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Background: in COVID-19 acute respiratory failure, the effects of CPAP and FiO2 on respiratory effort and lung stress are unclear. We hypothesize that, in the compliant lungs of early Sars-CoV-2 pneumonia, the application of positive pressure through Helmet-CPAP may not decrease respiratory effort, and rather worsen lung stress and oxygenation when compared to higher FiO2 delivered via oxygen masks. Methods: In this single-center (S.Luigi Gonzaga University-Hospital, Turin, Italy), randomized, crossover study, we included patients receiving Helmet-CPAP for early (< 48 h) COVID-19 pneumonia without additional cardiac or respiratory disease. Healthy subjects were included as controls. Participants were equipped with an esophageal catheter, a non-invasive cardiac output monitor, and an arterial catheter. The protocol consisted of a random sequence of non-rebreather mask (NRB), Helmet-CPAP (with variable positive pressure and FiO2) and Venturi mask (FiO2 0.5), each delivered for 20 min. Study outcomes were changes in respiratory effort (esophageal swing), total lung stress (dynamic + static transpulmonary pressure), gas-exchange and hemodynamics. Results: We enrolled 28 COVID-19 patients and 7 healthy controls. In all patients, respiratory effort increased from NRB to Helmet-CPAP (5.0 ± 3.7 vs 8.3 ± 3.9 cmH2O, p < 0.01). However, Helmet's pressure decreased by a comparable amount during inspiration (− 3.1 ± 1.0 cmH2O, p = 0.16), therefore dynamic stress remained stable (p = 0.97). Changes in static and total lung stress from NRB to Helmet-CPAP were overall not significant (p = 0.07 and p = 0.09, respectively), but showed high interpatient variability, ranging from − 4.5 to + 6.1 cmH2O, and from − 5.8 to + 5.7 cmH2O, respectively. All findings were confirmed in healthy subjects, except for an increase in dynamic stress (p < 0.01). PaO2 decreased from NRB to Helmet-CPAP with FiO2 0.5 (107 ± 55 vs 86 ± 30 mmHg, p < 0.01), irrespective of positive pressure levels (p = 0.64). Conversely, with Helmet's FiO2 0.9, PaO2 increased (p < 0.01), but oxygen delivery remained stable (p = 0.48) as cardiac output decreased (p = 0.02). When PaO2 fell below 60 mmHg with VM, respiratory effort increased proportionally (p < 0.01, r = 0.81). Conclusions: In early COVID-19 pneumonia, Helmet-CPAP increases respiratory effort without altering dynamic stress, while the effects upon static and total stress are variable, requiring individual assessment. Oxygen masks with higher FiO2 provide better oxygenation with lower respiratory effort. Trial registration Retrospectively registered (13-May-2021): clinicaltrials.gov (NCT04885517), https://clinicaltrials.gov/ct2/show/NCT04885517. [ABSTRACT FROM AUTHOR]

Recent climate extremes in Mongolia have ignited a renewed interest in understanding past climate variability over centennial and longer time scales across north-central Asia. Tree-ring width records have been extensively studied in Mongolia as proxies for climate reconstruction, however, the climate and environmental signals of tree-ring stable isotopes from this region need to be further explored. Here, we evaluated a 182-year record of tree-ring δ13C and δ18O from Siberian Pine (Pinus sibirica Du Tour) from a xeric site in central Mongolia (Khorgo Lava) to elucidate the environmental factors modulating these parameters. First, we analyzed the climate sensitivity of tree-ring δ13C and δ18O at Khorgo Lava for comparison with ring-width records, which have been instrumental in reconstructing hydroclimate in central Mongolia over two millennia. We also compared stable isotope records of trees with partial cambial dieback ('strip-bark morphology'), a feature of long-lived conifers growing on resource-limited sites, and trees with a full cambium ('whole-bark morphology'), to assess the inferred leaf-level physiological behavior of these trees. We found that interannual variability in tree-ring δ13C and δ18O reflected summer hydroclimatic variability, and captured recent, extreme drought conditions, thereby complementing ring-width records. The tree-ring δ18O records also had a spring temperature signal and thus expanded the window of climate information recorded by these trees. Over longer time scales, strip-bark trees had an increasing trend in ring-widths, δ13C (and intrinsic water-use efficiency, iWUE) and δ18O, relative to whole-bark trees. Our results suggest that increases in iWUE at this site might be related to a combination of leaf-level physiological responses to increasing atmospheric CO2, recent drought, and stem morphological changes. Our study underscores the potential of stable isotopes for broadening our understanding of past climate in north-central Asia. However, further studies are needed to understand how stem morphological changes might impact stable isotopic trends. [ABSTRACT FROM AUTHOR]

The evolution of hemoglobin function in the transition from water‐ to air‐breathing has been highly debated but remains unresolved. Here, we characterized the hemoglobin function in five closely related water‐ and air‐breathing catfishes. We identify distinct directions of hemoglobin evolution in the clades that evolved air‐breathing, and we show strong selection on hemoglobin function within the catfishes. These findings show that the lack of a general direction in hemoglobin function in the transition from water‐ to air‐breathing may have resulted from divergent selection on hemoglobin function in independent clades of air‐breathing fishes. Research highlights: 1.We show that the evolution of air‐breathing resulted in distinct changes in hemoglobin function.2.This illustrates that the adaptations to air‐breathing cannot be generalized across independent groups of air‐breathing fishes. [ABSTRACT FROM AUTHOR]

When measuring photosynthesis in mosses, the non-photosynthetic (brown) sections are usually removed and only the green sections are measured. However, how this pretreatment affects photosynthesis rates is unclear. Therefore, we studied the effect of removing the non-photosynthetic sections in three moss species with distinct morphological and stem-anatomical structures, comparing net CO2 assimilation rates (AN) of detached green and brown sections to those of intact shoots. Right after separation, the summed AN of the separated sections was significantly lower than those of the intact shoots for Pogonatum nudiusculum Mitt. and Pleuroziopsis ruthenica (Weinm.) Kindb. ex E. Britton, while no significant difference was found for Actinothuidium hookeri (Mitt.) Broth. However, AN recovered within a day, and the progressive reduction of AN expected if carbonsink removal was an important mechanism was not observed. Our study indicates that removal of non-photosynthetic sections results in an underestimation of the photosynthetic capacity of the green moss sections, but only for the species with relatively complex internal transport structures, and only immediately after the separation. The fast and transient response suggests a mechanism via an electrical signal induced by wounding or reduced hydraulic integrity, rather than through a reduced carbon-sink strength. More comprehensive investigations on signaling and other mechanisms regulating moss photosynthesis will contribute to more accurate measurement methods as well as a deeper understanding of moss ecophysiology and the contribution of mosses to carbon fluxes in terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

It is common practice to manipulate CO2 and O2 mole fraction during gas‐exchange experiments to suppress or exacerbate photorespiration, or simply carry out CO2 response curves. In doing so, it is implicitly assumed that metabolic pathways other than carboxylation and oxygenation are altered minimally. In the past few years, targeted metabolic analyses have shown that this assumption is incorrect, with changes in the tricarboxylic acid cycle, anaplerosis (phosphoenolpyruvate carboxylation), and nitrogen or sulphur assimilation. However, this problem has never been tackled systematically using non‐targeted analyses to embrace all possible affected metabolic pathways. Here, we exploited combined NMR, GC–MS, and LC–MS data and conducted non‐targeted analyses on sunflower leaves sampled at different O2/CO2 ratios in a gas exchange system. The statistical analysis of nearly 4,500 metabolic features not only confirms previous findings on anaplerosis or S assimilation, but also reveals significant changes in branched chain amino acids, phenylpropanoid metabolism, or adenosine turn‐over. Noteworthy, all of these pathways involve CO2 assimilation or liberation and thus affect net CO2 exchange. We conclude that manipulating CO2 and O2 mole fraction has a broad effect on metabolism, and this must be taken into account to better understand variations in carboxylation (anaplerotic fixation) or apparent day respiration. It is generally assumed that metabolic pathways other than carboxylation and oxygenation are altered minimally by changing CO2 and O2 conditions during gas exchange. Using isotope‐assisted metabolomics analyses, we show that manipulating CO2 and O2 has a broad effect on different major metabolic pathways, and this must be taken into to better interpret variations in carboxylation (anaplerotic fixation) or apparent day respiration. [ABSTRACT FROM AUTHOR]

