Presence Of Elevated CO2 Research Articles

Elevated CO2 ameliorates the high temperature stress effects on physio-biochemical, growth, yield traits of maize hybrids

The rising temperatures and levels of carbon dioxide in the atmosphere are anticipated to have a significant impact on the productivity of agricultural crops. Although, the individual effects of elevated CO2 and temperature have been extensively studied in C3 and C4 crops, there remains a scarcity of research investigating their interactive effects specifically on maize hybrids. The impact of elevated temperature and its interaction with elevated CO2 on phenology, physiology, biomass, and grain yield of maize hybrids was assessed in a field experiment using Free Air Temperature Elevation (FATE) facility. The results showed that elevated temperature (eT) increased the anthesis silking interval (ASI), while the presence of elevated CO2 along with elevated temperature (eT + eCO2) mitigated this effect. The differential expression were observed between hybrids depending on their genetic potential. Furthermore, the net photosynthetic rate (Anet), stomatal conductance (gs), and transpiration rate (Tr) of hybrids decreased under elevated temperature but eT + eCO2 condition helped in reverting its impact to some extent. In term of leaf composition, the highest level of total soluble sugars (TSS) and starch was observed under eT + eCO2 conditions, possibly due to improved Anet in the presence of elevated eCO2. The negative impact of eT was also evident through increased proline and MDA content, but eT + eCO2 ameliorated the adverse effect of eT. The biomass and grain yield also responded similarly, among the hybrids 900M GOLD recorded superior performance for grain yield at eT condition exceeding 35 °C. On the other hand, DHM117 experienced a significant reduction in grain yield under eT, but performed better under eT + eCO2 due to its improved physiological response to eCO2. The study indicated that elevated levels of carbon dioxide can actually mitigate the detrimental effects of elevated temperature on maize crop. This positive impact on maize crop can be attributed to an enhanced physiological performance in the presence of eCO2 which enables the plants to maintain satisfactory yield levels despite the challenging environmental conditions.

Lemnaceae as Novel Crop Candidates for CO2 Sequestration and Additional Applications.

Atmospheric carbon dioxide (CO2) is projected to be twice as high as the pre-industrial level by 2050. This review briefly highlights key responses of terrestrial plants to elevated CO2 and compares these with the responses of aquatic floating plants of the family Lemnaceae (duckweeds). Duckweeds are efficient at removing CO2 from the atmosphere, which we discuss in the context of their exceptionally high growth rates and capacity for starch storage in green tissue. In contrast to cultivation of terrestrial crops, duckweeds do not contribute to CO2 release from soils. We briefly review how this potential for contributions to stabilizing atmospheric CO2 levels is paired with multiple additional applications and services of duckweeds. These additional roles include wastewater phytoremediation, feedstock for biofuel production, and superior nutritional quality (for humans and livestock), while requiring minimal space and input of light and fertilizer. We, furthermore, elaborate on other environmental factors, such as nutrient availability, light supply, and the presence of a microbiome, that impact the response of duckweed to elevated CO2. Under a combination of elevated CO2 with low nutrient availability and moderate light supply, duckweeds' microbiome helps maintain CO2 sequestration and relative growth rate. When incident light intensity increases (in the presence of elevated CO2), the microbiome minimizes negative feedback on photosynthesis from increased sugar accumulation. In addition, duckweed shows a clear propensity for absorption of ammonium over nitrate, accepting ammonium from their endogenous N2-fixing Rhizobium symbionts, and production of large amounts of vegetative storage protein. Finally, cultivation of duckweed could be further optimized using hydroponic vertical farms where nutrients and water are recirculated, saving both resources, space, and energy to produce high-value products.

Effects of combined abiotic stresses on nutrient content of European wheat and implications for nutritional security under climate change

Climate change is causing problems for agriculture, but the effect of combined abiotic stresses on crop nutritional quality is not clear. Here we studied the effect of 10 combinations of climatic conditions (temperature, CO2, O3 and drought) under controlled growth chamber conditions on the grain yield, protein, and mineral content of 3 wheat varieties. Results show that wheat plants under O3 exposure alone concentrated + 15 to + 31% more grain N, Fe, Mg, Mn P and Zn, reduced K by − 5%, and C did not change. Ozone in the presence of elevated CO2 and higher temperature enhanced the content of Fe, Mn, P and Zn by 2–18%. Water-limited chronic O3 exposure resulted in + 9 to + 46% higher concentrations of all the minerals, except K. The effect of climate abiotic factors could increase the ability of wheat to meet adult daily dietary requirements by + 6% to + 12% for protein, Zn and Fe, but decrease those of Mg, Mn and P by − 3% to − 6%, and K by − 62%. The role of wheat in future nutrition security is discussed.

