Ambient CO2 Levels Research Articles

Efficient utilization of xylose requires CO2 fixation in Synechococcus elongatus PCC 7942

Cyanobacteria show great promise as autotrophic hosts for the renewable biosynthesis of useful chemicals from CO2 and light. While they can efficiently fix CO2, cyanobacteria are generally outperformed by heterotrophic production hosts in terms of productivity and titer. Photomixotrophy, or co-utilization of sugars and CO2 as carbon feedstocks, has been implemented in cyanobacteria to greatly improve productivity and titers of several chemical products. We introduced xylose photomixotrophy to a 2,3-butanediol producing strain of Synechococcus elongatus PCC 7942 and characterized the effect of gene knockouts, changing pathway expression levels, and changing growth conditions on chemical production. Interestingly, 2,3-butanediol production was almost completely inhibited in the absence of added CO2. Untargeted metabolomics implied that RuBisCO was a significant bottleneck, especially at ambient CO2 levels, restricting the supply of lower glycolysis metabolites needed for 2,3-butanediol production. The dependence of the strain on elevated CO2 levels suggests some practical limitations on how xylose photomixotrophy can be efficiently carried out in S. elongatus.

Morphophysiological, biochemical, and nutrient response of spinach (Spinacia oleracea L.) by foliar CeO2 nanoparticles under elevated CO2

Nanomaterials offer considerable benefits in improving plant growth and nutritional status owing to their inherent stability, and efficiency in essential nutrient absorption and delivery. Cerium oxide nanoparticles (CeO2 NPs) at optimum concentration could significantly influence plant morpho-physiology and nutritional status. However, it remains unclear how elevated CO2 and CeO2 NPs interactively affect plant growth and quality. Accordingly, the ultimate goal was to reveal whether CeO2 NPs could alter the impact of elevated CO2 on the nutrient composition of spinach. For this purpose, spinach plant morpho-physiological, biochemical traits, and nutritional contents were evaluated. Spinach was exposed to different foliar concentrations of CeO2 NPs (0, 25, 50, 100 mg/L) in open-top chambers (400 and 600 CO2 μmol/mol). Results showed that elevated CO2 enhanced spinach growth by increasing photosynthetic pigments, as evidenced by a higher photosynthetic rate (Pn). However, the maximum growth and photosynthetic pigments were observed at the highest concentration of CeO2 NPs (100 mg/L) under elevated CO2. Elevated CO2 resulted in a decreased stomatal conductance (gs) and transpiration rate (Tr), whereas CeO2 NPs enhanced these parameters. No significant changes were observed in any of the measured biochemical parameters due to increased levels of CO2. However, an increase in antioxidant enzymes, particularly in catalase (CAT; 14.37%) and ascorbate peroxidase (APX; 10.66%) activities, was observed in high CeO2 NPs (100 mg/L) treatment under elevated CO2 levels. Regarding plant nutrient content, elevated CO2 significantly decreases spinach roots and leaves macro and micronutrients as compared to ambient CO2 levels. CeO2 NPs, in a dose-dependent manner, with the highest increase observed in 100 mg/L CeO2 NPs treatment and increased roots and shoots magnesium (211.62–215.49%), iron (256.68–322.77%), zinc (225.89–181.49%), copper (21.99–138.09%), potassium (121.46–138.89%), calcium (118.22–91.32%), manganese (133.15–195.02%) under elevated CO2. Overall, CeO2 NPs improved spinach growth and biomass and reverted the adverse effects of elevated CO2 on its nutritional quality. These findings indicated that CeO2 NPs could be used as an effective approach to increase vegetable growth and nutritional values to ensure food security under future climatic conditions.