Summary: It has been suggested that plant carbon (C) use by symbiotic arbuscular mycorrhizal fungi (AMF) may be compensated by higher photosynthetic rates because fungal metabolism creates a strong C sink that prevents photosynthate accumulation and downregulation of photosynthesis. This mechanism remains largely unexplored and lacks experimental evidence.We report here two experiments showing that the experimental manipulation of the mycorrhizal C sink significantly affected the photosynthetic rates of cucumber host plants. We expected that a sudden reduction in sink strength would cause a significant reduction in photosynthetic rates, at least temporarily.Excision of part of the extraradical mycorrhizal mycelium from roots, and causing no disturbance to the plant, induced a sustained (10–40%) decline in photosynthetic rates that lasted from 30 min to several hours in plants that were well‐nourished and hydrated, and in the absence of growth or photosynthesis promotion by mycorrhizal inoculation. This effect was though minor in plants growing at high (700 ppm) atmospheric CO2.This is the first direct experimental evidence for the C sink strength effects exerted by arbuscular mycorrhizal symbionts on plant photosynthesis. It encourages further experimentation on mycorrhizal source–sink relations, and may have strong implications in large‐scale assessments and modelling of plant photosynthesis. [ABSTRACT FROM AUTHOR]

Flowers are likely to be under various selective pressures not limited to reproduction and resource trade-offs. Here, we investigate the physiological responses (conductance, transpiration and respiration) of flowers under augmented temperature and supplemental watering, link these responses to actual flower longevity, and search for evidence of adaptive plasticity. Flower maintenance costs and plant fitness were investigated using the Andean geophyte, Rhodolirium montanum , in a manipulative field experiment. Maintenance determined by gas exchange was measured on fully expanded tepals; along with flower duration and its components, opening and closing. Fitness measured by fruit and seed production and seed set (mature/total) was examined. We artificially increased temperature and supplementally watered plants. Our study showed that flower longevity decreased under drier conditions, but the effect on flower opening and closing was even stronger, both of which advanced under higher temperatures without supplemental watering. Gas exchange also decreased, limiting water loss, under drier, warmer conditions. Those plants that reduced flower longevity under warming had higher total seed production and seed set. Plants that reduced conductance under warmed conditions also had higher seed set. These results suggest that plants are plastically optimizing fitness by reducing flower maintenance costs. Possible flower longevity and fitness connotations of our results under climate change are discussed. [ABSTRACT FROM AUTHOR]

Although grafting has become an effective tool to enhance many traits in horticultural crops, its role in improving the performance of local landraces is yet to be proven. The aim of this work was to assess the performance of the ‘Ramellet’ tomato, a landrace from the Balearic Islands, when grafted onto different rootstocks. For this purpose, two ‘Ramellet’ genotypes were grafted on two commercial (‘Beaufort’ and ‘Maxifort’) and a wild ( Solanum pimpinellifolium ) tomato rootstock species, and cultivated in greenhouse under commercial conditions. Plant yield, morphology and photosynthetic traits were measured in all combinations, with non-grafted and self-grafted ‘Ramellet’ plants used as controls. A significant effect of the rootstock on key parameters related to yield, plant growth and photosynthesis was found in both ‘Ramellet’ genotypes. Stomatal conductance increased, resulting in a decreased water-use efficiency in both genotypes grafted on the commercial rootstocks. Oppositely, when grafted on S. pimpinellifolium , stomatal conductance decreased and water-use efficiency increased in one of the ‘Ramellet’ genotypes. Remarkably, there was a significant correlation between water-use efficiency, plant growth and yield. Overall, the results highlight the potential of grafting to alter several physiological traits of local landraces and to provide new clues towards advancing our understanding in the underlying determinants of water-use efficiency and plant yield. [ABSTRACT FROM AUTHOR]

Leaf scald caused by Monographella albescens reduces the photosynthetic area, causing yield losses in rice. This study investigated the efficacy of the rhizobacteria Burkholderia pyrrocinia (BRM-32113) and Pseudomonas fluorescens (BRM-32111), combined with silicon (Si) fertilization, to reduce lesion size and the area under the disease progress curve (AUDPC), as well as to minimize the negative effects on gas exchange, chlorophyll a fluorescence, chlorophyll content and the activity of oxidative stress enzymes. The experiment used a completely randomized design with four replications and seven treatments. Compared with plants only fertilized with Si, plants fertilized with Si and treated with BRM-32113 showed reductions of 22% in scald lesion expansion and 37% in AUDPC, a 27% increase in the rate of CO2 assimilation ( A), a 33% decrease in the internal CO2 concentration ( Ci), and a 40% increase in ascorbate peroxidase activity. It was therefore concluded that the combination of BRM-32113 with Si fertilization reduces the severity of leaf scald, protecting the photosynthetic apparatus, thus representing a sustainable method of reducing the loss of income caused by leaf scald in rice. [ABSTRACT FROM AUTHOR]

The enzyme carbonic anhydrase (CA) has well-known functions in acid-base balance, respiratory gas exchange, and osmoregulation in teleost fishes. However, studies concerning the role of CA in elasmobranchs are still scarce. Therefore, the aim of this study is to present the current status of CA studies in sharks and rays, as well as to identify gaps and emerging needs, in order to guide future studies. This review is organized according to the main roles of CA, with further considerations on climate change and CA effects indicated as paramount, as strategies in the face of climate change can be crucial for species response. The literature review revealed a reduction in publications on CA over the years. In addition, a historical research differentiation is noted, where the first assessments on the subject addressed investigations on basic CA functions, while the most recent studies present a comparative approach among species as well as interdisciplinary discussions, such as ecology and phylogeny. Considering that several elasmobranchs are threatened, future studies should prioritize non-lethal methodologies, in addition to expanding studies to climate change effects on CA. [Display omitted] • Elasmobranch carbonic anhydrase studies have declined over the decades. • Osmoregulation is the most studied role involving Carbonic Anhydrase. • Most elasmobranchs did have not yet been assessed regarding carbonic anhydrase. • Environmental alterations, such as climate change and pollution affect this enzyme. [ABSTRACT FROM AUTHOR]

Low levels of crassulacean acid metabolism (CAM) are demonstrated in two species with C 4 photosynthesis, Portulaca cyclophylla and P. digyna. The expression of CAM in P. cyclophylla and P. digyna is facultative, i.e. optional. Well-watered plants did not accumulate acid at night and exhibited gas-exchange patterns consistent with C 4 photosynthesis. CAM-type nocturnal acidification was reversible in that it was induced following drought and lost when droughted plants were rewatered. In P. cyclophylla , droughting was accompanied by a small but discernible net uptake of CO 2 during the dark, whereas in P. digyna , net CO 2 exchange at night approached the CO 2 compensation point but did not transition beyond it. This report brings the number of known C 4 species with a capacity for expressing CAM to six. All are species of Portulaca . The observation of CAM in P. cyclophylla and P. digyna is the first for species in the opposite-leaved (OL) Portulacelloid-anatomy lineage of Portulaca and for the Australian clade therein. The other four species are within the alternate-leaved (AL) lineage, in the Atriploid-anatomy Oleracea and the Pilosoid-anatomy Pilosa clades. Studies of the evolutionary origins of C 4 and CAM in Portulaca will benefit from a more wide-range survey of CAM across its species, particularly in the C 3 -C 4 intermediate-containing Cryptopetala clade. [ABSTRACT FROM AUTHOR]