Effects of Combined CO2 and O3 Exposures on Net CO2 Assimilation and Biomass Allocation in Seedlings of the Late-Successional Fagus Crenata

We examined the effects of elevated CO2 and elevated O3 concentrations on net CO2 assimilation and growth of Fagus crenata in a screen-aided free-air concentration-enrichment (FACE) system. Seedlings were exposed to ambient air (control), elevated CO2 (550 µmol mol−1 CO2, +CO2), elevated O3 (double the control, +O3), and the combination of elevated CO2 and O3 (+CO2+O3) for two growing seasons. The responses in light-saturated net CO2 assimilation rates per leaf area (Agrowth-CO2) at each ambient CO2 concentration to the elevated CO2 and/or O3 treatments varied widely with leaf age. In older leaves, Agrowth-CO2 was lower in the presence of +O3 than in untreated controls, but +CO2+O3 treatment had no effect on Agrowth-CO2 compared with the +CO2 treatment. Total plant biomass increased under conditions of elevated CO2 and was largest in the +CO2+O3 treatment. Biomass allocation to roots decreased with elevated CO2 and with elevated O3. Elongation of second-flush shoots also increased in the presence of elevated CO2 and was largest in the +CO2+O3 treatment. Collectively, these results suggest that conditions of elevated CO2 and O3 contribute to enhanced plant growth; reflecting changes in biomass allocation and mitigation of the negative impacts of O3 on net CO2 assimilation.

Roles of heat shock protein and reprogramming of photosynthetic carbon metabolism in thermotolerance under elevated CO2 in maize

Our previous published results demonstrated that elevated CO2 can reprogram photosynthetic carbon metabolism (PCM) during sudden heat stress (SHS) treatments. However, the mechanism explaining how elevated CO2 could regulate the metabolites through SHS-induced proteins is poorly understood. Here, we combined metabolism and transcriptomes analysis to elucidate the differential genes expression of key heat shock proteins (HSPs) under SHS in presence of elevated CO2. Our results show strong positive correlation in terms of carbon assimilation rates (A) between both field open top chamber (OTCs) and growth chamber conditions. The decline in A during SHS is ascribable to a metabolic reprogramming rather than stomatal-limitation. We recorded an increase by about 3 ˜ 4 times in the expression levels of small HSPs, especially Cpn2 and Hsp1 following elevated CO2. This study underlines the beneficial effects of elevated CO2 in the thermotolerance process through amplifying small HSPs in maize. Our current investigation suggests a potential mechanistic model for the metabolic network reprogramming following combined effect of SHS and elevated CO2. It corroborates as well the involvement of two HSPs genes in the in the adjustment of photosynthetic carbon metabolism pathway to avoid any misfolding in Rubisco subunits proteins.

Responses of Bougainvillea spectabilis to elevated atmospheric CO2 under galaxolide (HHCB) pollution and the mechanisms of its rhizosphere metabolism

Due to the discovery of synthetic musks in soil and the gradual increase in atmospheric carbon dioxide (CO2), it is important to reveal the potential implications of these compounds for bioremediation systems. Hence, this study was conducted to investigate the combined influence of galaxolide (HHCB) and elevated CO2 on an ornamental remediation plant. We conducted pot experiments with Bougainvillea spectabilis, an ornamental remediation plant, in which the biomass, HHCB and chlorophyll contents, and rhizosphere metabolism of the plants were analyzed. We showed that B. spectabilis exhibited high tolerance under combined HHCB and elevated CO2 stresses. The addition of HHCB alone to the soil did not significantly reduce the biomass components of B. spectabilis, whereas the presence of elevated CO2 (750 μL L−1) alone showed a relatively strong ability to increase plant biomass, especially that of the leaves. An elevated CO2 concentration stimulated the absorption of low doses of HHCB by the roots. Regarding the root metabolites of B. spectabilis, carbohydrates and organic acids were highly correlated with HHCB concentration, and amino acids were well correlated with CO2 concentration. Our study indicates that B. spectabilis may be well suited to remove HHCB from contaminated soil under elevated CO2 levels, and the root metabolism of this plant provides information about HHCB contamination and elevated CO2 conditions.

