Control CO2 Levels Research Articles

Multi-spatial Resolution Imagery to Estimate Above-Ground Carbon Stocks in Mangrove Forests

Mangroves are a type of vegetation that can absorb carbon and have an essential role in controlling CO2 levels in the atmosphere. Mangroves can absorb carbon better than terrestrial ecosystems because of their ability to bury carbon in sediment. This research aims to compare and measure the carbon stock content above the surface of mangroves in the field using multi-spatial resolution imagery, namely, Landsat 8 OLI, Sentinel 2A, and Planetscope. Field carbon calculations were carried out using the allometric method based on mangrove species. The calculation results are then linked through regression analysis with the vegetation index Difference Vegetation Index (DVI) results. The total carbon obtained from PlanetScope imagery was 535.27 tons, Sentinel 2A imagery was 549.23 tons, and Landsat 8 OLI imagery was 533.57 tons. Among the three images used, based on Sentinel 2A statistical analysis reflects the possibility of overfitting or the best with higher r and R2 values in the calculations. However, based on SE accuracy tests, PlanetScope has better accuracy than the other two images. Apart from that, the accuracy test results using a 1:1 goodness of fit plot for each image, the distribution pattern of mangrove carbon stock estimates shows that the entire model in mapping mangrove carbon stocks is over-estimated. The overestimated results are possible because more objects around the mangrove, especially canopy density, are recorded by remote sensing sensors compared to tree diameter as input for field carbon results.

Validation of a CFD model for cell culture bioreactors at large scale and its application in scale-up

Among all the operating parameters that control the cell culture environment inside bioreactors, appropriate mixing and aeration are crucial to ensure sufficient oxygen supply, homogeneous mixing, and CO2 stripping. A model-based manufacturing facility fit approach was applied to define agitation and bottom air flow rates during the process scale-up from laboratory to manufacturing, of which computational fluid dynamics (CFD) was the core modeling tool. The realizable k-ε turbulent dispersed Eulerian gas-liquid flow model was established and validated using experimental values for the volumetric oxygen transfer coefficient (kLa). Model validation defined the process operating parameter ranges for application of the model, identified mixing issues (e.g., impeller flooding, dissolved oxygen gradients, etc.) and the impact of antifoam on kLa. Using the CFD simulation results as inputs to the models for oxygen demand, gas entrance velocity, and CO2 stripping aided in the design of the agitation and bottom air flow rates needed to meet cellular oxygen demand, control CO2 levels, mitigate risks for cell damage due to shear, foaming, as well as fire hazards due to high O2 levels in the bioreactor gas outlet. The recommended operating conditions led to the completion of five manufacturing runs with a 100% success rate. This model-based approach achieved a seamless scale-up and reduced the required number of at-scale development batches, resulting in cost and time savings of a cell culture commercialization process.

Net CO2 assimilation rate response of tomato seedlings (Solanum lycopersicum L.) to the interaction between light intensity, spectrum and ambient CO2 concentration.

Artificial lighting is complementary and single-source lighting for controlled Environment Agriculture (CEA) to increase crop productivity. Installations to control CO2 levels and luminaires with variable spectrum and intensity are becoming increasingly common. In order to see the net assimilation of CO2 based on the relationship between the three factors: intensity, spectrum and CO2 concentration, tests are proposed on tomatoes seedling with combinations of ten spectra (100B, 80B20G, 20B80G, 100G, 80G20R, 20G80R, 100R, 80R20B, 20R80B, 37R36G27B) seven light intensities (30, 90, 200, 350, 500, 700 and 1000 μmol·m-2 s-1) and nine CO2 concentrations (200, 300, 400, 500, 600, 700, 800 and 900 ppm). These tomato seedlings grew under uniform conditions with no treatments applied up to the moment of measurement by a differential gas analyzer. We have developed a model to evaluate and determine under what spectrum and intensity of light photosynthesis the Net assimilation of CO2 (An) is more significant in the leaves of tomato plants, considering the CO2 concentration as an independent variable in the model. The evaluation of the model parameters for each spectrum and intensity shows that the intensity has a more decisive influence on the maximum An rate than the spectra. For intensities lower than 350 μmol·m-2 s-1, it is observed that the spectrum has a greater influence on the variable An. The spectra with the best behaviour were 80R20B and 80B20R, which maintained An values between 2 and 4 (μmol CO2·m-2·s-1) above the spectra with the worst behaviour (100G, 80G20R, 20G80R and 37B36G27R) in practically all situations. Photosynthetic Light-Use Efficiency (PLUE) was also higher for the 80B20R and 20R80B spectra with values of 36,07 and 33,84 mmol CO2·mol photon-1, respectively, for light intensities of 200 μmol·m-2 s-1 and 400 ppm of CO2that increased to values of 49,65 and 48,38 mmol CO2·mol photon-1 for the same light intensity and concentrations of 850 ppm. The choice of spectrum is essential, as indicated by the data from this study, to optimize the photosynthesis of the plant species grown in the plant factory where light intensities are adjusted for greater profitability.