Background: Mitochondrial respiration in the dark (Rdark) is a critical plant physiological process, and hence a reliable, efficient and high-throughput method of measuring variation in rates of Rdark is essential for agronomic and ecological studies. However, currently methods used to measure Rdark in plant tissues are typically low throughput. We assessed a high-throughput automated fluorophore system of detecting multiple O2 consumption rates. The fluorophore technique was compared with O2-electrodes, infrared gas analysers (IRGA), and membrane inlet mass spectrometry, to determine accuracy and speed of detecting respiratory fluxes. Results: The high-throughput fluorophore system provided stable measurements of Rdark in detached leaf and root tissues over many hours. High-throughput potential was evident in that the fluorophore system was 10 to 26-fold faster per sample measurement than other conventional methods. The versatility of the technique was evident in its enabling: (1) rapid screening of Rdark in 138 genotypes of wheat; and, (2) quantification of rarely-assessed whole-plant Rdark through dissection and simultaneous measurements of above- and below-ground organs. Discussion: Variation in absolute Rdark was observed between techniques, likely due to variation in sample conditions (i.e. liquid vs. gas-phase, open vs. closed systems), indicating that comparisons between studies using different measuring apparatus may not be feasible. However, the high-throughput protocol we present provided similar values of Rdark to the most commonly used IRGA instrument currently employed by plant scientists. Together with the greater than tenfold increase in sample processing speed, we conclude that the high-throughput protocol enables reliable, stable and reproducible measurements of Rdark on multiple samples simultaneously, irrespective of plant or tissue type. [ABSTRACT FROM AUTHOR]

The purpose of this study is to analyze natural and anthropogenic forest ecosystems in order to establish the functional tools for ecophysiological characterization and monitoring of the investigated sites. Related to leaf traits, the parameters of foliar gas-exchange, specific leaf area (SLA), leaf dry matter content (LDMC) and carbohydrates fractions were analyzed. Four sites (riverside coppices) represented by natural forests and forestry plantations were studied and, a control area the zone with integral protection (Letea Forest, Hăşmacu Mare) was considered; all are located along the Chilia branch from Danube Delta Biosphere Reserve. In plantations, in representative species, the metabolic loss was increased by an enhanced of respiration and transpiration processes, higher than in natural forest ecosystems. Statistical analysis has found significant differences in instant water use efficiency, respiration and leaf dry matter content in species from plantations in comparison with natural forest but not so significant among natural forest and natural reserve (Letea Forest-Hăşmacu Mare) at the p <0.05, level of significance. Furthermore, the native species (Populus alba L., Salix alba L.) had a low specific leaf area (SLA) and a high leaf dry matter content (LDMC) in conditions of habitats of natural/ quasi-natural condition with a lower (semi-controlled) anthropogenic intervention and a high SLA and low LDMC in native species and hybrids poplar at cultivated plantation. The results of this study indicate that representative species are responsive to the habitat conditions indicating the disturbance of the sites and indirectly, the anthropogenic pressure. [ABSTRACT FROM AUTHOR]

Oilseed rape (Brassica napus L.) yield is strongly decreased by water deficit, and crop-management solutions are urgently required considering the emerging difficulties in breeding for drought-tolerant varieties. Film-forming antitranspirants (polymers) are agrochemicals that, applied to the crop canopy, mechanically block the stomata and decrease canopy transpiration. In this study, the drought-protection efficacy of an adaxial-surface application at the flowering stage of two film-forming treatments (poly-1-p-menthene and di-1-p-menthene) was investigated in pot-grown, droughted oilseed rape over two glasshouse experiments. Over the drought period, the two compounds reduced leaf stomatal conductance (P < 0.001), and as the soil moisture deficit increased, they sustained carbon assimilation and improved water-use efficiency with differing efficacy. Following the antitranspirant treatments, ABA concentration in leaves and reproductive organs was severely reduced and this was accompanied by significant improvements in leaf and flower-pod water potential. Drought significantly decreased the seed dry matter production of oilseed rape plants, by 39% on average. The treatments significantly increased seed dry matter by13%(poly-1-p-menthene) and17%(di-1-p-menthene), on average, compared with the unsprayed droughted plants, as a result of a significant increase in number of pods per plant, by 11% and 13%, respectively. The results suggest that film-forming compounds may be a useful crop-management tool to avoid severe drought-induced yield losses in oilseed rape by improving water-use efficiency and plant water status, thus alleviating ABA signalling under water deficit. [ABSTRACT FROM AUTHOR]

Viticulture is in great need of new rootstocks sharing features of scion growth control and tolerance to major biotic and abiotic stress factors. A two year study was carried out in pots to assess performances of the two new M1 and M3 rootstocks vs. those of the commercial rootstocks 1103P and 101-14. Potted vines of M1, M3, 1103P and 101-14 rootstocks were grown in a calcareous and non calcareous soil and for two consecutive seasons subjected to three N supply levels at 0, 2 and 4 g of N per pot. Vegetative growth, leaf gas exchange, leaf greenness index (GI) and leaf blade nutrition were assessed. M1 and 1103P were the least vigorous genotypes in terms of total pruning weight; M1 also manifested a stronger apical dominance. Both M rootstocks and 101-14 showed increased leaf WUE at both N supply levels which was due to ability to maintain, at increasing N supply, similar leaf assimilation rates while significantly reducing leaf transpiration. Common tendency of any rootstocks was that increasing N supply corresponded to lowered leaf concentration of K, P, Mg and B. M1 was able to combine a series of desirable features including lower vigor, strong apical dominance, higher WUE at increasing N supply and quite well balanced leaf nutritional pattern. In the present trial M3 did not have the expected devigorating effect. [ABSTRACT FROM AUTHOR]

Heterosis is one of the greatest practical achievements of plant breeding and has been extensively used in crop improvement in maize. However, the physiological basis of heterosis still remains poorly understood despite its manifestation at early stages of the plant life cycle. Therefore, a better understanding of the physiological mechanisms associated with heterosis may enable further exploitation of this phenomenon. Five maize hybrids and their parental lines were grown in a greenhouse under two water regimes (well watered and water stressed). Plant growth, different root traits, plant water use and water use efficiency and gas-exchange and chlorophyll fluorescence, nitrogen content and stable oxygen, carbon and nitrogen composition and stomatal density of leaves were measured. Plant height, shoot biomass and leaf area were higher in hybrids than in their respective parents in both control and stress conditions. Moreover, hybrids showed a better water use and water use efficiency for biomass than inbred lines. Significant heterosis was also found for photosynthetic rate, stomatal conductance, transpiration rate and the C i / C a ratio under water stress conditions, whereas for control conditions the differences were not significant. Likewise, root weight density and root length density were higher in hybrids than parents, especially underwater stress. No heterosis occurred for stable isotope composition under either water regime. The results do not support a constitutively better water status as a cause of heterosis under well watered conditions. [ABSTRACT FROM AUTHOR]