The role of Aspergillus flavus in modulating the physiological adjustments of sunflower to elevated CO2 and temperature

Exploring the interactions between plants and foliar endophytic fungi under varying climatic conditions is crucial for harnessing endophytes that enhance plant resilience to environmental stressors. This study examines the role of a specific strain of Aspergillus flavus as an endophyte in sunflowers under standard and altered CO2 and temperature regimes. We assessed the impact of this fungus on physiological traits such as chlorophyll and flavonoid content, gas exchange, and Chlorophyll a fluorescence using open-top chambers simulating ambient (∼420 µmol mol−1) and elevated (∼880 µmol mol−1) CO2 levels, along with a temperature increase of 3°C. The findings indicate that A. flavus promotes nitrogen assimilation and chlorophyll production under ambient conditions, potentially enhancing sunflower growth and photosynthetic performance. However, under elevated temperatures (eT), inoculation with A. flavus resulted in decreased biomass and reduced Photosystem II efficiency. Elevated CO2 (eCO2) conditions also led to unexpected negative effects, with reductions in foliar nitrogen, leaf area, and light capture efficiency, culminating in diminished biomass. When both elevated CO2 and temperature conditions were combined (eCO2eT), the interaction further impaired Photosystem II efficiency, suggesting exacerbated physiological stress. These results demonstrate that environmental modifications can transform A. flavus from a beneficial endophyte to a potential pathogen, highlighting the dual nature of plant-fungal interactions. This study underscores the complexity of these relationships under changing climatic conditions and suggests a cautious approach to the agricultural use of endophytes to ensure plant health and productivity.

An Exploration into “Do-It-Yourself” (DIY) CO2 Enrichment Chambers: Utilising Grey Oyster Mushroom (Pleurotus pulmonarius (Fr.) Quél) Respiration to Improve Okra (Abelmoschus esculentus L.) Seedlings Growth

The endeavour to employ CO2 from natural sources to improve plant growth is often challenging, especiallyin tropical climates. While mycelium bags from the mushroom industry can generate CO2, they need indoorconditions with controlled temperature, high humidity, and low light. These conditions are not present inopen fields, leading to low CO2 production. Inspired by the ancient clay evaporative cooling device calledthe zeer pot, a new solution was developed to address this problem. The eventual design was a confinementchamber that housed the mycelium bags and the okra seedlings. The chamber conditions were sufficientlyconducive for the mycelium bags to produce an ambient CO2 level of around 800 ppm during the day. Theresulting okra seedlings under this high CO2 concentration of natural origin had a notable increase in overallbiomass accumulation (+ 277%), carbon assimilation rate (+103%) as well as improved water use efficiency(+95%) compared to seedlings grown under ambient CO2 level. These promising findings not only provedthe capability of mycelium as a natural CO2 generator but also as an additional economic potential for thefarmers to gain income from the CO2-enriched crops as well as the harvested mushroom bodies at the timeof mycelium bags maturity. Furthermore, this simple innovation opens the avenue for furtherinterdisciplinary research in other agricultural efforts to improve crop yield and quality.

Direct foliar phosphorus uptake from wildfire ash

Abstract. Atmospheric particles originating from combustion byproducts (burned biomass or wildfire ash) are highly enriched in nutrients such as P, K, Ca, Mg, Fe, Mn, and Zn. Over long timescales, deposited wildfire ash particles contribute to soil fertility by replenishing soil nutrient reservoirs. However, the immediate nutritional effects of freshly deposited fire ash on plants are mostly unknown. Here, we study the influence of fire ash on plant nutrition by applying ash separately on a plant's foliage or to its substrate around the roots. We conducted experiments on chickpea model plants under ambient and elevated CO2 levels, which reflect current and future climate scenarios. We found that plants can utilize fire ash P and Ni through their leaves by direct nutrient uptake from particles captured on their foliage but not via their roots, both under ambient and elevated CO2 levels. These results indicate that over a short timescale, plants effectively uptake P from fire ash only via the foliage rather than the root pathway, which is possibly due to low bioavailability or limited contact between fire ash particles and the roots. According to many previous studies, elevated levels of CO2 will reduce the ionome of plants due to the partial inhibition of the key root uptake mechanism, thus increasing the significance of foliar nutrient uptake in a future climate. Furthermore, the role of fire ash is expected to increase in the future world, thus giving a competitive advantage to plants that can utilize fire ash P from the foliar pathway, as fire ash P is a particularly efficient and important source of P.