Short-term exposure to near-future CO2has limited influence on the energetics and behaviour of young-of-year salmonids

In many freshwater ecosystems, carbon dioxide (CO2) is increasing. Unknown are the risks that high CO2poses for freshwater organisms, especially fish. The objective of this study was to determine how CO2may influence the growth rate, metabolic rate, feeding rate, and volitional behaviour of young-of-year Arctic charr ( Salvelinus alpinus (Linnaeus, 1758)), brook charr ( Salvelinus fontinalis (Mitchill, 1814)), and rainbow trout ( Oncorhynchus mykiss (Walbaum, 1792)). For this study, fish stayed in control (1100 microatmospheres (µatm)) or elevated (5236 µatm) CO2levels for 15 days. During this time, metabolic rate and behavioural tests were conducted on alternating days for each treatment. Weight and length of each fish were taken on days 0, 7, and 15. There was no evidence that elevated CO2affected the growth rate, feeding rate, or behaviour in any of these species. The standard metabolic rate in Arctic charr differed based on CO2exposure. Therefore, salmonids can withstand short periods of elevated CO2under these conditions. By comparing closely related species, the implications of this work are more ecologically relevant and will also help industry quantify the effects of high CO2on young salmonids.

CO2 fixation mechanism of kaolin treated with organic amines at varied temperatures and pressure

CO2 capture and storage is an effective way to control CO2 levels in the atmosphere. However, the adsorption technology is determined by many factors, such as temperature, pressure, and material cost. In this study, a clay-based CO2 adsorbent was designed to monitor the possible factors that affect the geological condensation of CO2 under varied conditions. The effect of molecular chain length on the CO2 adsorption performance of intercalated kaolinite was discussed in detail. The prepared kaolinite/n-hexylamine complex achieved a 17.0 (±0.4) mL/g CO2 adsorption capacity when 6.35% (±0.05) n-hexylamine was loaded, which has significantly improved the utilization rate of organic amines. A higher relative CO2 adsorption capacity (in proportion to the amount of amine) was obtained at lower temperatures and higher pressures. The mechanism of CO2 adsorption of organic amine-intercalated kaolinite was discussed based on Fourier transform infrared spectroscopy and specific surface area measurements. The enhanced relative CO2 adsorption capacity at low-temperature and high-pressure conditions may provide a hint to the geological condensation of CO2 at high latitude positions.

Comparison of vegetation indices for estimating above-ground mangrove carbon stocks using PlanetScope image

Mangroves play a pivotal role in providing ecological benefits and services to reduce and adapt to climate change impact on coastal ecosystem. They are capable of absorbing carbon, which is crucial in controlling CO2 levels in the atmosphere. This research aims to assess the accuracy of selected vegetation indices for estimating above-ground carbon (AGC) stocks of mangroves using PlanetScope images in Bedul, Banyuwangi, East Java Province, Indonesia. A semi-empirical approach was used to assess and map mangrove AGC, starting with applying the allometric equation to calculate field-measured species-specific AGC stocks. Regression analyses were applied to develop a relationship between field AGC and vegetation indices derived from PlanetScope Image, including Normalized Difference Vegetation Index (NDVI), Difference Vegetation Index (DVI), and Enhanced Vegetation Index (EVI). The Standard Errors of Estimates (SE) were 31.41, 32.93, and 31.63 tons/ha for DVI, EVI, and NDVI, respectively. Thus, carbon stocks estimation, including DVI as an independent variable, is considered more accurate than other vegetation indices tested in this research

And Lung Function: An in Vivo Exploration of Potential Climate Change Implications.

