Gas Exchange Dynamics Research Articles

Linking the Dynamic Response of the Carbon Dioxide-Concentrating Mechanism to Carbon Assimilation Behavior in Fremyella diplosiphon.

Cyanobacteria use a carbon dioxide (CO2)-concentrating mechanism (CCM) that enhances their carbon fixation efficiency and is regulated by many environmental factors that impact photosynthesis, including carbon availability, light levels, and nutrient access. Efforts to connect the regulation of the CCM by these factors to functional effects on carbon assimilation rates have been complicated by the aqueous nature of cyanobacteria. Here, we describe the use of cyanobacteria in a semiwet state on glass fiber filtration discs-cyanobacterial discs-to establish dynamic carbon assimilation behavior using gas exchange analysis. In combination with quantitative PCR (qPCR) and transmission electron microscopy (TEM) analyses, we linked the regulation of CCM components to corresponding carbon assimilation behavior in the freshwater, filamentous cyanobacterium Fremyella diplosiphon Inorganic carbon (Ci) levels, light quantity, and light quality have all been shown to influence carbon assimilation behavior in F. diplosiphon Our results suggest a biphasic model of cyanobacterial carbon fixation. While behavior at low levels of CO2 is driven mainly by the Ci uptake ability of the cyanobacterium, at higher CO2 levels, carbon assimilation behavior is multifaceted and depends on Ci availability, carboxysome morphology, linear electron flow, and cell shape. Carbon response curves (CRCs) generated via gas exchange analysis enable rapid examination of CO2 assimilation behavior in cyanobacteria and can be used for cells grown under distinct conditions to provide insight into how CO2 assimilation correlates with the regulation of critical cellular functions, such as the environmental control of the CCM and downstream photosynthetic capacity.IMPORTANCE Environmental regulation of photosynthesis in cyanobacteria enhances organismal fitness, light capture, and associated carbon fixation under dynamic conditions. Concentration of carbon dioxide (CO2) near the carbon-fixing enzyme RubisCO occurs via the CO2-concentrating mechanism (CCM). The CCM is also tuned in response to carbon availability, light quality or levels, or nutrient access-cues that also impact photosynthesis. We adapted dynamic gas exchange methods generally used with plants to investigate environmental regulation of the CCM and carbon fixation capacity using glass fiber-filtered cells of the cyanobacterium Fremyella diplosiphon We describe a breakthrough in measuring real-time carbon uptake and associated assimilation capacity for cells grown in distinct conditions (i.e., light quality, light quantity, or carbon status). These measurements demonstrate that the CCM modulates carbon uptake and assimilation under low-Ci conditions and that light-dependent regulation of pigmentation, cell shape, and downstream stages of carbon fixation are critical for tuning carbon uptake and assimilation.

A dynamic model of RuBP-regeneration limited photosynthesis accounting for photoinhibition, heat and water stress

Plant physiological responses to stress and subsequent damage have not been successfully integrated into leaf, plant or land surface models. Water deficit leads to a series of plant responses: stomatal closure decreases evaporative cooling leading to higher leaf temperature, which it can affect photosynthetic dissipation of absorbed energy, especially under high irradiance. Excess absorbed energy by PSII results in photoinhibition, which is not typically included when modeling photosynthesis using the Farquhar-von Caemmerer-Berry (FvCB) model. We introduce a novel approach to represent plant-atmosphere interactions: a non-steady state model of photoinhibition linked to the RuBP-regeneration component of the FvCB model that accounts for the interactions between high temperature, irradiance, and water deficits. Gas exchange and chlorophyll fluorescence dynamics showed that, under severe water stress, the maximum quantum efficiency of PSII (Fv/Fm) quickly decreases, and it takes days to recover. We found a clear relationship between maximum electron transport rate and Fv/Fm and that short-term acclimation to irradiance affected photosynthetic FvCB model parameters. Fv/Fm functioned well as a coupling variable, able to scale RuBP-regeneration limited photosynthesis parameters proportional to photoinhibition. These results indicate that plant stress, photo-inhibitory damage, and recovery can be explicitly represented when modeling photosynthesis.