Climate Crisis and Agricultural Response: Climate Resilient Crops for Sustainability in Food Production Systems

Climate change encompasses altered levels of temperature and humidity, variability in the rainfall pattern, fluctuations in weather parameters, rise in ambient CO2 levels, emission of greenhouse gases, global warming, etc. that results in extreme events and disasters as cyclones, floods, droughts, salinity, nutrient and heavy metal stress, change in arthropod diversity and emergence of new invasive pests. This results in un-usual effects in agro-ecosystems leading to changes in cropping patterns, crop diversity, and their interaction with biotic and abiotic stress factors, threatening livelihood, food, and nutritional security. Population displacement, declining food productivity, and vulnerable agro-ecosystems are the major consequences of altered meteorological events that occur due to climate change. Therefore, substitution of traditional crops with crops that exhibit resilience to climate crisis is the need of the hour. Smart breeding approaches and precision farming technologies as remote sensing and spectral analysis, artificial intelligence, machine learning, speed breeding, genome analysis, genetic manipulation, gene drive systems, system biology study, omics approaches, etc can make agricultural production climate resilient and sustainable. Response of biofortified crops under changing climate must also be assessed to improve the crop productivity and output.

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.

Response of Alnus glutinosa to Phytophthora bark infections at ambient and elevated CO2 levels

Response of Alnus glutinosa to Phytophthora bark infections at ambient and elevated CO2 levels

Frequency and Clinical Features of Space Headache Experienced by Astronauts During Long-Haul Space Flights.

Few anecdotal cases and 1 small retrospective study during short-duration space missions suggest that headache may occur early in flight, as part of the space motion syndrome. Whether headaches may also occur at later stages of space flights is unknown. We aimed to prospectively characterize the incidence, timing, clinical features, and management of space headaches during long-duration flights. We prospectively evaluated the occurrence, characteristics, and evolution of space headaches and the effects of treatment and countermeasures during long-haul flights with onboard questionnaires and correlated them with prevailing temperature, pressure, and ambient O2 and CO2 levels, measured within the International Space Station. In addition, we analyzed retrospective headache data from a different astronaut cohort. Headache data were reported using descriptive statistics and correlation data with intraindividual logistic regression models. Astronauts were included through (inter)national aerospace organizations. In the prospective study, 22/24 (91.7%) astronauts (mean ± SD age: 46.6 ± 6.5 years, 95.8% male) experienced ≥1 episode of headache during a total of 3,596 space days. A total of 378 episodes were reported (median 9; range 1-128) with detailed information on 189. Phenotypically, 170/189 (89.9%) episodes were tension-type headache (TTH) and 19/189 (10.1%) were migraine. Episodes in the first week differed from those in later periods in terms of phenotype (migraine 12/51 [23.5%] vs 7/138 [5.1%]; TTH 39/51 [86.5%] vs 131/138 [94.9%]; overall p = 0.0002) and accompanying symptoms: nausea: 17.6% vs 6.9%, p = 0.05; vomiting: 9.8% vs 0.7%, p = 0.005; nasal congestion: 52.9% vs 29.7%, p = 0.004; facial edema: 41.2% vs 1.4%, p < 0.001; and duration (p = 0.001). Severity and treatments were similar: acute antiheadache medication: 55.6%; other medication: 22.4%; and alternative treatments: 41.1%. Headache occurrence was not associated with temperature or ambient pressure/levels of O2 and CO2 (all p > 0.05). In the retrospective study, 23/42 (54.8%) astronauts (43.5 ± 7.2 years, 90.5% male) reported experiencing ≥1 headache episode during mission. Nasal congestion was the most common (8/33; 24.2%) accompanying symptom. Seventeen of 42 astronauts have been previously described. Astronauts during space flights frequently experience headaches. These most often have characteristics of TTHs but sometimes have migrainous features, particularly during the first week of flight in astronauts without a history of recurrent headaches before or after the space flight.

Elevated Ambient Carbon Dioxide Levels Induce Attraction but Not Attachment of Adult Ixodes scapularis in Artificial Membrane Feeding