Effect of low-level CO2 on innate inflammatory protein response to organic dust from swine confinement barns

BackgroundOrganic hog barn dust (HDE) exposure induces lung inflammation and long-term decreases in lung function in agricultural workers. While concentrations of common gasses in confined animal facilities are well characterized, few studies have been done addressing if exposure to elevated barn gasses impacts the lung immune response to organic dusts. Given the well documented effects of hypercapnia at much higher levels we hypothesized that CO2 at 8 h exposure limit levels (5000 ppm) could alter innate immune responses to HDE.MethodsUsing a mouse model, C57BL/6 mice were nasally instilled with defined barn dust extracts and then housed in an exposure box maintained at one of several CO2 levels for six hours. Bronchiolar lavage (BAL) was tested for several cytokines while lung tissue was saved for mRNA purification and immunohistochemistry.ResultsExposure to elevated CO2 significantly increased the expression of pro-inflammatory markers, IL-6 and KC, in BAL fluid as compared to dust exposure alone. Expression of other pro-inflammatory markers, such as ICAM-1 and matrix metalloproteinase-9 (MMP-9), were also tested and showed similar increased expression upon HDE + CO2 exposure. A chemokine array analysis of BAL fluid revealed that MIP-1γ (CCL9) shows a similar increased response to HDE + CO2. Further testing showed CCL9 was significantly elevated by barn dust and further enhanced by CO2 co-exposure in a dose-dependent manner that was noticeable at the protein and mRNA levels. In all cases, except for ICAM-1, increases in tested markers in the presence of elevated CO2 were only significant in the presence of HDE as well.ConclusionsWe show that even at mandated safe exposure limits, CO2 is capable of enhancing multiple markers of inflammation in response to HDE.

Zebrafish (Danio rerio) behaviour is largely unaffected by elevated pCO2.

Ocean acidification, the decrease in ocean pH caused by anthropogenic emission of carbon dioxide, can cause behavioural disturbances in marine teleost species. We investigated whether AB-strain zebrafish (Danio rerio) show similar behavioural disturbances in the presence of elevated CO2, because this model species could open up a toolbox to investigate the physiological and neurological mechanisms of CO2 exposure. We found no effect of elevated CO2 (~1600 μatm) on the behaviour of zebrafish in the open field test, indicating that zebrafish are largely insensitive to this elevated CO2 level. In the detour test of lateralization, however, zebrafish exposed to elevated CO2 swam more often to the right, whereas individuals exposed to control CO2 (~400 μatm) had no preference for left or right. This may indicate that some behaviours of some freshwater fishes can be altered by elevated CO2 levels. Given that elevated CO2 levels often occur in recirculating aquaculture and aquarium systems, we recommend that dissolved CO2 levels are measured and, if necessary, the aquarium water should be aerated, in order to exclude CO2 level as a confounding factor in experiments.

Warming and elevated CO2 combine to increase microbial mineralisation of soil organic matter

The net annual exchange of carbon between the atmosphere and terrestrial ecosystems is of prime importance in determining the concentration of CO2 ([CO2]) in the atmosphere and consequently future climate. Carbon loss occurs primarily through soil respiration; it is known that respiration is sensitive to the global changes in [CO2] and temperature, suggesting that the net carbon balance may change in the future. However, field manipulations of temperature and [CO2] alter many important environmental factors so it is unclear how much of the observed alterations in soil respiration is due to changes of microbial function itself instead of changes to the physical and chemical environment. Here we focus on resolving the importance of changes in the microbial community in response to warming and elevated [CO2] on carbon mineralisation, something not possible in field measurements. We took plant material and soil inocula from a long running experiment where native grassland had been exposed to both warming and elevated CO2 and constructed a reciprocal transplant experiment. We found that the rate of decomposition (heterotrophic respiration) was strongly determined by the origin of the microbial community. The combined warming + elevated CO2 treatment produced a soil community that gave respiration rates 30% higher when provided with shoot litter and 70% for root litter than elevated CO2 treatment alone, with the treatment source of the litter being unimportant. Warming, especially in the presence of elevated CO2, increased the size of the apparent labile carbon pool when either C3 or C4 litter was added. Thus, the metabolic activity of the soil community was affected by the combination of warming and elevated CO2 such that it had an increased ability to mineralise added organic matter, regardless of its source. Therefore, soil C efflux may be substantially increased in a warmer, high CO2 world. Current ecosystem models mostly drive heterotrophic respiration from plant litter quality, soil moisture and temperature but our findings suggest equal attention will need to be paid to capturing microbial processes if we are to accurately project the future C balance of terrestrial ecosystems and quantify the feedback effect on atmospheric concentrations of CO2.