Vol. 129, No. 3 Science SelectionOpen AccessCO2 and Lung Function: An in Vivo Exploration of Potential Climate Change Implicationsis accompanied byMouse Lung Structure and Function after Long-Term Exposure to an Atmospheric Carbon Dioxide Level Predicted by Climate Change Modeling Florencia Pascual Florencia Pascual Search for more papers by this author Published:22 March 2021CID: 034002https://doi.org/10.1289/EHP8975AboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmail AbstractAtmospheric carbon dioxide (CO2) hit a milestone in 2015, when global average concentrations reached 400ppm for the first time in recorded history.1 By 2100, the global average could more than double if emissions remain unabated, according to the RCP8.5 (“business as usual”) scenario used by the Intergovernmental Panel on Climate Change in its assessments.2 Although much attention has been paid to the effect of CO2 as a climate forcing agent, multiple reports suggest this greenhouse gas also may have direct health effects.3 A recent report in Environmental Health Perspectives used a mouse model to assess the pulmonary effects of chronic exposure to ambient CO2 at concentrations comparable to those projected by climate modeling.4Humans have been exposed to atmospheric CO2 concentrations averaging roughly 230ppm since the time of our earliest ancestor.9,10 However, intensified human activity and associated CO2 emissions have led to increases of 2–3ppm per year for the past 50 years. In its most recent update as of this writing, Hawaii’s Mauna Loa Observatory reported a seasonally adjusted CO2 concentration of 414.88ppm for the month of December 2020.11 Image: National Aeronautics and Space Administration. Based on data from Lüthi et al. (2008).12A 2019 review in Nature Sustainability summarized evidence on the effects on lung function of very high (>1,000ppm), acute CO2 exposures.3 In contrast, current report is the first known study to directly assess the physiological impact of long-term exposure to CO2 concentrations that are realistically possible in the near future, says first author Alexander Larcombe, an associate professor at the Telethon Kids Institute and Wal-yan Respiratory Research Center in Nedlands, Australia.In the new study, investigators exposed adult female mice and their offspring to either control (approximately 465ppm) or elevated (approximately 890ppm) concentrations of CO2. Dams began exposure with a 1-week acclimation period before mating, and offspring were exposed from preconception to adulthood. At postnatal week 12, the investigators assessed the offspring’s respiratory function and lung structure. To compare the effects of exposure during lung development versus exposure during adulthood, they also examined the dams’ lung function.Their results indicate that, among female offspring, exposures to high ambient CO2 caused modest measurable changes in lung function and structure compared with exposure to control CO2 levels. The fact that deficits were seen only in offspring suggests the differences were developmental rather than adaptational.Lung development impairment is well documented to occur in a low-oxygen environment (hypoxia);5 however, the exposure model used in this study did not mimic hypoxic conditions, where oxygen levels are significantly lower while CO2 levels remain unchanged. In the lung, gas exchange occurs in tiny air sacs called alveoli, and perturbations in ambient CO2 levels would be expected to result in increased lung area through alveolarization,6 which in the mouse develops almost exclusively after birth.7 Consistent with this notion, male mice exhibited higher numbers of alveoli; conversely, females showed decreased alveolarization. Other markers of lung function suggested that high CO2 exposure affected female mice exclusively.The authors proposed respiratory acidosis, a change in blood chemistry that results from CO2 exposure, as a possible basis for impaired lung function in female mice. However, they explored no foundation for the sex-specific effects.The findings reported by the authors might not rule out an effect on male mice given the relatively small sample size and inherent animal-to-animal variability, cautions Darryl Zeldin, head of the Environmental Cardiopulmonary Disease Group and scientific director of the National Institute of Environmental Health Sciences. Zeldin was not involved in the study.An additional caveat to the study is the choice of animal model. As burrowing animals, mice are more tolerant to elevated CO2 than animals that stay aboveground.8 Larcombe suggests that future studies should address whether similar outcomes occur in larger, nonburrowing mammals, which would help to give further insight into potential implications for human health.Florencia Pascual, PhD, is a Durham, NC–based freelance science writer.