Numerous feeding studies on tick species have explored disease transmission, vector interactions, and acaricide testing. Traditionally, these studies used animals for feeding. However, artificial membrane feeding offers several advantages including increased standardization of experiments, decreased costs, and improved animal welfare. In vitro conditions must closely mimic natural environments to promote successful feeding attachment. Kairomones produced by the host are strong stimulants that encourage attachment. An important kairomone detected by ticks is carbon dioxide (CO2). Previous studies have shown elevated CO2 levels stimulate host identification and attraction and potentially improve artificial feeding rates in some tick species. The objective of this study was to use an artificial membrane feeding chamber prototype to explore the effects of ambient CO2 in inducing Ixodes scapularis attachment. Differences in attachment rate were explored at an air-typical ambient CO2 level of 0.04% and an elevated CO2 level of 4.0%. Tick attachment was not detected in either ambient CO2 condition during the incubation period, indicating ambient CO2 does not impact the attachment rate under the presented condition. However, I. scapularis contact with the artificial membrane occurred at an increased rate of 0.014 female ticks in contact with the membrane per hour in the elevated CO2 condition (4%) compared with a rate of 0.01 ticks per hour in the air-typical CO2 condition (0.04%) (p = 0.048) suggesting that the ambient CO2 level affects attraction to the blood but does not directly stimulate attachment of I. scapularis.

Ventilation during COVID-19 in a school for students with intellectual and developmental disabilities (IDD).

This study examined the correlation of classroom ventilation (air exchanges per hour (ACH)) and exposure to CO2 ≥1,000 ppm with the incidence of SARS-CoV-2 over a 20-month period in a specialized school for students with intellectual and developmental disabilities (IDD). These students were at a higher risk of respiratory infection from SARS-CoV-2 due to challenges in tolerating mitigation measures (e.g. masking). One in-school measure proposed to help mitigate the risk of SARS-CoV-2 infection in schools is increased ventilation. We established a community-engaged research partnership between the University of Rochester and the Mary Cariola Center school for students with IDD. Ambient CO2 levels were measured in 100 school rooms, and air changes per hour (ACH) were calculated. The number of SARS-CoV-2 cases for each room was collected over 20 months. 97% of rooms had an estimated ACH ≤4.0, with 7% having CO2 levels ≥2,000 ppm for up to 3 hours per school day. A statistically significant correlation was found between the time that a room had CO2 levels ≥1,000 ppm and SARS-CoV-2 PCR tests normalized to room occupancy, accounting for 43% of the variance. No statistically significant correlation was found for room ACH and per-room SARS-CoV-2 cases. Rooms with ventilation systems using MERV-13 filters had lower SARS-CoV-2-positive PCR counts. These findings led to ongoing efforts to upgrade the ventilation systems in this community-engaged research project. There was a statistically significant correlation between the total time of room CO2 concentrations ≥1,000 and SARS-CoV-2 cases in an IDD school. Merv-13 filters appear to decrease the incidence of SARS-CoV-2 infection. This research partnership identified areas for improving in-school ventilation.

A laboratory study of the increasing competitiveness of Karenia mikimotoi under rising CO2 scenario

Ocean acidification (OA) driven by elevated carbon dioxide (CO2) levels is expected to disturb marine ecological processes, including the formation and control of harmful algal blooms (HABs). In this study, the effects of rising CO2 on the allelopathic effects of macroalgae Ulva pertusa to a toxic dinoflagellate Karenia mikimotoi were investigated. It was found that high level of CO2 (1000 ppmv) promoted the competitive growth of K. mikimotoi compared to the group of present ambient CO2 level (420ppmv), with the number of algal cell increased from 32.2 × 104 cells/mL to 36.75 × 104 cells/mL after 96 h mono-culture. Additionally, rising CO2 level weakened allelopathic effects of U. pertusa on K. mikimotoi, as demonstrated by the decreased inhibition rate (50.6 % under the original condition VS 34.3 % under the acidified condition after 96 h co-culture) and the decreased reactive oxygen species (ROS) level, malondialdehyde (MDA) content, antioxidant enzymes activity (superoxide dismutase (SOD), peroxidase (POD), glutathione peroxidase (GPX), glutathione reductase (GR) and catalase (CAT) and non-enzymatic antioxidants (glutathione (GSH) and ascorbic acid (ascorbate, vitamin C). Indicators for cell apoptosis of K. mikimotoi including decreased caspase-3 and -9 protease activity were observed when the co-cultured systems were under rising CO2 exposure. Furthermore, high CO2 level disturbed fatty acid synthesis in U. pertusa and significantly decreased the contents of fatty acids with allelopathy, resulting in the allelopathy weakening of U. pertusa. Collectively, rising CO2 level promoted the growth of K. mikimotoi and weakened allelopathic effects of U. pertusa on K. mikimotoi, indicating the increased difficulties in controlling K. mikimotoi using macroalgae in the future.