Establishing rates of injury to plants and the physiological impact of this injury provides essential data in the development of economic injury levels, but variation of sex effects is not often considered. Here, we examined injury by the Colorado potato beetle, Leptinotarsa decemlineata ( Say) ( Coleoptera: Chrysomelidae), larvae and adult males and females on potato, Solanum tuberosum L. ( Solanaceae). Specifically, we looked for adult sex differences between males and females in injury rates (= leaf consumption rates), and examined the impact of all types of injury (larval, adult male, and adult female) on gas exchange parameters of remaining potato leaf tissue. Experiments were conducted in the field and in growth chambers on Frito-Lay proprietary and Pike chipping-potato varieties at pre-blooming and blooming stages. We found no change in photosynthetic rates on remaining (uninjured) leaf tissue infested with male, female, or fourth-stage larva of Colorado potato beetle. However, when the midrib was cut in trials with male beetles, the remaining tissue above the injury exhibited photosynthetic rate reductions as a result of stomatal limitations. These findings are consistent with the pattern that we and other researchers have observed with gross tissue removal by various insects on other plant species. Adult females consumed more tissue than males, and temperature was positively correlated with feeding rates for both sexes. Sex-related differences in feeding rate are most important to studies quantifying consumption rates for economically important species because of its potential impact on resulting economic injury level calculations. [ABSTRACT FROM AUTHOR]

Background and Aims: Hepatopulmonary syndrome (HPS) affects 10-32 % of patients with cirrhosis and is defined by liver abnormalities, intrapulmonary vascular dilatations (IPVDs), and abnormal oxygenation. However, published criteria for abnormal oxygenation are inconsistent. We sought to evaluate variation in oxygenation over time and to compare various diagnostic criteria for validity, based on their diagnostic stability over time and ability to identify patients with clinically relevant findings. Methods: We retrospectively analyzed oxygenation and diffusion capacity in patients with liver abnormalities and IPVDs who had ≥2 arterial blood gases (ABGs) at the University of Toronto or Universite de Montreal. We compared the performance of nine possible oxygenation criteria for HPS and for each explored whether validity improved when requiring two consecutive abnormal ABGs on different days. Results: Mean PaO was 68.4 mmHg and annual within-patient coefficient of variation 6.3 % (58 patients). Applying published criteria, 8.6-15.5 % of patients initially diagnosed with HPS no longer met the criterion for HPS on a subsequent ABG (re-classified). Requiring two consecutive abnormal ABGs on different days: (1) reduced the proportion of re-classified patients (9/9 criteria); (2) identified patients with more rapid progression in hypoxemia and greater difference in rate of progression between HPS and non-HPS (7/9 criteria); and (3) identified patients with lower diffusion and a larger difference in diffusion between HPS and non-HPS (8/9 criteria). Conclusions: Oxygenation is variable in this population, and requiring two abnormal results might reduce misdiagnosis and better differentiate patients with and without HPS according to clinically relevant markers of disease. [ABSTRACT FROM AUTHOR]

In the present paper a series of WUE expressions, including the physiological and agronomical, were compared in potted cv. Sangiovese ( Vitis vinifera L.) grapevines which were either well watered (WW) or subjected to progressive post-veraison water stress (WS) by supplying decreasing fractions (i.e. 70%, 50% and 30%) of daily canopy transpiration ( T c ) concurrently recorded via a plant-enclosure gas exchange system. While single-leaf intrinsic water-use efficiency (WUE i ) increased with water stress severity, seasonal whole-canopy WUE were similar at pre-stress, 70% T c , and upon rewatering but dropped during severe water stress. WUE calculated as mass of dry weight stored in annual biomass (leaves, canes and clusters) per liter of water used, did not differ on a seasonal basis, whereas WW and WS showed similar grape composition despite the latter suffered a 25% yield reduction. Results confirm that whole-canopy WUE is a much better index than single-leaf based WUE parameter for extrapolation to agronomic WUE and actual grape composition. Under our specific case study, due to high reactivity of Sangiovese to early yellowing and shedding of basal leaves, it can be recommended that post-veraison water supply to Sangiovese vines should not be lower than 70% of daily vine water use. [ABSTRACT FROM AUTHOR]

Understanding how water use efficiency (WUE) changes under drought is crucial for interpreting adaptive responses of species and cultivars to such abiotic stress. Several recent papers have concluded that in grapevine these responses and the guidelines stemming therefrom can differ, depending upon the parameter chosen to express WUE. In the present paper a complete set of WUE expressions, including the physiological and agronomical, were compared in potted, fruiting cv. Montepulciano ( Vitis vinifera L.) grapevines which were either well watered (WW) or subjected to progressive pre-veraison drought (WS) by supplying decreasing fractions (i.e. 70%, 50% and 30% of daily vine transpiration, T g ) determined gravimetrically before vines were fully rewatered. While single-leaf intrinsic water-use efficiency (WUE i ) increased with water stress severity, seasonal and diurnal whole-canopy WUE were similar at pre-stress, 70% T g , and upon rewatering but dropped in WS during severe water stress. Agronomic WUE calculated as mass of dry weight stored in annual biomass (leaves, canes and bunches) per L of water used, was also lower in WS, whereas WS had similar must composition with WW despite a 37% reduction in the yield per vine. Results warn that whole-canopy WUE is a much better index than any single-leaf based WUE parameter for extrapolation to agronomic WUE and actual grape composition. Under our specific case study, it can be recommended that, to avoid significant profit loss, water supply to drought stressed Montepulciano at pre-veraison should not be lower than 70% of daily vine water use. [ABSTRACT FROM AUTHOR]

Free-piston engine generator (FPEG) contains two gasoline engines and a linear generator, which has attracted considerable research interest for its potential application to electricity generation. The device has low mechanical loss and variable compression ratio which means energy conservation and multiple fuel adaptability. Previous studies have found that the scavenging process was vital to the stable operation of the FPEG system. In order to know the features, an experiment was carried out to analysis the scavenging process of FPEG. In the experiment, both the pressure in cylinder and in scavenge box were tested. Experiment results showed that: the combustion process of FPEG variated cycle to cycle at low speed operation condition for the instability of scavenging process, while in traditional mode the engine performed very well. Computational fluid dynamics (CFD) model designed according to prototype was introduced to analysis the difference between FPEG and traditional two-stroke engine in scavenging process. Calculation results showed that: the relative low scavenging box volume variation rate of FPEG was the effective factor on the scavenging efficiency, which led to low-speed instability. And the difference of scavenging structure between FPEG and traditional engine was responsible for it. In order to optimize the scavenging system, operation parameters including diameter of piston assembly, volume of scavenging box and charging pressure were investigated. Results showed that: the low proportion of piston assembly diameter on bore and high inlet pressure effectively improved the scavenging efficiency. Especially, when the proportion of piston assembly diameter on bore was less than 0.4, the difference of scavenging efficiency of FPEG and traditional engine was less than 6%. [ABSTRACT FROM AUTHOR]

Highlights: [•] We compared C3- and C4-type cover crops for use in vineyard situations. [•] The study was conducted in the field in Germany and in pots in Argentina. [•] We quantified water consumption/loss and CO2 uptake/efflux. [•] Measurements were conducted with whole plant chambers. [•] C4 plants had slightly improved water use efficiencies. [ABSTRACT FROM AUTHOR]