Gas exchange, biomass and non-structural carbohydrates dynamics in vines under combined drought and biotic stress

BackgroundIntensity of drought stress and pest attacks is forecasted to increase in the near future posing a serious threat to natural and agricultural ecosystems. Knowledge on potential effects of a combined abiotic-biotic stress on whole-plant physiology is lacking. We monitored the water status and carbon metabolism of a vine rootstock with or without scion subjected to water shortening and/or infestation with the sucking insect phylloxera (Daktulosphaira vitifoliae Fitch). We measured non-structural carbohydrates and biomass of different plant organs to assess the stress-induced responses at the root, stem, and leaf level. Effects of watering on root infestation were also addressed.ResultsHigher root infestation was observed in drought-stressed plants compared to well-watered. The drought had a significant impact on most of the measured functional traits. Phylloxera further influenced vines water and carbon metabolism and enforced the sink strength of the roots by stimulating photosynthates translocation. The insect induced carbon depletion, reprogramed vine development, while preventing biomass compensation. A synergic effect of biotic-abiotic stress could be detected in several physiological and morphological traits.ConclusionsOur results indicate that events of water shortage favour insects’ feeding damage and increase the abundance of root nodosities. Root phylloxera infestation imposes a considerable stress to the plants which might exacerbate the negative effects of drought.

Partial liquid ventilation–induced mild hypothermia improves the lung function and alleviates the inflammatory response during acute respiratory distress syndrome in canines

Background Acute respiratory distress syndrome (ARDS), which is the severest form of pulmonary injury, is the leading cause of death in critical care. At present, the mortality remains high in ARDS. Partial liquid ventilation (PLV) using perfluorocarbon (PFC) has been proven to improve gas exchange and respiratory dynamics of the lungs during ARDS. However, PLV has not been shown to reduce the mortality of ARDS. Some studies have shown that mild hypothermia therapy can reduce lung injuries in animal models of ARDS by reducing inflammatory cytokine levels in lung tissues. However, hypothermia cannot produce a lung protection effect alone, and it may have a synergistic effect with other protective measures. To explore the possible role of PLV combined with mild hypothermia in the treatment of ARDS, in this study, we used PFC liquid ventilation to induce mild hypothermia in dogs suffering from ARDS and analyzed the effects of PFC liquid ventilation-induced mild hypothermia on the levels of inflammatory factors and lung histopathology in dogs with ARDS. The experimental dogs were randomly divided into conventional mechanical ventilation (CMV), normal temperature PFC liquid ventilation (NPLV), hypothermic PFC liquid ventilation (HPLV), and mechanical ventilation (MV) groups. After induction of ARDS, the CMV group was treated with CMV for respiratory support, the HPLV group was treated with PLV-induced mild hypothermia using 15 °C PFC and maintained the rectal temperature at 34–36 °C, the NPLV group was treated with PLV using 36 °C PFC and maintained the rectal temperature at 36–38 °C. The MV group served as the control group. Analyses of the pulmonary pathology, partial pressure of oxygen in the blood, and lung wet-dry weight ratio (W/T) of each dog revealed that PLV-induced mild hypothermia significantly increased the PaO2 values and attenuated lung injury, and there were no adverse effects on hemodynamics. Furthermore, treatment with PLV-induced mild hypothermia significantly increased the expression of the anti-inflammatory factor IL-10 in bronchoalveolar lavage fluid (BALF) and attenuated the expression of interleukin (IL-6) and tumor necrosis factor-α (TNF-α) in peripheral blood and in lung BALF. Moreover, the results showed that the expression of myeloperoxidase (MPO) and NF-κB p65 in lung tissues was significantly decreased by PLV-induced mild hypothermia compared with NPLV and CMV. Our results indicated that PLV combined with mild hypothermia can provide protection against oleic acid-induced ARDS in dogs.