Using microcontrollers and sensors to build an inexpensive CO2 control system for growth chambers.

PREMISEA CO2 control system is important for investigating how elevated CO2 affects plant growth. Our automatic CO2 monitoring and control system offers an inexpensive and flexible way to make CO2‐enriched environments.METHOD AND RESULTSUsing microcontrollers paired with non‐dispersive infrared CO2 sensors, relays, and valves, we developed a low‐cost system for monitoring and controlling CO2 levels in growth chambers.CONCLUSIONSCompared with existing commercially available CO2 control systems, Arduino‐based microcontrollers offer affordable access to the data logging of CO2 levels in growth chambers, thereby reducing budget limitations for creating growth conditions with highly controlled CO2 concentrations.

Elevated pCO2 Affects Feeding Behavior and Acute Physiological Response of the Brown Crab Cancer pagurus.

Anthropogenic climate change exposes marine organisms to CO2 induced ocean acidification (OA). Marine animals may make physiological and behavioral adaptations to cope with OA. Elevated pCO2 may affect metabolism, feeding, and energy partition of marine crabs, and thereby affect their predator-prey dynamics with mussels. Therefore, we examined the effects of simulated future elevated pCO2 on feeding behavior and energy metabolism of the brown crab Cancer pagurus. Following 54 days of pre-acclimation to control CO2 levels (360 μatm) at 11°C, crabs were exposed to consecutively increased oceanic CO2 levels (2 weeks for 1200 and 2300 μatm, respectively) and subsequently returned to control CO2 level (390 μatm) for 2 weeks in order to study their potential to acclimate elevated pCO2 and recovery performance. Standard metabolic rate (SMR), specific dynamic action (SDA) and feeding behavior of the crabs were investigated during each experimental period. Compared to the initial control CO2 conditions, the SMRs of CO2 exposed crabs were not significantly increased, but increased significantly when the crabs were returned to normal CO2 levels. Conversely, SDA was significantly reduced under high CO2 and did not return to control levels during recovery. Under high CO2, crabs fed on smaller sized mussels than under control CO2; food consumption rates were reduced; foraging parameters such as searching time, time to break the prey, eating time, and handling time were all significantly longer than under control CO2, and prey profitability was significantly lower than that under control conditions. Again, a two-week recovery period was not sufficient for feeding behavior to return to control values. PCA results revealed a positive relationship between feeding/SDA and pH, but negative relationships between the length of foraging periods and pH. In conclusion, elevated pCO2 caused crab metabolic rate to increase at the expense of SDA. Elevated pCO2 affected feeding performance negatively and prolonged foraging periods. These results are discussed in the context of how elevated pCO2 may impair the competitiveness of brown crabs in benthic communities.

Irreversible behavioural impairment of fish starts early: Embryonic exposure to ocean acidification

Long-term species responses to ocean acidification depend on their sensitivity during different life stages. We tested for sensitivity of juvenile fish behaviour to ocean acidification by exposing eggs to control and elevated CO2 levels, and translocating offspring between treatments in a reciprocal design. After 12 weeks of exposure, activity, inactivity and anxiety levels of juveniles from control eggs were similar, whether juveniles had experienced elevated CO2 conditions or not, and this pattern was consistent over time. However, juveniles raised as eggs under elevated CO2 showed increased anxiety levels compared to those from control eggs. This response was not reversed when CO2-exposed juveniles were translocated to control conditions. Our findings highlight the value of evaluating fish sensitivities to global change pollutants across different life stages, and indicate that sensitivity during the often-overlooked egg stage can be critical with long-lasting impairment of behaviours that are coupled to individual fitness and population persistence.