Canada's northern boreal forests are undergoing rapid change associated with warming trends, with permafrost thaw leading to increased forest stress and compositional changes in plant communities. Within this context, the influence of commonly occurring, resident natural enemies on plant species remains poorly understood. One of the dominant deciduous shrub genera, Betula, is abundant in northern forest-wetland landscapes, and is highly susceptible to leaf galling by mites, but the impacts of these specialist arthropod herbivores on plant-level physiology remain unknown., We examined the impacts of mite galling on a suite of ecophysiological traits in Betula glandulosa, a shrubby species commonly found on permafrost plateaus, bogs and fens in a boreal wetland-forest mosaic, and on two congeners, B. occidentalis and B. neoalaskana, found only on plateaus., B. glandulosa leaves on plateaus showed marked declines in photosynthetic capacity [ A max], stomatal conductance [ gs], and transpiration [ E] in response to galling. However, B. glandulosa leaves in bogs and fens did not respond similarly, implying strong habitat-related differences in response to galling herbivory. The impacts on plateaus were reinforced by similar responses of B. occidentalis and B. neoalaskana leaves to galling, and confirmed that on plateaus, galling appears to have significant negative effects on photosynthetic uptake. Moreover, carbon uptake in infested leaves showed photosynthetic declines even at low galling intensity. Interestingly, neighbouring nongalled leaves adjacent to galled ones showed similar declines in gas-exchange rates in all the three species found on plateaus. However, reduced stomatal conductance and transpiration in galled and neighbour leaves did not affect whole plant water status, as we found no differences in either midday or diurnal stem water potentials between galled and gall-free stems in any of the species., Synthesis: Based on these findings, we suggest that the impacts of mite galling are variable, and are likely to be most pronounced in habitats and on individuals that are already exposed to abiotic stresses such as the cooler, but more variable soil temperatures experienced by individuals on permafrost plateaus. Furthermore, galling can potentially contribute to localized thaw processes in these environments via impacts on plant functioning. [ABSTRACT FROM AUTHOR]

Mature forest canopies sustain an enormous diversity of herbivorous arthropods; however, with the exception of species that exhibit large-scale outbreaks, canopy arthropods are thought to have relatively little influence on overall forest productivity. Diminutive gall-inducing mites (Acari; Eriophyoidae) are ubiquitous in forest canopies and are almost always highly host specific, but despite their pervasive occurrence, the impacts of these obligate parasites on canopy physiology have not been examined. We have documented large declines in photosynthetic capacity (approx. 60%) and stomatal conductance (approx. 50%) in canopy leaves of mature sugar maple ( Acer saccharum) trees frequently galled by the maple spindle gall mite Vasates aceriscrumena. Remarkably, such large impacts occurred at very low levels of galling, with the presence of only a few galls (occupying approx. 1% of leaf area) compromising gas-exchange across the entire leaf. In contrast to these extreme impacts on the leaves of adult trees, galls had no detectible effect on the gas-exchange of maple saplings, implying large ontogenetic differences in host tolerance to mite galling. We also found a significant negative correlation between canopy tree radial increment growth and levels of mite galling. Increased galling levels and higher physiological susceptibility in older canopy trees thus suggest that gall-inducing mites may be major drivers of 'age-dependent' reductions in the physiological performance and growth of older trees. [ABSTRACT FROM AUTHOR]

Abstract: The effects of two types of hydrophilic polymers on drought and salt resistance of 1-year-old cuttings of Populus popularis 35–44 were investigated in this study. The polymers used in the experiments were Stockosorb 500 XL (Stockosorb) (a granular type, cross-linked poly potassium-co-(acrylic resin polymer)-co-polyacrylamide hydrogel) and Luquasorb® product (a powder type of potassium polyacrylate), which were manufactured by Stockhausen GmbH Krefeld and BASF Corporation in Germany, respectively. Drought or salt stress significantly decreased leaf photosynthesis and transpiration, as well as plant water-consumption and dry weight. A significant reduction occurred in Drought+NaCl-stressed plants. Soils treated by 0.5% Stockosorb or Luquasorb markedly alleviated the inhibition of plant growth and leaf gas-exchange that were caused by drought and/or salt stress treatments, and the occurrence of stress-induced leaf injury was delayed for 31 and 51 days, respectively. Experimental results showed that hydrophilic polymers in root media assisted P. popularis plants to tolerate the drought and salt stresses, due to the following reasons: (1) roots took up the retained water from hydrophilic polymers when water was deficient in the soil (Stockosorb-treated plants exhibited a higher rate of water uptake); (2) under saline conditions, Stockosorb and Luquasorb held Na+ and Cl− in the soil solution due to their high water-holding capacity, thus limiting an excessive accumulation of toxic ions in the plant organs; furthermore, the exchangeable K+ that contained in Stockosorb and Luquasorb resulted in an improved K+/Na+ homeostasis in salinized plants; (3) hydrophilic polymers aided the plants to tolerate an interactive impacts of drought and salt stresses, which was mainly accounted for their water- and salt-holding capacities. In comparison, the growth and survival enhancement effects of the hydrophilic polymers on Drought+NaCl-treated plants was more evident by Luquasorb application, because it supplied water to plants at a lower rate during soil drying, thus prolonging the duration of water supply and allowed roots to grow in an environment of lower salinity for a long period of salt and drought stresses. [Copyright &y& Elsevier]

Abstract: The effect of N availability on photosynthetic capacity, growth parameters and yield was studied in field-grown durum-wheat plants at both the leaf and canopy levels. Two contrasting nitrogen levels (120 and 0kgha−1) were assayed in a randomised block design with nine replicates each. Total biomass was measured at anthesis and yield and its agronomical components at maturity. Photosynthetic measurements were performed 2 weeks after anthesis in two plots of each N treatment. Flag leaves were measured, using a LI-COR 6400 combined with the chlorophyll fluorescence meter, and the whole canopy by measuring CO2 and H2O fluxes in an innovative canopy-chamber system. We showed a clear increase in photosynthetic gas exchange and chlorophyll contents with N fertilisation at both canopy and leaf levels. As a consequence the increase in yield as response to N fertilisation seems the result of a larger green leaf area combined with a higher photosynthetic capacity of the leaves attributable to an increase in the maximum carboxylation velocity of Rubisco. Moreover gas-exchange measurements of the flag leaf during grain filling seem to provide a realistic characterisation, not just of the photosynthetic performance of the crop, but also about the impact of N availability on yield. Thus, measurements performed on the flag leaf matched those at the canopy level, with proportional increases in terms of gas exchange and chlorophyll content, providing a fast, cheap and reliable estimation of canopy photosynthesis and the grain yield attained by the crop. [Copyright &y& Elsevier]

Abstract: Prone position may delay the development of ventilator-induced lung injury (VILI), but the mechanisms require better elucidation. In experimental mild acute lung injury (ALI), arterial oxygen partial pressure (), lung mechanics and histology, inflammatory markers [interleukin (IL)-6 and IL-1β], and type III procollagen (PCIII) mRNA expressions were analysed in supine and prone position. Wistar rats were randomly divided into two groups. In controls, saline was intraperitoneally injected while ALI was induced by paraquat. After 24-h, the animals were mechanically ventilated for 1-h in supine or prone positions. In ALI, prone position led to a better blood flow/tissue ratio both in ventral and dorsal regions and was associated with a more homogeneous distribution of alveolar aeration/tissue ratio reducing lung static elastance and viscoelastic pressure, and increasing end-expiratory lung volume and . PCIII expression was higher in the ventral than dorsal region in supine position, with no regional changes in inflammatory markers. In conclusion, prone position may protect the lungs against VILI, thus reducing pulmonary stress and strain. [Copyright &y& Elsevier]