СОХРАНЕНИЕ ДЕКОРАТИВНЫХ КАЧЕСТВ СРЕЗКИ РОЗЫ (ROSA HYBRIDA)

The purpose of this work was to study the post-harvest physiology of cut roses (R. hybrida). The objects of study were the most popular varieties in floristics: Magady, Vendella, Red Naomi, First Red, Grandgala. Studies were carried out in the autumn-winter periods of 2016- 2018 on leafy flowering shoots in laboratory with natural diffused light at an air temperature of 18-20 °C. Sampling was carried out at the stages of half-release, complete dissolution, the beginning and completion of the aging of flowers. The study in the gas exchange dynamics of cut rose flower shoots using the infrared gas analyzer LI — COR 6400RX showed a decrease in the intensity of photosynthesis and maintaining a high level of transpiration intensity and stomatal conduction of the leaf with the development and aging of the flower. The high intensity of transpiration and the large leafiness of the shoot make it difficult to maintain water status, accelerate aging and the loss of the decorative qualities of the flower. Pulsating treatment with silver thiosulfate (4 mM AgNO3: 32 mM NaS2O3) was used as inhibitor of ethylene synthesis, and 1 μl L–1 1-methylcyclopropene (1- MCP) was inhibitor of ethylene sensitivity. The results of the use of the inhibitor method allow us to conclude that ethylene is involved in the regulation of only the final stages of flower aging in roses. As trigger of the aging process can be the threshold effect of one or several gradual biochemical processes associated with the mobilization of nutrients. Visible signs of aging are preceded by impaired membrane stability. The commercial drug Chrysal does not ensure the natural development of the flower, but only slightly retards wilting. The growing conditions and storage of cut roses should ensure the active functioning of the stomatal apparatus, preventing water stress in the post-harvest period. Its consequence consists not only in the loss of turgidity of the petals, but also in accelerating aging due to the accumulation of ethylene.

Quantifying wetland plant vertical root distribution for estimating the Interface with the anoxic zone

Plant roots control many important interactions in the wetland anoxic zone such as carbon deposition, gas exchange, and nutrient dynamics, yet few studies document the vertical depth distribution of fine roots which mediates these interactions. Excavated root systems of a wetland sedge and shrub were scanned. Utilizing Root System Analyzer, normalized root length per 5 cm depth interval were quantified for 10 samples of each species. Utilizing bootstrapping, root length per depth interval for each root class was fitted to a density distribution function and matched to water table depth. Vertical root length distributions varied by root class, with shrub fine roots constrained to a narrow depth range. Between 1999 and 2010, the interface with the anoxic zone can vary by a factor of four between wet and dry years. Compared to estimates of root vertical distribution based on biomass, this study indicates a considerably higher portion of the fine roots occur in anoxic soil. Accurately quantifying the spatial distribution of the fine roots, root tips, and other sites associated with exudation is crucial for determining the strength of root-methanogen interactions.

Ventilation‐perfusion ratio: A Mathematical Approach for Gas Exchange in the Lungs

Chronic pulmonary diseases and respiratory infections remained as one of the most morbid and deadliest diseases in the world. Airway and environment play an important role in the etiology of these pathologies. The balance between oxygen and carbon dioxide exchange is the pillar of the respiratory system. The ventilation ‐ perfusion ratio (VPR) determines the efficiency of gas exchange in different areas of the lung. For a long time the lung was assumed to be divided in three regions that would have homogenous VPR. Recently it was established that the VPR changes in a more heterogeneous fashion. The aim of this project is to understand the gas exchange in each alveoli using a mathematical model that produce the VPR architecture based on airways architecture. The model assumed mass balance, the ideal gas law and diffusional forces. Parameters for the model were determined according to data obtained in the literature and their correspondent mathematical calculus. The model was implemented in MATLAB (The MathWorks®, Inc.)and the equations were solved to steady state. The model predicted gas concentrations and flows in different lung segments. We were able to model healthy an pathological situations. In addition, we also simulated environmental influence in the small airways. The mathematical model was helpful to understand the gas exchange dynamics. It could be used to predict the interaction between ventilation and perfusion under different conditions, giving the possibility to estimate the efficacy of medical intervention. It can also shed some light on how to prevent anddecrease the incidence of lung diseases.Support or Funding InformationDepartment of Biomedical Engineering, Universidad de los Andes, Bogota, ColombiaThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A Method for the Evaluation of Anaerobic Threshold Based on Heart Rate Dynamics during Incremental Exercise Test and Recovery

