Increasing CO2 Concentration Research Articles

Asymmetric ENSO teleconnections in a symmetric CO2 concentration pathway

Abstract El Niño-Southern Oscillation (ENSO) is the strongest interannual phenomenon occurring in the tropical Pacific, significantly affecting the entire world. The ENSO response to increasing CO2 concentrations have been extensively studied, but the reverse scenario is still not well understood. Here, we investigate the hysteresis of ENSO teleconnections in a CO2 removal simulation of an earth system model. During the ramp-up period of CO2 concentrations, Pacific-North American and Pacific-South American patterns are intensified, with the eastward shift of their poles, which are even further intensified during the ramp-down period. This ENSO teleconnection hysteresis is closely linked to the tropical-origin hysteresis, in which, during the ramp-down periods, the prevalence of the eastern-Pacific type El Niño leads to the hysteresis in the eastern Hemispheric ENSO teleconnections and the enhanced ENSO skewness and the eastward shift of ENSO-induced tropical atmospheric convection do to that in the western Hemispheric ENSO teleconnection. The alterations by the tropical origin are predominantly associated with intensified southward migration of the Intertropical Convergence Zone, along with a stronger El Niño-like warming trend. We also demonstrate that the hysteretic change in the mid-latitude mean state over the North Pacific region could lead to hysteresis of the ENSO teleconnection without invoking a tropical origin.

Numerical simulation of fluidized bed reactor for calcium looping energy release process in thermochemical storage: Influence of key conditions

The thermochemical energy storage technology applied to concentrating solar power is expected to realize the large-scale deployment of solar power. Reactor design is recognized as a key challenge. In this study, the calcium looping energy release process in a bubbling fluidized bed reactor was numerically simulated using an Eulerian-Eulerian Two-fluid Model. The effects of immersed tubes, particle size, CO2 concentration, and flow velocity on the multi-physical coupling characteristics during the carbonation process were explored. The result indicated that the presence of immersed tubes improves flow characteristics and effectively controls the bed temperature. Particle size had no significant effect on the carbonation process during the kinetically controlled stage. Increasing CO2 concentration significantly enhanced the conversion rate; however, it could lead to a reduction in particle renewal frequency, thereby deteriorating the heat transfer coefficient (HTC). The study on flow velocity indicated that a balance should be struck between bed stability and reaction conversion rate, with the model identifying 0.48 m/s to 0.74 m/s as the suitable operating gas velocity. Additionally, the study compared two methods for calculating HTC and analyzed the energy utilization efficiency during the carbonation process, providing recommendations for industrial applications.

The Attribution of February Extremes over North America: A Forecast-Based Storyline Study

Abstract The importance of extreme event attribution rises as climate change causes severe damage to populations resulting from unprecedented events. In February 2019, a planetary wave shifted along the U.S.–Canadian border, simultaneously leading to troughing with anomalous cold events and ridging over Alaska and northern Canada with abnormal warm events. Also, a dry-stabilized anticyclonic circulation over low latitudes induced warm extreme events over Mexico and Florida. Most attribution studies compare the climate model simulations under natural or actual forcing conditions and assess probabilistically from a climatological point of view. However, in this study, we use multiple ensembles from an operational forecast model, promising statistical as well as dynamically constrained attribution assessment, often referred to as the storyline approach to extreme event attribution. In the globally averaged results, increasing CO2 concentrations lead to distinct warming signals at the surface, resulting mainly from diabatic heating. Our study finds that CO2-induced warming eventually affects the possibility of extreme events in North America, quantifying the impact of anthropogenic forcing over less than a week’s forecast simulation. Our study assesses the validity of the storyline approach conditional on the forecast lead times, which is hindered by rising noise in CO2 signals and the declining performance of the forecast model. The forecast-based storyline approach is valid for at least half of the land area within a 6-day lead time before the target extreme occurrence. Our attribution results highlight the importance of achieving net-zero emissions ahead of schedule to reduce the occurrence of severe heatwaves.