Abstract: A stand-scale forest model has been developed that dynamically simulates, besides carbon (C) and water (H2O) fluxes, wood tissue development from physiological principles. The forest stand is described as consisting of trees of different size cohorts (for example, dominant, co-dominant and suppressed trees), either of the same or of different species (deciduous or coniferous). Half-hourly C and H2O fluxes are modeled at the leaf, tree and stand level. In addition to total growth and yield, the model simulates the daily evolution of tracheid or vessel biomass and radius, parenchyma and branch development. From these data early and latewood biomass, wood tissue composition and density are calculated. Simulation of the labile C stored in the living tissues allows for simulation of trans-seasonal and trans-yearly effects, and improved simulations of long-term effects of environmental stresses on growth. A sensitivity analysis was performed to indicate the main parameters influencing simulated stem growth and wood quality at the tree and stand level. Case studies were performed for a temperate pine forest to illustrate the main model functioning and, more in particular, the simulation of the wood quality. The results indicate that the ANAFORE model is a useful tool for simultaneous analyses of wood quality development and forest ecosystem functioning. [Copyright &y& Elsevier]

Abstract: During an almost three months long expedition in the Arctic Ocean, the Beringia 2005, dissolved gaseous mercury (DGM) was measured continuously in the surface water. The DGM concentration was measured using an equilibrium system, i.e. the DGM in the water phase equilibrated with a stream of gas and the gas was thereafter analysed with respect to its mercury content. The DGM concentrations were calculated using the following equation, DGM = Hgeq / k H'' where Hgeq is the equilibrated concentration of elemental mercury in the gas phase and k H'' is the dimensionless Henry''s law constant at desired temperature and salinity. During the expedition several features were observed. For example, enhanced DGM concentration was measured underneath the ice which may indicate that the sea ice acted as a barrier for evasion of mercury from the Arctic Ocean to the atmosphere. Furthermore, elevated DGM concentrations were observed in water that might have originated from river discharge. The gas-exchange of mercury between the ocean and the atmosphere was calculated in the open water and both deposition and evasion were observed. The measurements showed significantly enhanced DGM concentrations, compared to more southern latitudes. [Copyright &y& Elsevier]

We examined the tradeoffs between stand-level water use and carbon uptake that result when biomass production of trees in plantations is maximized by removing nutrient and water limitations. A Populus trichocarpa Torr. x P. deltoides Bartr. & Marsh. plantation was irrigated and received frequent additions of nutrients to optimize biomass production. Sap flux density was measured continuously over four of the six growing-season months, supplemented with periodic measurements of leaf gas exchange and water potential. Measurements of tree diameter and height were used to estimate leaf area and biomass production based on allometric relationships. Sap flux was converted to canopy conductance and analyzed with an empirical model to isolate the effects of water limitation. Actual and soil-water-unlimited potential CO2 uptakes were estimated with a canopy conductance constrained carbon assimilation (4C-A) scheme, which couples actual or potential canopy conductance with vertical gradients of light distribution, leaf-level conductance, maximum Rubisco capacity and maximum electron transport. Net primary production (NPP) was about 43% of gross primary production (GPP); when estimated for individual trees, this ratio was independent of tree size. Based on the NPP/GPP ratio, we found that current irrigation reduced growth by about 18% compared with growth with no water limitation. To achieve maximum growth, however, would require 70% more water for transpiration, and would reduce water-use efficiency by 27%, from 1.57 to 1.15 g stem wood C kg-1 water. Given the economic and social values of water, plantation managers appear to have optimized water use. [ABSTRACT FROM AUTHOR]

Abstract: Dissolved noble gases and tritium were analyzed at a series of high-intensity methane gas seeps in the Black Sea to study the transport and gas exchange induced by bubble-streams in the water column. These processes affect marine methane emissions to the atmosphere and are therefore relevant to climate warming. The seep areas investigated are located in the Dnepr paleo-delta, west of Crimea, and in the Sorokin Trough mud volcano area, south-east of Crimea. Noble gas concentration profiles at active seep sites revealed prominent anomalies compared to reference profiles that are unaffected by outgassing. Supersaturations of the light noble gases helium and neon observed relatively close to the sea floor are interpreted as effects of gas exchange between the water and the rising bubbles. Depletions of the heavy noble gases argon, krypton and xenon that were detected above an active, bubble-releasing mud volcano appear to be related to the injection of fluids depleted in noble gases that undergo vertical transport in the water column due to small density differences. In both cases, the noble gas anomalies clearly document seep-specific processes which are difficult to detect by other methods. Helium is generally enriched in the deep water of the Black Sea due to terrigenic input. Although exceptionally high helium concentrations observed in one seep area indicate a locally elevated helium flux, most of the seeps studied seem to be negligible sources of terrigenic helium. Noble gas analyses of sediment pore waters from the vicinity of a mud volcano showed large vertical gradients in helium concentrations. The helium isotope signature of the pore waters points to a crustal origin for helium, whereas the deep water of the Black Sea also contains a small mantle-type component. [Copyright &y& Elsevier]

Abstract: This study investigated the seasonal modification of wax deposition, and the impact of epicuticular wax on gas-exchange as well as photoinhibition in Leucadendron lanigerum, a species from the Proteaceae family with wax-covered leaf surfaces and the stomata also partially occluded by wax. The results of this study demonstrated that the deposition of epicuticular wax in L. lanigerum is dependent on the age of the leaf as well as the season, and generation and regeneration of wax occur mostly in spring while transformation and also degeneration of wax crystals occur in winter. Epicuticular waxes decreased cuticular water loss, but had little impact on leaf reflectance. The temperature of leaves without wax was lower than that of wax-covered leaves, indicating that the rate of transpiration impacted more on leaf temperature than reflectance of light in the PAR range in L. lanigerum. The wax coverage at the entrance of stomata in L. lanigerum increased resistance to gas diffusion and as a consequence decreased stomatal conductance, transpiration and photosynthesis. Also, the results indicated that epicuticular waxes do help prevent photodamage in L. lanigerum, and so this property could benefit plants living in arid environments with high solar radiation. [Copyright &y& Elsevier]

To follow the early response of the photosynthetic apparatus to elevated [CO2] applied in combination with other stress factors we exposed 19-day-old bean plants (Phaseolus vulgaris L. cv. Cheren Starozagorski) for relatively short period (4 days, 8h per day) to different temperature, light and [CO2] regimes: 23 or 39°C air temperature, low (100 μmol m-2s-1 – LL) or high (1000 μmol m-2s-1 – HL) photosynthetic photon flux density (PPFD) and ambient (350 μmol mol-1) or elevated (1300 μmol mol-1) CO2 concentration. Chlorophyll fluorescence kinetics and the response of assimilation rate to intercellular CO2 concentration were registered during the 4-day period. At growth temperature (23°C), we observed some stimulation of photosynthesis by elevated [CO2], expressed by higher maximal net photosynthetic rate, carboxylation capacity and electron transport capacity, while at high temperature (39°C) the effect of elevated [CO2] on photosynthesis was negative, i.e. HT induced downward acclimation. The negative effect of the CO2 enrichment at HT, expressed as diminished Rubisco activity and limitations in RuBP and P regeneration, may be due to starch accumulation as it was seen from the electron micrographs. Our results show that the ratio of intercellular to ambient [CO2], which reflects the coupling between stomata and photosynthetic CO2 assimilation, was unaffected by elevated [CO2] as well as by changes in light and temperature. In the 4-day period, the PSII efficiency was not affected by the elevated [CO2]. The fluorescence parameters were noticeably reduced at HL already on the first day and decreased further with time. We concluded that 4-day growth of plants in atmosphere with CO2 concentration more than three times above the natural modifies the response of plants to light and temperature, which was connected with functional and structural changes. [Copyright &y& Elsevier]