A new graphical method for determining the anaerobic threshold (AT), which has been experimentally tested in testing the maximal aerobic capacity in 46 cyclic sports athletes (mean age, 20.3 ± 3.6 years; body weight, 68.3 ± 10.4 kg). The gas exchange indices, the heart rate, the time of onset (from the beginning of the test) of AT by pulmonary gas exchange ratios, the non-metabolic CO2 excess, the concentration of lactate in capillary blood, and the time of onset of AT determined by the proposed graphical method by the parameters of the pulsogram obtained during the test and 10-min recovery were determined. Two different protocols of load change—the incremental ramp test on a treadmill and the incremental step test on a bicycle ergometer—were used. Regardless of the protocol and the load type, statistical analysis revealed no significant differences between the results of AT measurements in the same athletes by the gas exchange and lactate dynamics indices, on the one hand, and by using the graphical method by the pulsogram parameters, on the other hand. In the test with a stepwise increase in load on a bicycle ergometer, as well as in the test with a smoothly increasing load on a running treadmill, the indices obtained at the AT that was determined by using the graphical method highly correlated with the indices obtained at the AT that was determined by analyzing the dynamics of pulmonary ventilation, non-metabolic CO2 excess, and lactate concentration (p < 0.05). The proposed method does not require the use of sophisticated equipment and invasive procedures and can be widely used in sports and fitness practice.

Transcriptomic dynamics provide an insight into the mechanism for silicon-mediated alleviation of salt stress in cucumber plants

Salinity decreases the yield and quality of crops. Silicon (Si) has been widely reported to have beneficial effects on plant growth and development under salt stress. However, the mechanism is still poorly understood. In an attempt to identify genes or gene networks that may be orchestrated to improve salt tolerance of cucumber plants, we sequenced the transcriptomes of both control and salt-stressed cucumber leaves in the presence or absence of added Si. Seedlings of cucumber ‘JinYou 1’ were subjected to salt stress (75 mM NaCl) without or with addition of 0.3 mM Si. Plant growth, photosynthetic gas exchange and transcriptomic dynamics were investigated. The results showed that Si addition improved the growth and photosynthetic performance of cucumber seedlings under salt stress. The comparative transcriptome analysis revealed that Si played an important role in shaping the transcriptome of cucumber: the expressions of 1469 genes were altered in response to Si treatment in the control conditions, and these genes were mainly involved in ion transport, hormone and signal transduction, biosynthetic and metabolic processes, and stress and defense responses. Under salt stress alone, 1482 genes with putative functions associated with metabolic processes and responses to environmental stimuli have changed their expression levels. Si treatment shifted the transcriptome of salt-stressed cucumber back to that of the control, as evidenced that among the 708 and 774 genes that were up- or down-regulated under salt stress, a large majority of them (609 and 595, respectively) were reverted to the normal expression levels. These results suggest that Si may act as an elicitor to precondition cucumber plants and induce salt tolerance. The study may help us understand the mechanism for silicon-mediated salt tolerance and provide a theoretical basis for silicon application in crop production in saline soils.

Aeration strategy at birth influences the physiological response to surfactant in preterm lambs

BackgroundThe influence of pressure strategies to promote lung aeration at birth on the subsequent physiological response to exogenous surfactant therapy has not been investigated.ObjectivesTo compare the effect of sustained inflation...

Functional relationships between hydraulic traits and the timing of diurnal depression of photosynthesis.

The hydraulic coordination along the water transport pathway helps trees provide adequate water supply to the canopy, ensuring that water deficits are minimized and that stomata remain open for CO2 uptake. We evaluated the stem and leaf hydraulic coordination and the linkages between hydraulic traits and the timing of diurnal depression of photosynthesis across seven evergreen tree species in the southern Andes. There was a positive correlation between stem hydraulic conductivity (ks ) and leaf hydraulic conductance (KLeaf ) across species. All species had similar maximum photosynthetic rates (Amax ). The species with higher ks and KLeaf attained Amax in the morning, whereas the species with lower ks and KLeaf exhibited their Amax in the early afternoon concurrently with turgor loss. These latter species had very negative leaf water potentials, but far from the pressure at which the 88% of leaf hydraulic conductance is lost. Our results suggest that diurnal gas exchange dynamics may be determined by leaf hydraulic vulnerability such that a species more vulnerable to drought restrict water loss and carbon assimilation earlier than species less vulnerable. However, under stronger drought, species with earlier CO2 uptake depression may increase the risk of hydraulic failure, as their safety margins are relatively narrow.