CO2 leakage impacts on shallow groundwater: Field-scale reactive-transport simulations informed by observations at a natural analog site

It is challenging to predict the degree to which shallow groundwater might be affected by leaks from a CO2 sequestration reservoir, particularly over long time scales and large spatial scales. In this study observations at a CO2 enriched shallow aquifer natural analog were used to develop a predictive model which is then used to simulate leakage scenarios. This natural analog provides the opportunity to make direct field observations of groundwater chemistry in the presence of elevated CO2, to collect aquifer samples and expose them to CO2 under controlled conditions in the laboratory, and to test the ability of multi-phase reactive transport models to reproduce measured geochemical trends at the field-scale. The field observations suggest that brackish water entrained with the upwelling CO2 are a more significant source of trace metals than in situ mobilization of metals due to exposure to CO2. The study focuses on a single trace metal of concern at this site: U. Experimental results indicate that cation exchange/adsorption and dissolution/precipitation of calcite containing trace amounts of U are important reactions controlling U in groundwater at this site, and that the amount of U associated with calcite is fairly well constrained. Simulations incorporating these results into a 3-D multi-phase reactive transport model are able to reproduce the measured ranges and trends between pH, pCO2, Ca, total C, U and Cl− at the field site. Although the true fluxes at the natural analog site are unknown, the cumulative CO2 flux inferred from these simulations are approximately equivalent to 37.8E−3MT, approximately corresponding to a .001% leak rate for injection at a large (750MW) power plant. The leakage scenario simulations suggest that if the leak only persists for a short time the volume of aquifer contaminated by CO2-induced mobilization of U will be relatively small, yet persistent over 100 a.

Sch9 Kinase Integrates Hypoxia and CO 2 Sensing To Suppress Hyphal Morphogenesis in Candida albicans

The yeast-hypha transition is an important virulence trait of Candida albicans. We report that the AGC kinase Sch9 prevents hypha formation specifically under hypoxia at high CO(2) levels. sch9 mutants showed no major defects in growth and stress resistance but a striking hyperfilamentous phenotype under hypoxia (<10% O(2)), although only in the presence of elevated CO(2) levels (>1%) and at temperatures of <37°C during surface growth. The sch9 hyperfilamentous phenotype was independent of Rim15 kinase and was recreated by inhibition of Tor1 kinase by rapamycin or caffeine in a wild-type strain, suggesting that Sch9 suppression requires Tor1. Caffeine inhibition also revealed that both protein kinase A isoforms, as well as transcription factors Czf1 and Ace2, are required to generate the sch9 mutant phenotype. Transcriptomal analyses showed that Sch9 regulates most genes solely under hypoxia and in the presence of elevated CO(2). In this environment, Sch9 downregulates genes encoding cell wall proteins and nutrient transporters, while under normoxia Sch9 and Tor1 coregulate a minor fraction of Sch9-regulated genes, e.g., by inducing glycolytic genes. Other than in Saccharomyces cerevisiae, both sch9 and rim15 mutants showed decreased chronological aging under normoxia but not under hypoxia, indicating significant rewiring of the Tor1-Sch9-Rim15 pathway in C. albicans. The results stress the importance of environmental conditions on Sch9 function and establish a novel response circuitry to both hypoxia and CO(2) in C. albicans, which suppresses hypha formation but also allows efficient nutrient uptake, metabolism, and virulence.

Growth and Resource Use of Birch Seedlings Under Elevated Carbon Dioxide and Temperature