Exploring the nexus of grain production and climate variability under nitrogen and hydrothermal regimes using CERES-wheat model

Field experiment was conducted at Punjab Agricultural University, Bathinda from 2017-18 to 2019-20 to evaluate the growth and yield of wheat under varying sowing dates (Nov. 15, Nov. 30 & Dec 15), irrigation regimes (IW: CP = 0.6, 0.8, & 1.0), and nitrogen levels 80% RDN, RDN & 120% RDN). Timely sowing (15 November) resulted in significantly highest grain yield (5090 kg ha-1) and delay in sowing caused reduction in yield by 2.83 % and 9.91 % in crop sown on 30 November and 15 December respectively. Yield and yield attributes were found to increase with increase in irrigation and nitrogen levels. The highest yield was achieved with 15 November sowing, IW: CPE ratio 1.0 and 120% RDN. The sensitivity of the validated CERES-wheat model to increase in temperature by 0.7, 1.2, 1.5 0C and CO2 concentration by 435, 460, 500 ppm, as projected for years 2030, 2040 and 2050 respectively, revealed reduction in the wheat yield. The combination of 15 November sown crop, irrigation at IW:CPE ratio 1.0, and recommended dose of nitrogen showed resilience against increasing CO2 concentration and temperature rise.

Improved water use efficiency of vegetation due to carbon fertilization not translating to increased soil moisture in India

Soil moisture (SM) plays a critical role in land–atmosphere interaction. Literature shows that the CO2 fertilization effect (CFE) governs vegetation dynamics and its interactions with the atmosphere. However, the impacts of changing vegetation properties due to CFE, on SM, specifically in India, remains unexplored. Comparing Land-hist (observed CO2 concentration) and Land-cCO2 (constant preindustrial CO2 concentration) simulations with the same meteorological forcings from the Land Use Model Inter-comparison Project (LUMIP), we found that changing vegetation due to CFE impacts SM following two pathways. Enhanced water use efficiency (WUE) due to CFE seeks to ameliorate SM by regulating transpiration. Conversely, elevated CO2 increases leaf area index and plant water use, ultimately leading to a decrease in SM due to the combined impacts of CFE in India. This reduction is most prominent in arid regions, where we observe a decline in SM particularly during dry periods. Our study highlights the need to consider plant physiology in land surface modeling under increased CO2 concentration.

Methylosinus trichosporium OB3b drives composition-independent application of biogas in poly(3-hydroxybutyrate) synthesis

Biological conversion of biogas into poly(3-hydroxybutyrate) (PHB) via Type II methanotrophs holds great promise. However, a prerequisite for widespread biogas utilization is a comprehensive understanding of the effects of biogas composition on methanotrophic PHB synthesis. Herein, we explore the effects of biogas composition on the microbial growth and PHB accumulation of Methylosinus trichosporium OB3b under five different artificial biogas conditions with varying the ratio of methane (CH4) to carbon dioxide (CO2), the two main components of raw biogas. Stoichiometric and kinetic analyses revealed that increased CO2 concentrations correlated with higher maximum specific growth rates (0.021–0.029 h−1) and maximum CH4 utilization rates (0.029–0.042 mg CH4/mg TSS-h). Besides, no significant correlation was found between the CH4-to-CO2 ratio and other growth parameters. Consistent PHB contents (20.2–25.3 wt%) were achieved, irrespective of the CH4-to-CO2 ratio. Furthermore, the ability of M. trichosporium OB3b to grow and synthesize PHB (13.2 wt%) was confirmed using pilot-scale biogas. Our findings highlight the potential of biogas as a feedstock for producing valuable biodegradable polymers, thus contributing to waste-derived fuel (WDF) innovation and environmental sustainability.