Chitosan-elicited defense responses in Cucumber mosaic virus (CMV)-infected tomato plants

The control of plant diseases by inducing plant resistance responses represents an interesting solution to avoid yield losses and protect the natural environment. Hence, the intertwined relationships between host, pathogen and inducer are increasingly subject of investigations. Here, we report the efficacy of chitosan-elicited defense responses in Solanum lycopersicum var. cerasiforme plants against Cucumber mosaic virus (CMV). Chitosan was applied via foliar spray before the CMV inoculation to verify its effectiveness as a preventive treatment against the viral infection. Virus accumulation, photosynthetic performance, as well as genes encoding for proteins affecting resistance responses and biosynthetic pathways, were investigated. It was observed a significant reduction of CMV accumulation in chitosan-treated plants that were successively infected with CMV, compared to only CMV-infected ones (up to 100%). Similarly, a positive effect of chitosan on gas exchange dynamics was revealed. The analysis of gene expression (CEVI-1, NPR1, PSY2 and PAL5) suggested the occurrence of chitosan-induced, systemic acquired resistance-related responses associated with a readjustment of the plant’s oxidative status. In addition, the absence of deleterious symptoms in chitosan-treated successively CMV-infected plants, confirmed that chitosan can be used as a powerful control agent. Our data indicate that chitosan, when preventively applied, is able to elicit defense responses in tomato to control CMV infection. Such finding may be recommended to protect the tomato fruit yields as well as other crops.

HydroShoot: a functional-structural plant model for simulating hydraulic structure, gas and energy exchange dynamics of complex plant canopies under water deficit—application to grapevine (Vitis vinifera)

AbstractThis paper presents HydroShoot, a leaf-based functional-structural plant model (FSPM) that simulates gas exchange rates of complex plant canopies under water deficit conditions. HydroShoot is built assuming that simulating both the hydraulic structure of the shoot together with the energy budget of individual leaves is the asset for successfully scaling-up leaf to canopy gas exchange rates. HydroShoot includes three interacting modules: hydraulic, which calculates the distribution of xylem water potential across shoot hydraulic segments; energy, which calculates the complete energy budget of individual leaves; and exchange, which calculates net carbon assimilation and transpiration rates of individual leaves. HydroShoot was evaluated on virtual and real grapevines having strongly contrasted canopies, under well-watered and water deficit conditions. It captured accurately the impact of canopy architecture and soil water status on plant-scale gas exchange rates and leaf-scale temperature and water potential. Both shoot hydraulic structure and leaf energy budget simulations were, as postulated, required to adequately scaling-up leaf to canopy gas exchange rates. Notwithstanding, simulating shoot hydraulic structure was found more necessary to adequately performing this scaling task than simulating leaf energy budget. That is, the intra-canopy variability of leaf water potential was a better predictor of the reduction of whole plant gas exchange rates under water deficit than the intra-canopy variability of leaf temperature. We conclude that simulating the shoot hydraulic structure is a prerequisite if FSPMs are to be used to assess gas exchange rates of complex plant canopies as those of grapevines. Finally, HydroShoot is available through the OpenAlea platform (https://github.com/openalea/hydroshoot) as a set of reusable modules.

Riverine carbon dioxide evasion along a high-relief watercourse derived from seasonal dynamics of the water-atmosphere gas exchange