Mechanisms of elevation-dependent warming over the Tibetan plateau in quadrupled CO2 experiments

Observations have shown that the Tibetan Plateau (TP) has experienced elevation-dependent warming (EDW) during recent decades, that is, greater warming at higher elevations than at lower elevations. However, the factors and their mechanisms driving these changes remain unclear, due to scarce radiation-related observations. In the present study, four CCSM3 experiments using the 1990 control and quadrupled (4×) CO2 levels, with fine and coarse resolutions, were examined to shed light on the mechanisms driving EDW. The differences in annual and seasonal surface temperatures (TS) between the 4× CO2 and 1990 control runs, using T85 resolution, feature clear changes with elevation. In addition, EDW 500 m above the ground surface is much weaker and almost disappears at the surface elevations higher than 2000 m. This implies that the greater warming mainly occurs at the near surface with higher elevations and should be attributed to changes in the surface energy budget. In the 4× CO2, there are greater increases (compared to the 1990 control run) in the net solar, net longwave and sensible heat fluxes at the surface at higher elevations, but lower levels of the parameters are simulated at lower elevations. These differences lead to increases in the heat storage at the surface and finally result in greater warming at higher elevations. Compared with the net longwave flux, the relative net shortwave flux at the surface increases more evidently at higher elevations, implying that the increase in net shortwave flux at the surface plays a dominant role in producing greater warming at higher elevations. The elevation range between 2000 and 3000 m appears to be a turning point; below 2000 m, the total cloud increases and subsequently constrains the surface net solar radiation. Above 3000 m, the total cloud decreases but shows little elevation dependency, favoring the increases in the surface net solar radiation, and decreases in the snow depth, with more differences with increasing elevation, lead to the reduced surface albedo. This further facilitates the absorption of solar radiation at higher elevations. Therefore, the combined effects of changes in the snow depth and cloud cover in response to 4× CO2 levels result in greater heat storage at the surface at higher elevations than at lower elevations, leading to EDW over and around the TP.

Effect of ocean acidification on the early life stages of clingfish, Lepadogaster lepadogaster

Event Abstract Back to Event Effect of ocean acidification on the early life stages of clingfish, Lepadogaster lepadogaster Sara Martins1, Ana F. Lopes1, Emanuel J. Gonçalves1 and Ana M. Faria1* 1 MARE ISPA, Portugal Ocean acidification, caused by elevated levels of atmospheric carbon dioxide (CO2), is recognized as a serious threat to marine ecosystems. Most studies have focused on marine calcifying organisms, due to their dependence on calcium carbonate, and less attention has been given to fish. However, recent studies on the early life stages of fishes suggest that behavior, growth, development and otolith size may be highly affected by ocean acidification. Other studies fail to find any detectable effect of exposure to high CO2 levels. These contradictory results suggest species-specific sensitivities to increasing concentrations of CO2 and point to a need of further research on phylogenetically diverse species. In this study we tested the effects of CO2-induced ocean acidification on the early life stages of a temperate marine fish, the clingfish Lepadogaster lepadogaster, by rearing larvae since hatching in control and high pCO2 conditions. Size-at-age metrics and otolith size were examined in pre-settlement stage larvae. Additionally, the behavioural response to a predator odour was tested, as is key behavior to predator avoidance and survival, and is one of the most commonly affected behaviors in marine fishes exposed to high CO2 levels. Larvae in the acidified treatment tended to be slightly larger than fish reared at control CO2 levels, but effects weren’t statistically significant. Exposure to high CO2 did not affect olfactory preferences either. These results suggest that early life stages of clingfish might be resilient to future scenarios of ocean acidification. Clingfish is a benthic spawner that inhabit the intertidal rock pools, which is a habitat with considerable short term natural variation in pH, and may thus be expected to show some tolerance to varying CO2 levels. Acknowledgements This work was supported by a post-doc grant (SFRH/BPD/68673/2010), project ACIDLARVAE (PTDC/MAR-EST/4627/2012) and through the strategic project (UID/MAR/04292/2013) granted to MARE, all financed by Fundação para a Ciência e a Tecnologia. Keywords: ocean acidification, cling fish, larval development, otolith, Olfactory preference Conference: IMMR | International Meeting on Marine Research 2016, Peniche, Portugal, 14 Jul - 15 Jul, 2016. Presentation Type: Poster presentation Topic: Biodiversity, Conservation and Coastal Management Citation: Martins S, Lopes AF, Gonçalves EJ and Faria AM (2016). Effect of ocean acidification on the early life stages of clingfish, Lepadogaster lepadogaster . Front. Mar. Sci. Conference Abstract: IMMR | International Meeting on Marine Research 2016. doi: 10.3389/conf.FMARS.2016.04.00096 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 03 May 2016; Published Online: 13 Jul 2016. * Correspondence: PhD. Ana M Faria, MARE ISPA, Lisboa, 1149-041, Portugal, AFaria@ispa.pt Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Sara Martins Ana F Lopes Emanuel J Gonçalves Ana M Faria Google Sara Martins Ana F Lopes Emanuel J Gonçalves Ana M Faria Google Scholar Sara Martins Ana F Lopes Emanuel J Gonçalves Ana M Faria PubMed Sara Martins Ana F Lopes Emanuel J Gonçalves Ana M Faria Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Impact of ocean acidification on thermal tolerance and acid–base regulation of Mytilus edulis (L.) from the North Sea