Direct Exposure to Outdoor Air Pollution Worsens the Functional Status of Stroke Patients Treated with Mechanical Thrombectomy

Background The effect of air pollutants on the functional status of stroke patients in short-term follow-up is unknown. The aim of this study was to evaluate the effect of air pollution occurring in the stroke period and during hospitalization on the functional status of patients undergoing mechanical thrombectomy (MT). Methods Our study included stroke patients for which the individual-level exposure to ambient levels of O3, CO, SO2, NO2, PM2.5, and PM10 during the acute stroke period was assessed. The correlations between the air pollutants’ concentration and the patients’ functional state were analyzed. A total of 499 stroke patients (mean age: 70) were qualified. Results The CO concentration at day of stroke onset was found to be significant regarding the functional state of patients on the 10th day (OR 0.014 95% CI 0–0.908, p = 0.048). The parameters which increased the risk of death in the first 10 days were as follows: NIHSS (OR 1.27; 95% CI 1.15–1.42; p &lt; 0.001), intracranial bleeding (OR 4.08; 95% CI 1.75–9.76; p = 0.001), and SO2 concentration on day 2 (OR 1.21; 95% CI 1.02–1.47; p = 0.03). The parameters which increased the mortality rate within 90 days include age (OR 1.07; 95% CI 1.02–1.13; p = 0.005) and NIHSS (OR 1.37; 95% CI 1.19–1.63; p &lt; 0.001). Conclusions Exposure to air pollution with CO and SO2 during the acute stroke phase has adverse effects on the patients’ functional status. A combination of parameters, such as neurological state, hemorrhagic transformation, and SO2 exposure, is unfavorable in terms of the risk of death during a hospitalization due to stroke. The risk of a worsened functional status of patients in the first month of stroke rises along with the increase in particulate matter concentrations within the first days of stroke.

How Nutrients Mediate the Impacts of Global Change on Locust Outbreaks.

Locusts are grasshoppers that can migrate en masse and devastate food security. Plant nutrient content is a key variable influencing population dynamics, but the relationship is not straightforward. For an herbivore, plant quality depends not only on the balance of nutrients and antinutrients in plant tissues, which is influenced by land use and climate change, but also on the nutritional state and demands of the herbivore, as well as its capacity to extract nutrients from host plants. In contrast to the concept of a positive relationship between nitrogen or protein concentration and herbivore performance, a five-decade review of lab and field studies indicates that equating plant N to plant quality is misleading because grasshoppers respond negatively or neutrally to increasing plant N just as often as they respond positively. For locusts specifically, low-N environments are actually beneficial because they supply high energy rates that support migration. Therefore, intensive land use, such as continuous grazing or cropping, and elevated ambient CO2 levels that decrease the protein:carbohydrate ratios of plants are predicted to broadly promote locust outbreaks.

Generation of Mature Toxoplasma gondii Bradyzoites in Human Immortalized Myogenic KD3 Cells.

Toxoplasma gondii is a zoonotic protozoan parasite and one of the most successful foodborne pathogens. Upon infection and dissemination, the parasites convert into the persisting, chronic form called bradyzoites, which reside within cysts in muscle and brain tissue. Despite their importance, bradyzoites remain difficult to investigate directly, owing to limited in vitro models. In addition, the need for new drugs targeting the chronic stage, which is underlined by the lack of eradicating treatment options, remains difficult to address since in vitro access to drug-tolerant bradyzoites remains limited. We recently published the use of a human myotube-based bradyzoite cell culture system and demonstrated its applicability to investigate the biology of T. gondii bradyzoites. Encysted parasites can be functionally matured during long-term cultivation in these immortalized cells and possess many in vivo-like features, including pepsin resistance, oral infectivity, and antifolate resistance. In addition, the system is scalable, enabling experimental approaches that rely on large numbers, such as metabolomics. In short, we detail the cultivation of terminally differentiated human myotubes and their subsequent infection with tachyzoites, which then mature to encysted bradyzoites within four weeks at ambient CO2 levels. We also discuss critical aspects of the procedure and suggest improvements. Key features • This protocol describes a scalable human myotube-based in vitro system capable of generating encysted bradyzoites featuring in vivo hallmarks. • Bradyzoite differentiation is facilitated through CO2 depletion but without additional artificial stress factors like alkaline pH. • Functional maturation occurs over four weeks.