In order to understand the physiology and ecology of perennial shrub species occupying the banks of ephemeral streams we studied the plant water relations and gas-exchange characteristics of six perennial shrub species growing along an ephemeral stream (arroyo) in the northern Chihuahuan Desert. Two of the species are restricted to riparian habitats (Brickellia laciniata and Chilopsis linearis), three are classified as semi-riparian (Fallugia paradoxa, Prosopis glandulosa, and Rhus microphylla) and one is considered to be non-riparian (Flourensia cernua). Differences in gas-exchange patterns and water relations emerged among these six species, yet differences among obligate, semi-riparian, and non-riparian classes of species were evident, but not universal. Chilopsis and Brickellia did not develop the low plant water potentials that characterized some semi-riparian (Rhus) and non-riparian species (Flourensia) during periods of drought. Rates of photosynthesis and transpiration were highest in Prosopis throughout the study, and were relatively constant in Chilopsis during and after drought. Whether water became available as channel flow or direct rainfall appeared to play a role in the physiology of these arroyo shrubs. [Copyright &y& Elsevier]

As potassium (K) requirement of grapevine (Vitis vinifera L.) berries is high and phloem translocation from mature leaves to developing organs is well established, it was posited that shoot trimming, a widely applied technique which alters the source-sink balance and the mature-to-immature foliage ratio of a canopy, may influence K deficiency. Six-year-old Cabernet Sauvignon grapevines were grown in 0.045 m3 pots (one plant per pot) filled with a soil sampled from a vineyard previously displaying K deficiency symptoms. Two levels of K supply (K0, no K added; K1, 25 g K per pot added in five splits from bloom to post veraison) were tested on vines that for each level were left (a) untrimmed and trimmed at ten main leaves with (b) or without (c) maintenance of lateral shoots in a split-plot design. Potassium concentration of leaf blades, berries and canes, vegetative growth and leaf gas exchange were recorded throughout the season; yield, grape quality and must characteristics were determined at fruit maturity. While adding potassium to the soil resulted in higher K concentration in blades of both main and lateral shoots and berries at harvest, trimming with removal of lateral shoots resulted in lower blade K concentration of the main leaves at harvest and more severe K deficiency symptoms regardless of K soil availability. Berry K concentration and the fraction of whole-plant K partitioned to clusters were not significantly affected by trimming. Gas-exchange, vegetative growth, yield and grape quality were not affected by the seasonal K fertilization, whereas the latter was impaired when trimming with excision of lateral shoots was applied. The results indicate that if shoot trimming is not followed by an adequate regrowth of secondary shoots an excessive depletion of potassium from the retained old basal leaves occurs during fruit maturity and increases the risk of leaf K deficiency, particularly in the K0 treatment. [ABSTRACT FROM AUTHOR]

An automated transient-state closed-system canopy-chamber for gas-exchange determinations of field-crops was developed to allow unattended day and night, high frequency CO2 and H2O exchange measurements, with short measurement time (15 s) and high scanning rate (0.5 s). Environment tests on the chamber performance indicated that: atmospheric pressure variation during operation was 10–20 Pa and limited to a few seconds; leaks introduced maximum errors of 1% in the flux calculation; turbulence effect on CO2 and H2O fluxes was not detectable; during the measurement period, temperature build-up inside the chamber was typically within 1–2 °C range; photosynthetic photon flux density (Rp) attenuation by the chamber as a whole was in the 15–20% range; whereas, net radiation (Rn) inside the chamber was always higher than outside by 10–20%. The flux determinations of the automated canopy-chamber were compared with other methods. Daily evapotranspiration (E) of artichoke obtained by canopy-chamber was at the most 4.2% lower than E obtained by high-precision weighing lysimeter. Diurnal E and carbon exchange rates (A) of sugarbeet and marjoram crops obtained by canopy-chamber closely followed the pattern of those obtained by the Bowen-ratio/energy-balance (BREB) method, with maximum daily underestimations of 6–8 and 5–6% for E and A, respectively. No differences in flux calculations came out when the rate of change in CO2 and H2O concentrations was derived either by linear or quadratic regressions (QR). The results of all tests and comparisons showed that the automated chamber presented is a valuable and accurate tool for monitoring day and night CO2 and H2O fluxes. [Copyright &y& Elsevier]

Background: The majority of patients with severe chronic obstructive pulmonary disease (COPD) have flow limitation, which has deleterious side effects. If these patients are mechanically ventilated, this often results in difficult weaning. Spontaneously breathing COPD patients experience a beneficial effect of pursed lip breathing. We investigated whether in intubated COPD patients application of an external resistance could produce the same beneficial effects on breathing pattern and gas-exchange as pursed lip breathing.Methods: Ten COPD patients with flow limitation were studied during pressure support mechanical ventilation. Two types of expiratory resistances were applied: one fixed level of resistance and one with a resistive pressure decay. Each resistance was applied in 5 patients and the highest level was chosen that did not cause hyperinflation. Blood gas values and breathing pattern with and without resistance were compared.Results: With resistance 1, gas-exchange and breathing pattern did not change significantly; average PCO2 changed from 8.0 to 8.1 kPa, PO2 from 10.2 to 10.3 kPa, tidal volume from 0.380 to 0.420 l, respiratory rate from 25 to 23 bpm and inspiratory:expiratory ratio from 1:1.9 to 1:2.0. With resistance 2, gas-exchange and breathing pattern did not change significantly; average PCO2 changed from 5.8 to 6.0 kPa, PO2 from 11.1 to 12.1 kPa, tidal volume from 0.733 to 0.695 l, respiratory rate from 16 to 18 bpm and inspiratory:expiratory ratio from 1:2.3 to 1:2.9.Conclusion: In intubated COPD patients being weaned from the ventilator, application of an external resistance did not have the same beneficial effects as pursed lip breathing. [ABSTRACT FROM AUTHOR]

Strawberry and wild strawberry are among the most popular horticultural crops. Due to the development of soilless cultivation systems, the whole-year production of these economically important fruit crops is achievable even in countries with temperate climate. However, the responses of strawberry (Fragaria × ananassa Duch.) and wild strawberry (Fragaria vesca L.) to microclimate conditions in greenhouse gutter cultivation in the autumn–winter season in Poland have not been yet determined. The aim of this study was to analyze the physiological, biochemical, and biometrical responses of two cultivars of strawberry 'Ostara' and 'San Andreas' and two cultivars of wild strawberry 'Baron von Solemacher' and 'Regina' grown for 20 weeks, starting from September 17th, in controlled greenhouse conditions on coconut mats in gutters in the autumn–winter season and irradiated with sodium lamps. Strawberry 'San Andreas' produced 30% larger leaves and almost three-fold higher fresh and dry weight of biomass than 'Ostara'. The strawberry plants 'San Andreas' had a higher content (20%) of chlorophyll a and 30% of chlorophyll b than 'Ostara' plants. Generally, 'San Andreas' displayed an overall higher concentration of intercellular CO2 (about 14%) than 'Ostara' plants providing higher gas exchange processes. Photosynthetic rate amounted to 13.0 μmol·m−2·s−1 for 'San Andreas' that was almost two-fold higher than for 'Ostara'. 'San Andreas' flower and fruit productions were uniform and the six-fold higher individual fruit yield proved the excellent attributes of this cultivar to the greenhouse cultivation. Even though the productivity of the two studied wild strawberry cultivars was similar, 'Regina' showed higher values of some parameters than 'Baron von Solemacher' (40% larger leaves, 25% higher photosynthetic rate, 10% higher concentration of intercellular CO2). A high nutritional value of fruits is maintained compared to traditional open-air cultivation. [ABSTRACT FROM AUTHOR]