Anthropogenic climate change confronts marine organisms with rapid trends of concomitant warming and CO2 induced ocean acidification. The survival and distribution of species partly depend on their ability to exploit their physiological plasticity during acclimatization. Therefore, in laboratory studies the effects of simulated future ocean acidification on thermal tolerance, energy metabolism and acid–base regulation capacity of the North Sea population of the blue mussel Mytilus edulis were examined. Following one month of pre-acclimation to 10°C and control CO2 levels, mussels were exposed for two weeks to control and projected oceanic CO2 levels (390, 750 and 1120μatm) before being subjected to a stepwise warming protocol between 10°C and 31°C (+3°C each night). Oxygen consumption and heart rates, anaerobic metabolite levels and haemolymph acid–base status were determined at each temperature. CO2 exposure left oxygen consumption rate unchanged at acclimation temperature but caused a somewhat stronger increase during acute warming and thus mildly higher Q10-values than seen in controls. Interestingly, the thermally induced limitation of oxygen consumption rate set in earlier in normocapnic than in hypercapnic (1120μatm CO2) mussels (25.2°C vs. 28.8°C), likely due to an onset of metabolic depression in the control group following warming. However, the temperature induced increase in heart rate became limited above 25°C in both groups indicating an unchanged pejus temperature regardless of CO2 treatment. An upper critical temperature was reached above 28°C in both treatments indicated by the accumulation of anaerobic metabolites in the mantle tissue, paralleled by a strong increase in haemolymph PCO2 at 31°C. Ocean acidification caused a decrease in haemolymph pH. The extracellular acidosis remained largely uncompensated despite some bicarbonate accumulation. In all treatments animals developed a progressive warming-induced extracellular acidosis. A stronger pH drop at around 25°C was followed by stagnating heart rates. However, normocapnic mussels enhanced bicarbonate accumulation at the critical limit, a strategy no longer available to hypercapnic mussels. In conclusion, CO2 has small effects on the response patterns of mussels to warming, leaving thermal thresholds largely unaffected. High resilience of adult North Sea mussels to future ocean acidification indicates that sensitivity to thermal stress is more relevant in shaping the response to future climate change.