Elevated carbon dioxide concentrations increase the risk of Cd exposure in rice.

Since the Industrial Revolution, crops have been exposed to various changes in the environment, including elevated atmospheric carbon dioxide (CO2) concentration and cadmium (Cd) pollution in soil. However, information about how combined changes affect crop is limited. Here, we have investigated the changes of japonica and indica rice subspecies seedlings under elevated CO2 level (1200 ppm) and Cd exposure (5 μM Cd) conditions compared with ambient CO2 level (400 ppm) and without Cd exposure in CO2 growth chambers with hydroponic experiment. The results showed that elevated CO2 levels significantly promoted seedling growth and rescued the growth inhibition under Cd stress. However, the elevated CO2 levels led to a significant increase in the shoot Cd accumulation of the two rice subspecies. Especially, the increase of shoot Cd accumulation in indica rice was more than 50% compared with control. Further investigation revealed that the decreases in the photosynthetic pigments and photosynthetic rates caused by Cd were attenuated by the elevated CO2 levels. In addition, elevated CO2 levels increased the non-enzymatic antioxidants and significantly enhanced the ascorbate peroxidase (APX) and glutathione reductase (GR) activities, alleviating the lipid peroxidation and reactive oxygen species (ROS) accumulation induced by Cd. Overall, the research revealed how rice responded to the elevated CO2 levels and Cd exposure, which can help modify agricultural practices to ensure food security and food safety in a future high-CO2 world.

Calcium ammonium nitrate applications for improved leaf growth and photosynthetic responses in the CAM orchid Phalaenopsis under elevated CO2 in a greenhouse

Phalaenopsis Queen Beer ‘Mantefon’ is an orchid species that absorbs CO2 at nighttime due to its crassulacean acid metabolism. These orchids originated from nutrient–poor environments in tropical forest understories. However, elevated CO2 at nighttime influences plant nitrogen utilization for growth. This study investigated the leaf growth and photosynthetic responses in Phalaenopsis Queen Beer ‘Mantefon’ to varying ambient and elevated CO2 (400 and 800 μmol⋅mol−1, respectively) and four nitrogen−based calcium ammonium nitrate (CAN) levels over 20 weeks: calcium, ammonium, and nitrate levels by 0.00, 0.00, and 0.00 mmol⋅L−1 (CAN0, control), 0.90, 0.55, and 2.97 mmol⋅L−1 (CAN1), 6.73, 1.11, and 6.05 mmol⋅L−1 (CAN2), and 12.80, 1.72, and 9.13 mmol⋅L−1 (CAN3), respectively. The phosphate and potassium levels were consistent across all CAN levels at 2.74 and 4.37 mmol⋅L−1, respectively. Elevated CO2 levels showed no significant impact on the number of leaves in CAN1−3 plants yet increased with those with CAN0. Leaf area significantly increased with elevated CO2 levels by 44 % (CAN0) and 26 % (CAN1). Strong correlations emerged between the number of leaves and leaf area, as well as between leaf area and root−to−shoot dry biomass ratio (R/S). Increasing CO2 levels heightened SPAD chlorophyll in CAN0 plants, and SPAD and F0 showed a strong correlation with elevated CO2 and increasing CAN levels. The total dry biomass decreased in plants with high CAN (CAN and CAN3) compared to those with CAN0, regardless of CO2 levels, and Fv/Fm dropped below 0.616 with high CAN under elevated CO2. Phalaenopsis Queen Beer ‘Mantefon’ demonstrated augmented leaf growth and R/S under limited CAN (CAN0) and elevated CO2 conditions, indicating improved resource allocation potential. The results suggest that supplying CO2 in a greenhouse can effectively improve Phalaenopsis vegetative growth with limited nutrient conditions, which differs from growth aspects under ambient CO2 levels.