The high-relief catchment of the Tavignanu River (Corsica Island, France) with an elevation range from sea level to 2622 m above sea level was investigated for its riverine carbon budget and stable carbon isotopes. Major riverine dissolved inorganic carbon (DIC or TCO2) sources depended on seasons and sub-catchment lithology. In winter δ13CDIC values of −2 to −7‰ (VPDB) indicated influences of atmospheric CO2. δ13CDIC values decreased gradually to values between −9 and −12‰ in July, which indicates elevated soil CO2 contribution. An observed downstream increase in the total amount of carbon species correlated with inputs from carbonate bearing tributaries and evaporation effects in summer. Main channel partial pressure of CO2 (pCO2) was seasonally highly variable in the upper silicate catchment and the lower coastal plain, where summer values exceed up to six times atmospheric levels. During winter, the central section of the Tavignanu River was found to be undersaturated with respect to atmospheric CO2 levels. The median values for main channel pCO2 were below atmospheric levels in winter and spring and above in summer and autumn. The annual carbon flux across the air-water boundary (FCO2) along the Tavignanu River was calculated with (0.77 ± 0.24) Gg C yr−1, which is about seven times higher than the riverine TCO2 transport to the sea of about 0.11 Gg C yr−1. While large sections of the river experienced year-round atmospheric CO2 uptake or equilibrium, the river as a whole was a small but continuous net source of carbon to the atmosphere. This underlines the important, but so far not well-constrained, contributions of smaller streams and rivers to the terrestrial carbon flux and the need of incorporating them into future global carbon cycle models.

Modeling Pulmonary Gas Exchange and Single-Exhalation Profiles of Carbon Monoxide.

Exhaled breath carbon monoxide (eCO) is a candidate biomarker for non-invasive assessment of oxidative stress and respiratory diseases. Standard end-tidal CO analysis, however, cannot distinguish, whether eCO reflects endogenous CO production, lung diffusion properties or exogenous sources, and is unable to resolve a potential airway contribution. Coupling real-time breath gas analysis to pulmonary gas exchange modeling holds promise to improve the diagnostic value of eCO. A trumpet model with axial diffusion (TMAD) is used to simulate the dynamics of CO gas exchange in the respiratory system and corresponding eCO concentrations for the first time. The mass balance equation is numerically solved employing a computationally inexpensive routine implementing the method of lines, which provides the distribution of CO in the respiratory tract during inhalation, breath-holding, and exhalation with 1 mm spatial and 0.01 s temporal resolution. Initial estimates of the main TMAD parameters, the maximum CO fluxes and diffusing capacities in alveoli and airways, are obtained using healthy population tissue, blood and anatomical data. To verify the model, mouth-exhaled expirograms from two healthy subjects, measured with a novel, home-built laser-based CO sensor, are compared to single-exhalation profiles simulated using actual breath sampling data, such as exhalation flow rate (EFR) and volume. A very good agreement is obtained in exhalation phases I and III for EFRs between 55 and 220 ml/s and after 10 and 20 s of breath-holding, yielding a unique set of TMAD parameters. The results confirm the recently observed EFR dependence of CO expirograms and suggest that measured end-tidal eCO is always lower than alveolar and capillary CO. Breath-holding allows the observation of close-to-alveolar CO concentrations and increases the sensitivity to the airway TMAD parameters in exhalation phase I. A parametric simulation study shows that a small increase in airway flux can be distinguished from an increase in alveolar flux, and that slight changes in alveolar flux and diffusing capacity have a significantly different effect on phase III of the eCO profiles.

Testing an optimality-based model of rooting zone water storage capacity in temperate forests

Abstract. Rooting zone water storage capacity Sr is a crucial parameter for modeling hydrology, ecosystem gas exchange and vegetation dynamics. Despite its importance, this parameter is still poorly constrained and subject to high uncertainty. We tested the analytical, optimality-based model of effective rooting depth proposed by Guswa (2008, 2010) with regard to its applicability for parameterizing Sr in temperate forests. The model assumes that plants dimension their rooting systems to maximize net carbon gain. Results from this model were compared against values obtained by calibrating a local water balance model against latent heat flux and soil moisture observations from 15 eddy covariance sites. Then, the effect of optimality-based Sr estimates on the performance of local water balance predictions was assessed during model validation. The agreement between calibrated and optimality-based Sr varied greatly across climates and forest types. At a majority of cold and temperate sites, the Sr estimates were similar for both methods, and the water balance model performed equally well when parameterized with calibrated and with optimality-based Sr. At spruce-dominated sites, optimality-based Sr were much larger than calibrated values. However, this did not affect the performance of the water balance model. On the other hand, at the Mediterranean sites considered in this study, optimality-based Sr were consistently much smaller than calibrated values. The same was the case at pine-dominated sites on sandy soils. Accordingly, performance of the water balance model was much worse at these sites when optimality-based Sr were used. This rooting depth parameterization might be used in dynamic (eco)hydrological models under cold and temperate conditions, either to estimate Sr without calibration or as a model component. This could greatly increase the reliability of transient climate-impact assessment studies. On the other hand, the results from this study do not warrant the application of this model to Mediterranean climates or on very coarse soils. While the cause of these mismatches cannot be determined with certainty, it is possible that trees under these conditions follow rooting strategies that differ from the carbon budget optimization assumed by the model.