Century-long timelines of herbarium genomes predict plant stomatal response to climate change

Dissecting plant responses to the environment is key to understanding whether and how plants adapt to anthropogenic climate change. Stomata, plants’ pores for gas exchange, are expected to decrease in density following increased CO2 concentrations, a trend already observed in multiple plant species. However, it is unclear whether such responses are based on genetic changes and evolutionary adaptation. Here we make use of extensive knowledge of 43 genes in the stomatal development pathway and newly generated genome information of 191 Arabidopsis thaliana historical herbarium specimens collected over 193 years to directly link genetic variation with climate change. While we find that the essential transcription factors SPCH, MUTE and FAMA, central to stomatal development, are under strong evolutionary constraints, several regulators of stomatal development show signs of local adaptation in contemporary samples from different geographic regions. We then develop a functional score based on known effects of gene knock-out on stomatal development that recovers a classic pattern of stomatal density decrease over the past centuries, suggesting a genetic component contributing to this change. This approach combining historical genomics with functional experimental knowledge could allow further investigations of how different, even in historical samples unmeasurable, cellular plant phenotypes may have already responded to climate change through adaptive evolution.

Advancing biohydrogen production through indirect photolysis: Insights from numerical simulation using the lattice boltzmann method

Hydrogen production through biochemical reactions is regarded as one of the most potential alternative technologies for producing hydrogen because of its efficacy, renewability, and environmental friendliness. Indirect biophotolysis is one of the most potential biohydrogen production technologies. In this study, a platform based on a coupled lattice Boltzmann method with cellular automata (LBM-CA) was developed to investigate the effects of different illumination intensities and carbon dioxide (CO2) concentrations on indirect photolysis in a bioreactor. The bioreactor was divided into two distinct parts. The first part as a photobioreactor had a transparent window at the top wall of the bioreactor that allowed solar illumination to enter the domain to generate glucose through the conversion of CO2 to carbohydrates (such as glucose) while the second was opaque where hydrogen was produced from carbohydrates by microorganisms. The results show that in the first part of the bioreactor, biofilm grew once CO2 was available. However, there is a lag in the biofilm growthand biohydrogen production between the first and the second part of the bioreactor because they depend on glucose production in the first part. The biofilm concentration increased as illumination increased, especially in the early stages, while the biofilm growth mainly occurred in the first part of the bioreactor. Increasing illumination could increase biofilm concentration by 92.4 % and reduce the lag time. It is also observed that increasing CO2 concentration changed the normalized biofilm concentration considerably, from − 40.9 % to 18.8 %. This can be attributed to increased nutrient availability for microorganism growth and glucose production in the first part of biophotolysis, resulting in greater concentrations of glucose as the main nutrient in the next part. Changing the inlet concentration leads to variations in the normalized hydrogen concentration in the range of − 72.9 % to 49.5 %.

Changes in raspberry sensory quality after harvest as affected by CO2 atmospheres

CO2 atmospheres have the potential to influence raspberry (Rubus idaeus L.) sensory quality after harvest. Our study determined the optimal postharvest atmosphere to extend shelf life without negatively impacting sensory quality. Raspberry fruit were stored at 5 ℃ in 15, 8, 5 or 0.03 kPa CO2 in combination with 6, 13, 16 or 21 kPa O2, respectively. A trained sensory panel conducted a descriptive sensory evaluation of the raspberry fruit after 5, 10, and 13 d of storage. Raspberries stored in 15 kPa CO2 with 6 kPa O2 (15 kPa) atmosphere followed by that in 8 kPa CO2 with 13 kPa O2 (8 kPa) atmosphere had higher firmness than that in 5 kPa CO2 with 16 kPa O2 (5 kPa) and 0.03 kPa CO2 with 21 kPa O2 (0.03 kPa) atmosphere. Panelists found that raspberries stored in 8 kPa and 15 kPa CO2 atmosphere had the least off-flavor and highest tartness. Raspberries stored in 8 kPa scored highest in raspberry flavor with substantial juiciness and sweetness scores. The fermentative volatiles acetaldehyde and ethanol were higher in raspberries stored in 15 kPa despite the low off-flavor scores, while most other raspberry volatiles decreased with increasing CO2 concentration, including flavor-related volatiles α-ionone, α-terpineol, limonene and linalool. After 10 d, the quality of raspberries stored in 0.03 kPa or 5 kPa atmosphere had degraded considerably. While 15 kPa atmosphere prolonged shelf life the longest, 8 kPa atmosphere prolonged shelf life to 10 d while maintaining sensory quality and was the best overall atmosphere.