The effects of elevated CO2and temperature on the growth, resource acquisition and resource allocation of small birch seedlings (Betula pendula Roth.) were examined under conditions of non-limiting soil, water and nutrient supply. Seedlings were planted in pots and placed in controlled environment chambers either under normal ambient conditions (CON), or in the presence of elevated CO2(approx. 700μmolmol−1; Elev. C), elevated temperature (approx. 3°C above the outside ambient temperature; Elev. T) or a combination of elevated CO2and elevated temperature (Elev. C+T). Both Elev. C and Elev. T significantly increased biomass accumulation, but the extent of the increase depended greatly on the stage of development of the seedlings. Furthermore, the theoretically expected positive effect of the warmer temperature on the CO2-induced stimulation of growth was not observed. By analysing resource acquisition (i.e. CO2, nitrogen and water uptake), seedling development, leaf area production and the allocation pattern, it was deduced that the CO2-stimulated increase in biomass resulted mainly from the initial ‘fertilization’ effect of CO2while the temperature-induced increase in biomass stemmed from higher net carbon intake during the middle and latter parts of the growing season achieved by virtue of the increased leaf area and larger photosynthetic capacity. The lack of positive stimulation by temperature under Elev. C+T may be related in part to (1) CO2-induced acceleration of seedling development, which led to a small or no response to CO2enrichment and lower leaf area production during the latter part of the growth season, and (2) a cumulative delay in the response of growth to the warmer temperature, which did not increase net carbon intake when the seedlings were at a juvenile stage. Neither Elev. C nor Elev. T altered the root:shoot ratio during early growth, but Elev. C increased it during the latter part of the growth season while Elev. T decreased it, possibly on account of a change in leaf area retention. Finally, the nitrogen and water use efficiencies of seedlings at different stages of development are discussed.

Effects of elevated CO2 and O3 on the rate and duration of grain growth and harvest index in spring wheat (Triticum aestivum L.)

AbstractWheat (Triticum aestivum L.) cv. Minaret was grown in open‐top chambers (OTCs) in 1995 and 1996 under three carbon dioxide (CO2) and two ozone (O3) levels. Plants were harvested regularly between anthesis and maturity to examine the rate of grain growth (dG/dt; mg d–1) and the rate of increase in harvest index (dHI/dt;% d–1). The duration of grain filling was not affected by elevated CO2 or O3, but was 12 days shorter in 1995, when the daily mean temperature was over 3 °C higher than in 1996. Season‐long exposure to elevated CO2 (680 μmol mol–1) significantly increased the rate of grain growth in both years and mean grain weight at maturity (MGW) was up to 11% higher than in the chambered ambient air control (chAA; 383 μmol mol–1). However, the increase in final yield obtained under elevated CO2 relative to the chAA control in 1996 resulted primarily from a 27% increase in grain number per unit ground area. dG/dt was significantly reduced by elevated O3 under ambient CO2 conditions in 1995, but final grain yield was not affected because of a concurrent increase in grain number. Neither dG/dt nor dHI/dt were affected by the higher mean O3 concentrations applied in 1996 (77 vs. 66 nmol mol–1); the differing effects of O3 on grain growth in 1995 and 1996 observed in both the ambient and elevated CO2 treatments may reflect the contrasting temperature environments experienced. Grain yield was nevetheless reduced under elevated O3 in 1996, primarily because of a substantial decrease in grain number. The data obtained show that, although exposure to elevated CO2 and O3 individually or in combination may affect both dG/dt and dHI/dt, the presence of elevated CO2 does not protect against substantial O3‐induced yield losses resulting from its direct deleterious impact on reproductive processes. The implications of these results for food production under future climatic conditions are considered.

Response of tussock tundra to elevated carbon dioxide regimes: analysis of ecosystem CO2 flux through nonlinear modeling.

The response of tussock tundra to elevated atmospheric concentrations of CO2 was measured at Toolik Lake, Alaska in the summer of 1983. Computer-controlled greenhouses were used to determine diurnal ecosystem flux of CO2 under four treatments: 340 ppm, 510 ppm, and 680 ppm CO2, as well as 680 ppm CO2 with a four degree centrigrade increase in temperature. For the seven days of data analyzed, net daily CO2 flux was significantly different between treatments. Net uptake was positively correlated with CO2 concentration in the chamber and negatively correlated with temperature. A nonlinear model was used to analyze this data set and to determine some of the reasons for different net CO2 flux. This model allowed an estimation of light utilization efficiency, total conductance of CO2, and a comparable measure of total respiration. From this analysis we conclude that nutrient limitations in the arctic decrease the capacity of tundra plants to make use of elevated CO2 concentrations. The plants respond by decreasing conductance in the presence of elevated CO2, which results in approximately equal gross uptake rates for the three CO2 treatments. Apparent changes in system respiration result in higher net uptake under elevated CO2 but this may be due to biases in the data. The treatment with increased temperature exhibited higher conductances and, consequently, higher gross uptake of CO2 than the other treatments. Higher temperatures, however, also increase respiration with the result being lower net uptake than would be expected in the absence of temperature inscreases.