Complex sleep apnea syndrome in stroke patients

Fig. 1. A profile of Tiberius Claudius Germanicus appears on the obverse of this silver denarius struck during the Imperial Roman Era (ca. first century CE; photo provided courtesy of A Pangerl of www.romancoins.info). To the Editor We would like to thank Dr. Sacchetti and co-workers for their interest in our article [1]. Sacchetti et al. raise the question whether a stroke may transform, in selected patients, an obstructive sleep apnea syndrome (OSAHS) into a complex-sleep apnea syndrome (Comp-SAS) and postulate that the appearance of central respiratory events may represent a stable consequence of stroke, and may complicate the treatment approach to sleep apnea. This hypothesis is supported by their preliminary data showing mixed (obstructive and central) apneas four months after the stroke. This high prevalence of central and mixed respiratory events in stable phase after stroke is higher than that found in other studies, about the time course of sleep breathing disorders and central periodic breathing in stroke patients [2,3]. These data also contradict in part the attenuation of central respiratory events within week or a few months after the stroke described by the same authors or in OSAHS patients with CompSAS [4]. In OSAHS patients some predictive factors for appearance of CompSAS during CPAP treatment have been proposed [5], which include atrial fibrillation, use of opioids, sleep disruption and features of initial sleep apnea syndrome (in term of severity of obstructive apneas and presence of relevant mixed/central events). The last two factors are probably strictly related to the fluctuations of ventilatory control system and CO2 levels, that we documented in our paper [1], as well as, the fluctuations of arousal system in NREM sleep that have been described as possible distinctive patterns of some patients with OSAHS [6]. Finally, in our opinion, the question is to clarify if these or other factors can tell us whether initial ‘‘complex’’ cases of OSAHS are more prone to develop a clear CompSAS after a stroke and, whether as suggestedbySacchetti andco-workers, tomerge this ‘‘pre-stroke’’ profile of sleep disordered breathing with ‘‘post-stroke’’ features. Thismay enable us to findout possible factors able to distinguish patientswith a transient CompSAS frompatientswith a persistent one.

Soybean Leaf Gas‐Exchange Responses to Carbon Dioxide and Water Stress

AbstractAs global carbon dioxide concentrations rise, we need to understand the combination of direct effects of this gas and the anticipated effects of climate change, including drought, on physiology and growth of all crops. Effects of CO2 on plants begin at the leaf level; our objectives, therefore, were to determine interrelationships among factors governing gas exchange responses of soybean [Glycine max (L.) Merr.] leaves to elevated CO2 and water stress. Photosynthetic CO2 assimilation and transpiration rates were measured in cuvettes on leaflets of soybean (cv. Bragg) grown in controlled‐environment chambers at 330 and 660 μmol CO2 mol−1 air. Leaflets at high CO2, either water‐stressed or wellwatered, had higher photosynthetic and lower transpiration rates, and therefore higher water‐use efficiencies (WUE), than those at control CO2 levels. As irrigation was withheld during an ll‐d period, WUE decreased about 30 to 50% with respect to the well‐watered treatments. Midday leaf temperature and leaf‐to‐air vapor pressure gradient levels increased as the water stress progressed. For water stress treatments, midday leaf conductance (Gtw) was generally higher and residual internal conductance (Gr) was generally lower in low than in high CO2. Ratios of midday Gr/Gtc were nearly constant throughout the period in both the stressed and the well‐watered treatments. The ratios of intercellular Ci, to ambient Ca, CO2 concentration (i.e., Ci/Ca) during the water stress period remained similar to the respective nonstressed treatments within each CO2 level. These findings support the concept that leaf conductances are governed by CO2 assimilation rates under water‐stressed as well as unstressed conditions.

ROOT CO2 EFFECTS ON THE PEACH ROOT SYSTEM

Carbon dioxide is produced by microbial and plant respiration and accumulates in the soil. In previous field studies, CO2 levels were higher under a killed sod soil management system, relative to cultivation and herbicide systems (1.8 vs 0.8 and 1.0%), respectively. Our objective in these studies was to measure the effect of elevated levels of root system CO2 on root and shoot growth and nutrient uptake. Using soil and hydroponic systems in greenhouse studies, we maintained root system CO2 levels between 1.5 and 2.5%. Control CO2 levels were less than 1%. Root length density and dry matter partitioning to the root system were increased by root CO2 in soil and hydroponic studies; shoot growth was unaffected. In hydroponic culture, root CO2 increased P uptake, solution pH, root volume and the number of lateral roots/cm root axis. Elevated levels of CO2 in the root system stimulated root growth in both the soil and hydroponic studies.