Preparation and characterization of UiO-66-(OH)2/MWCNTs composites for CO2/N2 adsorption separation

The increasing CO2 concentration in the atmosphere can lead to climate change, and CO2 capture technology is one of the most direct and effective means of reducing carbon emissions. In this study, a new composite was prepared in situ by loading multi-walled carbon nanotubes (MWCNTs) onto metal–organic frameworks (MOFs) to efficiently capture CO2 in flue gas. The morphological states and pore structures of the composites were analyzed using characterization methods. The CO2 adsorption properties of the composites were tested at 273 K and 298 K with different MWCNTs loadings. The optimal CO2 adsorption quantities of the composite material were measured to be 4.4 and 5.75 mmol/g, respectively, which increased the adsorption capacity by 66.7 % and 55 %, respectively, compared with the parent material at a pressure of 1 bar. The CO2/N2 separation performance of the composites was examined using ideal adsorption solution theory calculations and dynamic adsorption breakthrough experiments. The stability of the composites was investigated by thermogravimetric analysis, acidification experiments, and cyclical adsorption–desorption experimentation. The UiO-66-(OH)2/MWCNTs composites exhibited superior CO2 adsorption–separation performance, thermal stability, acid resistance, and cycling stability. Therefore, the composite has potential applications in CO2 capture separation technology.

Optimization of metal transfer in rutile flux-cored arc welding through controlled CO2 concentration in argon–CO2 shielding gas

In this study, we analyzed the impact of carbon dioxide concentration in argon–carbon dioxide shielding gas on droplet transfer characteristics in rutile flux-cored arc welding, employing titanium oxide as a primary wire flux component. The welding process was carried out at a welding current of 190, 220, 250, 280, and 310 A under an argon–CO2 shielding gas mixture with six levels of CO2 concentration of 0, 5 %, 10 %, 15 %, 20 %, and 25 % for a parametric study. Unlike the conventional solid wire welding trend, where the droplet transfer frequency decreases with the increase in carbon dioxide concentration, an increase in metal transfer frequency was observed with the increase in CO2 concentration from approximately 5 % to 20 %. The concentration reaching the maximum frequency was 20 % at 190 A, which decreased as the welding current increased, reaching 5 % at 310 A. Droplet initiation at the lower sheath end is succeeded by a gradual downward movement along the flux column's side after a few milliseconds. Upon reaching the lower end, the droplet forms a neck and undergoes separation. Thus, the length of the flux column directly impacts the duration of one droplet transfer cycle. The length was decreased by arc constriction when increasing CO2 concentration appropriately to concentrate beneath the flux column or by increasing the welding current to raise the arc temperature, which contributed to melting and shortening the flux column.

How Does Plant CO2 Physiological Forcing Amplify Amazon Warming in CMIP6 Earth System Models?

AbstractThe physiological response to increasing CO2 concentrations will lead to land surface warming through a redistribution of the energy balance. As the Amazon is one of the most plant‐rich regions, the increase in surface temperature, caused by plant CO2 physiological forcing, is particularly large compared to other regions. In this study, we analyze the outputs of the 11 models in the Coupled Model Intercomparison Project Phase 6 to find out how CO2 physiological forcing amplifies Amazonian warming under elevated CO2 levels. With the CO2 concentration increase from 285 to 823 ppm, the Amazon temperature increased by 0.48 ± 0.42 K as a result of plant physiological forcing. Moreover, we assess the contributions of each climate feedback to the surface warming due to physiological forcing by quantifying climate feedbacks based on radiative kernels. Lapse rate feedback and cloud feedback, analyzed as the primary contributors, accounted for 53% and 37% of Amazon warming, respectively. The warming contributions of these two feedbacks also exhibit a significant spread, which contributes to the predictive uncertainty. The surface warming due to reduced evapotranspiration is larger than the upper tropospheric warming in the Amazon, resulting in surface warming by lapse rate feedback. In addition, cloud cover in the Amazon region decreases due to the reduced evapotranspiration. Decreased cloud cover amplifies surface warming through the shortwave cloud feedback. Furthermore, differences in circulation and local convection caused by physiological effect contribute to the inter‐model spread of the cloud feedback.