AbstractSoil and ecosystem trace gas fluxes are commonly measured using the dynamic chamber technique. Although the chamber pressure anomalies associated with this method are known to be a source of error, their effects have not been fully characterized. In this study, we use results from soil gas-exchange experiments and a soil CO2 transport model to characterize the effects of chamber pressure on soil CO2 efflux in an annual California grassland. For greater than ambient chamber pressures, experimental data show that soil-surface CO2 flux decreases as a nonlinear function of increasing chamber pressure; this decrease is larger for drier soils. In dry soil, a gauge pressure of 0.5 Pa reduced the measured soil CO2 efflux by roughly 70% relative to the control measurement at ambient pressure. Results from the soil CO2 transport model show that pressurizing the flux chamber above ambient pressure effectively flushes CO2 from the soil by generating a downward flow of air through the soil air-filled pore space. This advective flow of air reduces the CO2 concentration gradient across the soil–atmosphere interface, resulting in a smaller diffusive flux into the chamber head space. Simulations also show that the reduction in diffusive flux is a function of chamber pressure, soil moisture, soil texture, the depth distribution of soil CO2 generation, and chamber diameter. These results highlight the need for caution in the interpretation of dynamic chamber trace gas flux measurements. A portion of the frequently observed increase in net ecosystem carbon uptake under elevated CO2 may be an artifact resulting from the impact of chamber pressurization on soil CO2 efflux. [ABSTRACT FROM AUTHOR]

Whole plants and individual leaves of Commelina communis and Triticum aestivum were used to study the influence of changes in apoplastic Ca on the regulation of gas-exchange, in particular stomatal conductance (g) and transpiration (E). Plants grown in nutrient solution at a low concentration of Ca (1 mol m-3) were used in experiments where rapid changes in Ca concentration were induced via the rhizosphere or by direct entry into the xylem. Solutions containing Ca2+ ions were applied directly to the leaf surface and also through the cut end of detached leaves and via a xylem feeding system to attached leaves. Putative Ca-channel blockers (lanthanum chloride and verapamil hydrochloride), which are believed to deny Ca entry into the cytoplasm, were also used to provide more information about the nature of the action of Ca on the guard cells. In all the experimental systems used, the short-term application of 8 mol m-3 Ca induced reductions in both g and E, but when longer-term changes in the calcium concentrations in the xylem sap were induced through changes in Ca supply from the rhizosphere, no change in g was apparent. These experiments raise important questions about how plants with an abundant supply of calcium in the rhizosphere prevent high concentrations of apoplastic calcium from interfering in the stomatal mechanism. The data presented do not preclude the possibility that a pulse of calcium ions delivered into the xylem could be used in root--shoot communication. [ABSTRACT FROM AUTHOR]

The importance of throughflow convection of gases is recognized but the notion that convection of a nonthroughflow type might play a major role in plant aeration is challenged. It is shown that this convection discovered recently in deep-water rice, and which could operate also in almost any submerged root system, must be subordinate to diffusion in the plant's aeration process and will at best have only minimal influence m root aeration. [ABSTRACT FROM AUTHOR]

• Total yield was not affected by temperature in low-node-order pinching. • Supra-optimal daily mean temperature (30 °C) decreased tomato dry matter production. • Relative growth rate was significantly increased at 30 °C. • Carbohydrate utilization for growth and gas-exchange rate were the highest at 30 °C. • Low-node-order pinching system is expected to be suitable for hot regions. To understand the effects of supra-optimal air temperature with adequate total solar radiation on dry matter production in tomato, we quantified morphological and physiological changes in tomato growth under daily mean temperature at 30 °C. After transplanting, we grew tomato plants under a daily mean temperature of 20 °C, 25 °C, or 30 °C in a growth chamber at high light intensity provided by a LED source until the cumulative daily mean temperature (CT) reached 2000 °C. Plants were pinched when CT reached 1000 °C to remove the vegetative growth sink. Total dry matter was significantly lower at 30 °C than in the other treatments, although relative growth rate (RGR) increased with increasing temperature. An RGR increase at 30 °C was associated with greater net assimilation rate and leaf area ratio. Gross photosynthetic rate and utilization of carbohydrates for plant growth also increased with increasing daily mean temperature. At CT 2000 °C, gas-exchange rate at 30 °C was about twice as high as that at 20 °C, though they were similar at CT 1000 °C in spite of difference of daily mean temperature. Accumulation of non-structural carbohydrates in leaves and stems at 30 °C were less than those at 20 °C. We conclude that supra-optimal daily mean temperature (30 °C) increases RGR, because not only the gas-exchange rate was high, but also photosynthetic assimilates are utilized efficiently for plant growth at 30 °C. [ABSTRACT FROM AUTHOR]

• Glyphosate induced marked changes in leaf ultrastructure and promoted cell death. • Transcriptional and biochemical control of photosynthesis was impaired by glyphosate. • Glyphosate-treated plants presented a lower water use efficiency. • The few viable cells were shown to preserve their photosynthetic potential. This study aimed to assess the toxicity of glyphosate (GLY; 0, 10, 20 and 30 mg kg−1) in Solanum lycopersicum L., particularly focusing on the photosynthetic metabolism. By combining ecophysiological, ultrastructural, biochemical and molecular tools, the results revealed that the exposure of tomato plants to GLY led to alterations in leaf water balance regulation [increasing stomatal conductance (g s) and decreasing water use efficiency (WUE i) at higher concentrations] and induced slight alterations in the structural integrity of cells, mainly in chloroplasts, accompanied by a loss of cell viability. Moreover, the transcriptional and biochemical control of several photosynthetic-related parameters was reduced upon GLY exposure. However, in vivo chlorophyll fluorometry and IRGA gas-exchange studies revealed that the photosynthetic yield of S. lycopersicum was not repressed by GLY. Overall, GLY impacts cellular and subcellular homeostasis (by affecting chloroplast structure, reducing photosynthetic pigments and inhibiting photosynthetic-related genes transcription), and leaf structure, but is not reducing the carbon flow on a leaf area basis. Altogether, these results suggest a trade-off effect in which GLY-induced toxicity is compensated by a higher photosynthetic activity related to GLY-induced dysfunction in g s and an increase in mesophyll thickness/density, allowing the viable leaf cells to maintain their photosynthetic capacity. [ABSTRACT FROM AUTHOR]

Background: Existing methods for directly measuring photosynthetic capacity (Amax) have low throughput, which creates a key bottleneck for pre-breeding and ecological research. Currently available commercial leaf gas exchange systems are not designed to maximize throughput, on either a cost or time basis. Results: We present a novel multiplexed semi-portable gas exchange system, OCTOflux, that can measure Amax with approximately 4–7 times the throughput of commercial devices, despite a lower capital cost. The main time efficiency arises from having eight leaves simultaneously acclimate to saturating CO2 and high light levels; the long acclimation periods for each leaf (13.8 min on average in this study) thus overlap to a large degree, rather than occurring sequentially. The cost efficiency arises partly from custom-building the system and thus avoiding commercial costs like distribution, marketing and profit, and partly from optimizing the system’s design for Amax throughput rather than flexibility for other types of measurements. Conclusion: Throughput for Amax measurements can be increased greatly, on both a cost and time basis, by multiplexing gas streams from several leaf chambers connected to a single gas analyzer. This can help overcome the bottleneck in breeding and ecological research posed by limited phenotyping throughput for Amax. [ABSTRACT FROM AUTHOR]