Boreal conifers maintain carbon uptake with warming despite failure to track optimal temperatures

Warming shifts the thermal optimum of net photosynthesis (ToptA) to higher temperatures. However, our knowledge of this shift is mainly derived from seedlings grown in greenhouses under ambient atmospheric carbon dioxide (CO2) conditions. It is unclear whether shifts in ToptA of field-grown trees will keep pace with the temperatures predicted for the 21st century under elevated atmospheric CO2 concentrations. Here, using a whole-ecosystem warming controlled experiment under either ambient or elevated CO2 levels, we show that ToptA of mature boreal conifers increased with warming. However, shifts in ToptA did not keep pace with warming as ToptA only increased by 0.26–0.35 °C per 1 °C of warming. Net photosynthetic rates estimated at the mean growth temperature increased with warming in elevated CO2 spruce, while remaining constant in ambient CO2 spruce and in both ambient CO2 and elevated CO2 tamarack with warming. Although shifts in ToptA of these two species are insufficient to keep pace with warming, these boreal conifers can thermally acclimate photosynthesis to maintain carbon uptake in future air temperatures.

The interaction of O3 and CO2 concentration, exposure timing and duration on stem rust severity on winter wheat variety ‘Coker 9553’

Wheat rusts, elevated ozone (O3), and carbon dioxide (CO2) are simultaneously impacting wheat production worldwide, but their interactions are not well understood. This study investigated whether near-ambient O3 is suppressive or conducive to stem rust (Sr) of wheat, considering the interactions with ambient and elevated CO2.Winter wheat variety ‘Coker 9553’ (Sr-susceptible; O3 sensitive) was inoculated with Sr (race QFCSC) following pre-treatment with four different concentrations of O3 (CF, 50, 70, and 90 ppbv) at ambient CO2 levels. Gas treatments were continued during the development of disease symptoms. Disease severity, measured as percent sporulation area (PSA), significantly increased relative to the CF control only under near-ambient O3 conditions (50 ppbv) in the absence of O3-induced foliar injury. Disease symptoms at higher O3 exposures (70 and 90 ppbv) were similar to or less than the CF control. When Coker 9553 was inoculated with Sr while exposed to CO2 (400; 570 ppmv) and O3 (CF; 50 ppbv) in four different combinations, and seven combinations of exposure timing and duration, PSA significantly increased only under continuous treatment with O3 for six weeks or pre-inoculation treatment for three weeks, suggesting that O3-predisposes wheat to the disease rather than enhancing disease post-inoculation. O3 singly and in combination with CO2 increased PSA on flag leaves of adult Coker 9553 plants while elevated CO2 alone had little effect on PSA.These findings show that sub-symptomatic O3 conditions are conducive to stem rust, contradicting the current consensus that biotrophic pathogens are suppressed by elevated O3. This suggests that sub-symptomatic O3 stress may enhance rust diseases in wheat-growing regions.

Arabidopsis stromal carbonic anhydrases exhibit non-overlapping roles in photosynthetic efficiency and development.

Carbonic anhydrases (CAs) are ubiquitous enzymes that accelerate the reversible conversion of CO2 to HCO3 - . The Arabidopsis genome encodes members of the α-, β- and γ-CA families, and it has been hypothesized that βCA activity has a role in photosynthesis. In this work, we tested this hypothesis by characterizing the two plastidial βCAs, βCA1and βCA5, in physiological conditions of growth. We conclusively established that both proteins are localized in the chloroplast stroma and that the loss of βCA5 induced the expression of βCA1, supporting the existence of regulatory mechanisms to control the expression of stromal βCAs. We also established that βCA1 and βCA5 have markedly different enzymatic kinetics and physiological relevance. Specifically, we found that βCA5 had a first-order rate constant ~10-fold lower than βCA1, and that the loss of βCA5 is detrimental to growth and could be rescued by high CO2 . Furthermore, we established that, while a βCA1 mutation showed near wild-type growth and no significant impact on photosynthetic efficiency, the loss of βCA5 markedly disrupted photosynthetic efficiency and light-harvesting capacity at ambient CO2 . Therefore, we conclude that in physiological autotrophic growth, the loss of the more highly expressed βCA1 does not compensate for the loss of a less active βCA5, which in turn is involved in growth and photosynthesis at ambient CO2 levels. These results lend support to the hypothesis that, in Arabidopsis,βCAs have non-overlapping roles in photosynthesis and identify a critical activity of stromal βCA5 and a dispensable role for βCA1.