Polymer-integrated acoustic graphene plasmon resonator for sensitive detection of CO2 gas

Acoustic graphene plasmons (GPs) exhibit an exceptional density of electromagnetic states within the mid-infrared (MIR) and terahertz frequency ranges, leading to a pronounced near-field amplification and localization at the nanometer scale. This characteristic renders them highly promising for the development of ultra-sensitive plasmon-enhanced MIR sensing and spectroscopic applications. However, the tight spatial confinement inherent to acoustic GPs results in a significant momentum mismatch, which in turn leads to poor coupling efficiency with light in free space. To overcome this limitation, we leverage numerical simulations to show that GPs can act as an intermediary to facilitate efficient excitation of acoustic GPs by incident MIR radiation, achieving an extinction spectrum peak value of approximately 0.9. The proposed gas sensor based on the acoustic GP resonator is composed of pristine, large-area graphene, an array of periodic metal nanocubes, and a slender polyethylenimine (PEI) layer that adsorbs CO2, situated between the nanocubes and the graphene sheet. The sensing performance of the proposed sensor is numerically investigated. It is demonstrated that by incorporating a CO2-absorbing material into the acoustic GPs, we can perform highly sensitive assessments of the absorption bands within the PEI layer upon CO2 adsorption. The observed behavior of the acoustic GPs indicates a weakening and broadening with increasing CO2 concentrations, a phenomenon attributed to the alteration in the permittivity of the PEI in the interstitial layer due to CO2 adsorption. Numerical simulation results indicate that the sensitivity of the proposed hybrid gas sensor can reach up to 0.0183% ppm−1, which offers a remarkable 95-fold enhancement over the gas sensor based on graphene nanoribbons. Our findings underscore the potential of acoustic GP nanoresonators as a transformative platform for ultrasensitive plasmon-enhanced sensing applications, particularly when integrated with various gas adsorption layers or molecular agents.

Elevated CO2 concentration enhance carbon and nitrogen metabolism and biomass accumulation of Ormosiahosiei

Elevated CO2 concentrations may inhibit photosynthesis due to nitrogen deficiency, but legumes may be able to overcome this limitation and continue to grow. Our study confirms this conjecture well. First, we placed the two-year-old potted saplings of Ormosia hosiei (O. hosiei) (a leguminous tree species) in the open-top chamber (OTC) with three CO2 concentrations of 400 (CK), 600 (E1), and 800 μmol·mol−1 (E2) to simulate the elevated CO2 concentration environment. After 146 days, the light saturation point (LSP), light compensation point (LCP), apparent quantum efficiency (AQE), and dark respiration rate (Rd) of O. hosiei were increased under increasing CO2 concentration and obtain the maximum ribulose diphosphate (RuBP) carboxylation rate (Vc max) and RuBP regenerated photosynthetic electron transfer rate (Jmax) were also significantly increased under E2 treatment (P < 0.05). This results in a significant increase of the maximum assimilation rate (Amax) under elevated CO2 concentrations. Sucrose phosphate synthase (SPS) activity in sucrose metabolism increased in the leaves, more soluble sugars, starches, and sucrose was produced, but sucrose content only in leaves increased at E2, and more carbon flows to the roots. The activity of the NH4+ assimilating enzymes glutamine synthetase (GS), glutamate synthetase (GOGAT), and glutamate dehydrogenase (GDH) in the leaves of O. hosiei increases under elevated CO2 concentrations to promote nitrogen synthesis that reduces the content of ammonium nitrogen and increases the content of nitrate nitrogen. In addition, under E1 conditions, sucrose synthase (SS), direction of synthesis activity was highest and sucrose invertase (INV) activity was lowest, this means that the balance of C and N metabolism is maintained. While under E2 conditions SS activity decreased and INV activity increased, this increased C/N and nitrogen use efficiency. So, the elevated CO2 concentration promotes the accumulation of O. hosiei biomass, especially in the aboveground part, but did not have a significant effect on the accumulation of root biomass. This means that O. hosiei is able to cope under the elevated CO2 concentration without showing photosynthetic adaptation during the experimental period.

