues under drought conditions. However, activities phosphoglucomutase (PGM and phophoglucoisomerase (PGI) were increased in source tissues under the combined effect of drought and e[CO2]. Total antioxidant potential (TAP) decreased in both leaf and spike under drought conditions, yet increased significantly under e[CO2]. These findings suggest that e[CO2] can enhance CO2 assimilation by boosting antioxidant potential and facilitate increased supply of photosynthates through enhanced activities of various carbohydrate metabolic enzymes, ultimately the better grain yield. These findings could elucidate the partial mechanism of better grain yield in bread wheat under combined effect of e[CO2] and drought stress.

Partitioning urban forest evapotranspiration based on integrating eddy covariance of water vapor and carbon dioxide fluxes

Partitioning of evapotranspiration (ET) in urban forest lands plays a vital role in mitigating ambient temperature and evaluating the effects of urbanization on the urban hydrological cycle. While ET partitioning has been extensively studied in diverse natural ecosystems, there remains a significant paucity of research on urban ecosystems. The flux variance similarity (FVS) theory is used to partition urban forest ET into soil evaporation (E) and vegetation transpiration (T). This involves measurements from eddy covariance of water vapor and carbon dioxide fluxes, along with an estimated leaf-level water use efficiency (WUE) algorithm. The study compares five WUE algorithms in partitioning the average transpiration fraction (T/ET) and validates the results using two years of oxygen isotope observations. Although all five FVS-based WUE algorithms effectively capture the dynamic changes in hourly scale T and E across the four seasons, the algorithm that assumes a constant ratio of intercellular CO2 concentration (ci) to ambient CO2 concentration (ca) provides the most accurate simulation results for the ratio of T/ET. The performance metrics for this specific algorithm include the RMSE of 0.06, R2 of 0.88, the bias of 0.02, and MAPE of 8.9 %, respectively. Comparing urban forests to natural forests, the T/ET in urban areas is approximately 2.4–25.3 % higher, possibly due to the elevated air temperature (Ta), greater leaf area index (LAI), and increased soil water availability. Correlation analysis reveals that the T/ET dynamic is primarily controlled by Ta, LAI, net radiation, ca, and soil water content at half-hourly, daily, and monthly scales. This research provides valuable insights into the performance and applicability of various WUE algorithms in urban forests, contributing significantly to understanding the impact of urbanization on energy, water, and carbon cycles within ecosystems.

Tripartite interactions of an endophytic entomopathogenic fungus, Asian corn borer, and host maize under elevated carbon dioxide.

Biological control of insect pests is encountering an unprecedented challenge in agricultural systems due to the ongoing rise in carbon dioxide (CO2) level. The use of entomopathogenic fungi (EPF) in these systems is gaining increased attention, and EPF as crop endophytes hold the potential for combining insect pest control and yield enhancement of crops, but the effects of increased CO2 concentration on this interaction are poorly understood. Here, the introduction of endophytic EPF was explored as an alternative sustainable management strategy benefiting crops under elevated CO2, using maize (Zea mays), Asian corn borer (Ostrinia furnacalis), and EPF (Beauveria bassiana) to test changes in damage to maize plants from O. furnacalis, and the nutritional status (content of carbon, nitrogen, phosphorus, potassium), biomass, and yield of maize. The results showed that endophytic B. bassiana could alleviate the damage caused by O. furnacalis larvae for maize plants under ambient CO2 concentration, and this effect was enhanced under higher CO2 concentration. Inoculation with B. bassiana effectively counteracted the adverse impact of elevated CO2 on maize plants by preserving the nitrogen content at its baseline level (comparable with ambient CO2 conditions without B. bassiana). Both simultaneous effects could explain the improvement of biomass and yield of maize under B. bassiana inoculation and elevated CO2. This finding provides key information about the multifaceted benefits of B. bassiana as a maize endophyte. Our results highlight the promising potential of incorporating EPF as endophytes into integrated pest management strategies, particularly under elevated CO2 concentrations. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Ambient carbon dioxide concentration correlates with SARS-CoV-2 aerostability and infection risk

An improved understanding of the underlying physicochemical properties of respiratory aerosol that influence viral infectivity may open new avenues to mitigate the transmission of respiratory diseases such as COVID-19. Previous studies have shown that an increase in the pH of respiratory aerosols following generation due to changes in the gas-particle partitioning of pH buffering bicarbonate ions and carbon dioxide is a significant factor in reducing SARS-CoV-2 infectivity. We show here that a significant increase in SARS-CoV-2 aerostability results from a moderate increase in the atmospheric carbon dioxide concentration (e.g. 800 ppm), an effect that is more marked than that observed for changes in relative humidity. We model the likelihood of COVID-19 transmission on the ambient concentration of CO2, concluding that even this moderate increase in CO2 concentration results in a significant increase in overall risk. These observations confirm the critical importance of ventilation and maintaining low CO2 concentrations in indoor environments for mitigating disease transmission. Moreover, the correlation of increased CO2 concentration with viral aerostability need to be better understood when considering the consequences of increases in ambient CO2 levels in our atmosphere.