The Role of Diabatic Heating in the Midlatitude Atmospheric Circulation Response to Climate Change

Abstract Climate models generally predict a poleward shift of the midlatitude circulation in response to climate change induced by increased greenhouse gas concentration, but the intermodel spread of the eddy-driven jet shift is large and poorly understood. Recent studies point to the significance of midlatitude midtropospheric diabatic heating for the intermodel spread in the jet latitude. To examine the role of diabatic heating in the jet response to climate change, a series of simulations are performed using an idealized aquaplanet model. It is found that both increased CO2 concentration and increased saturation vapor pressure induce a similar warming response, leading to a poleward and upward shift of the midlatitude circulation. An exception to this poleward shift is found for a certain range of temperatures, where the eddy-driven jet shifts equatorward, while the latitude of the eddy heat flux remains essentially unchanged. This equatorward jet shift is explained by the connection between the zonal-mean momentum and heat budgets: increased diabatic heating in the midlatitude midtroposphere balances the cooling by the Ferrel cell ascending branch, enabling an equatorward shift of the Ferrel cell streamfunction and eddy-driven jet, while the latitude of the eddy heat flux remains unchanged. The equatorward jet shift and the strengthening of the midlatitude diabatic heating are found to be sensitive to the model resolution. The implications of these results for a potential reduction in the jet shift uncertainty through the improvement of convective parameterizations are discussed. Significance Statement The latitude of the eddy-driven jet displays considerable variation in climate models, and the factors influencing this variability are poorly understood. This work connects the strength of midlatitude diabatic heating to the structure of the midlatitude circulation and the eddy-driven jet latitude. The direction of the eddy-driven jet shift in response to climate change is found to depend on the diabatic heating response, which in turn depends on the parameterized convective heating. These results highlight the role of convective parameterizations in the representation of the midlatitude circulation in climate models. Additionally, the results imply that the eddy-driven jet shift cannot be explained solely based on the storm-track response to climate change, in contrast with previously suggested explanations.

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.

Rain use efficiency gradients across Australian ecosystems

Rain use efficiency (RUE) quantifies the ecosystem's capacity to use precipitation water to assimilate atmospheric CO2. The spatial distribution of RUE and its drivers across the Australian continent is largely unknown. This knowledge gap limits our understanding of the possible contribution of Australian ecosystems to global carbon assimilation. This study investigates the spatial distribution of RUE across diverse terrestrial ecosystems in Australia. The results show that RUE ranges from 0.43 (1st percentile) to 3.10 (99th percentile) g C m−2 mm−1 with a continental mean of 1.19 g C m−2 mm−1. About 68 % of the spatiotemporal variability of RUE can be explained by a multiple linear regression model primarily contributed by climatic predictors. Benchmarked by the model estimation, drainage-diverging/converging landscapes tend to have reduced/increased RUE. The model also revealed the impact of increasing atmospheric CO2 concentration on RUE. The continental mean RUE would increase by between 29.3 and 64.8 % by the end of this century under the SSP5–8.5 scenario in which the CO2 concentration is projected to double from the present level. This increase in projected RUE is attributed to the assumed greening effect of increasing CO2 concentration, which does not consider the saturation of CO2 fertilisation effect and the warming effect on increasing wildfire occurrence. Under the SSP1–2.6 scenario, RUE would decrease by about 7 %. This study provides baseline RUEs of various ecosystems in Australia for investigating the impacts of human interferences and climate change on the capacity of Australian vegetation to assimilate atmospheric CO2 under given precipitation.

CO2 response screen in grass Brachypodium reveals the key role of a MAP kinase in CO2-triggered stomatal closure.

Plants respond to increased CO2 concentrations through stomatal closure, which can contribute to increased water use efficiency. Grasses display faster stomatal responses than eudicots due to dumbbell-shaped guard cells flanked by subsidiary cells working in opposition. However, forward genetic screening for stomatal CO2 signal transduction mutants in grasses has yet to be reported. The grass model Brachypodium distachyon is closely related to agronomically important cereal crops, sharing largely collinear genomes. To gain insights into CO2 control mechanisms of stomatal movements in grasses, we developed an unbiased forward genetic screen with an EMS-mutagenized B. distachyon M5 generation population using infrared imaging to identify plants with altered leaf temperatures at elevated CO2. Among isolated mutants, a "chill1" mutant exhibited cooler leaf temperatures than wild-type Bd21-3 parent control plants after exposure to increased CO2. chill1 plants showed strongly impaired high CO2-induced stomatal closure despite retaining a robust abscisic acid-induced stomatal closing response. Through bulked segregant whole-genome sequencing analyses followed by analyses of further backcrossed F4 generation plants and generation and characterization of sodium azide and CRISPR-cas9 mutants, chill1 was mapped to a protein kinase, Mitogen-Activated Protein Kinase 5 (BdMPK5). The chill1 mutation impaired BdMPK5 protein-mediated CO2/HCO3- sensing together with the High Temperature 1 (HT1) Raf-like kinase in vitro. Furthermore, AlphaFold2-directed structural modeling predicted that the identified BdMPK5-D90N chill1 mutant residue is located at the interface of BdMPK5 with the BdHT1 Raf-like kinase. BdMPK5 is a key signaling component that mediates CO2-induced stomatal movements and is proposed to function as a component of the primary CO2 sensor in grasses.

Entropy Drives Accelerated Ion Diffusion upon Carbon Dioxide Expansion of Electrolytes.

Carbon dioxide-expanded liquids, organic solvents with high concentrations of soluble carbon dioxide (CO2) at mild pressures, have gained attention as green catalytic media due to their improved properties over traditional solvents. More recently, carbon dioxide-expanded electrolytes (CXEs) have demonstrated improved reaction rates in the electrochemical reduction of CO2, by increasing the rate of delivery of CO2 to the electrode while maintaining facile charge transport. However, recent studies indicate that the limiting behavior of CXEs at higher CO2 pressures is a decline in solution conductivity due to reduced polarity, leading to poorer charge screening and greater ion pairing. In this article, we employ molecular dynamics simulations to investigate the energetic driving forces behind the diffusive properties of an acetonitrile and tetrapropylammonium hexafluorophosphate (TPrAPF6) CXE with increasing CO2 concentration. Our results indicate that entropy drives solvent and electrolyte diffusion with increasing CO2 pressure. The activation energy of ion diffusion increases with higher concentrations of CO2, indicating that increasing the temperature may improve solution conductivity in these systems. This trend in the activation energies is traced to stronger cation-anion Coulombic interactions due to weaker solvent screening at high CO2 concentrations, suggesting that the choice of ion may provide a route to diminish this effect.

Perspectives on improving photosynthesis to increase crop yield.

Improving photosynthesis, the fundamental process by which plants convert light energy into chemical energy, is a key area of research with great potential for enhancing sustainable agricultural productivity and addressing global food security challenges. This perspective delves into the latest advancements and approaches aimed at optimizing photosynthetic efficiency. Our discussion encompasses the entire process, beginning with light harvesting and its regulation and progressing through the bottleneck of electron transfer. We then delve into the carbon reactions of photosynthesis, focusing on strategies targeting the enzymes of the Calvin-Benson-Bassham (CBB) cycle. Additionally, we explore methods to increase carbon dioxide (CO2) concentration near the Rubisco, the enzyme responsible for the first step of CBB cycle, drawing inspiration from various photosynthetic organisms, and conclude this section by examining ways to enhance CO2 delivery into leaves. Moving beyond individual processes, we discuss two approaches to identifying key targets for photosynthesis improvement: systems modeling and the study of natural variation. Finally, we revisit some of the strategies mentioned above to provide a holistic view of the improvements, analyzing their impact on nitrogen use efficiency and on canopy photosynthesis.