Modeling Tissue and Blood Gas Kinetics in Coastal and Offshore Common Bottlenose Dolphins, Tursiops truncatus.

Bottlenose dolphins (Tursiops truncatus) are highly versatile breath-holding predators that have adapted to a wide range of foraging niches from rivers and coastal ecosystems to deep-water oceanic habitats. Considerable research has been done to understand how bottlenose dolphins manage O2 during diving, but little information exists on other gases or how pressure affects gas exchange. Here we used a dynamic multi-compartment gas exchange model to estimate blood and tissue O2, CO2, and N2 from high-resolution dive records of two different common bottlenose dolphin ecotypes inhabiting shallow (Sarasota Bay) and deep (Bermuda) habitats. The objective was to compare potential physiological strategies used by the two populations to manage shallow and deep diving life styles. We informed the model using species-specific parameters for blood hematocrit, resting metabolic rate, and lung compliance. The model suggested that the known O2 stores were sufficient for Sarasota Bay dolphins to remain within the calculated aerobic dive limit (cADL), but insufficient for Bermuda dolphins that regularly exceeded their cADL. By adjusting the model to reflect the body composition of deep diving Bermuda dolphins, with elevated muscle mass, muscle myoglobin concentration and blood volume, the cADL increased beyond the longest dive duration, thus reflecting the necessary physiological and morphological changes to maintain their deep-diving life-style. The results indicate that cardiac output had to remain elevated during surface intervals for both ecotypes, and suggests that cardiac output has to remain elevated during shallow dives in-between deep dives to allow sufficient restoration of O2 stores for Bermuda dolphins. Our integrated modeling approach contradicts predictions from simple models, emphasizing the complex nature of physiological interactions between circulation, lung compression, and gas exchange.

Relationships between fruit growth and oil accumulation with simulated seasonal dynamics of leaf gas exchange in the olive tree

Carbohydrates availability, which are directly related to photosynthesis (AN), and turgor are the main determinants of fruit growth. Since stomatal conductance (gs) is the main limiting factor of AN in fruit trees in most environments, and is strongly regulated by turgor, its measurement is pivotal to understanding fruit growth dynamics. Despite its relevance, the use of gs to estimate AN faces the major limitation of being difficult to measure in an automated and continuous manner. Based on these observations, and considering the control that the stomata exert on transpiration, and thus on sap flux density (Js) under conditions of high coupling to the atmosphere, we conducted a multi-faceted experiment in olive trees. The main objective was to assess the use of continuously modelled AN, derived using a simulated gs, as a tool to study fruit growth and oil accumulation and other components of vegetative above-ground growth (leaf area and number of shoot internodes) in a super-high-density olive orchard under different irrigation levels. Sixteen olive trees under four different irrigation treatments (two control and two deficit irrigated, with one and two drip lines each) were continuously monitored with Js sensors from May to November 2016. Gas exchange, fruit growth, number of shoot internodes and leaf area were measured periodically. Stomatal conductance was empirically simulated through Js, and AN was modelled using previously simulated gs and a biochemical model of photosynthesis. Results showed that AN can be accurately modelled from simulated gs, obtained in turn from Js measurements divided by pressure deficit. Moreover, the approach was shown to be sensitive enough to infer the response of gs and AN to soil water content and vapour pressure deficit. Interestingly, accumulated AN was significantly related to fruit growth and oil content for all the irrigation treatments which determine the slope of these relations. In contrast, the relationship with leaf area was only significant for the control irrigation treatments, where the number of shoot internodes increased significantly more than in the water-stressed trees. Our results show that under water stress conditions trees prioritize fruit growth and oil content accumulation over vegetative growth, suggesting a higher sink strength for reproductive growth than for vegetative growth. We conclude that the use of sap flow and the proposed approach provides reliable gs and AN data, and allows the modelling of the relations between carbon assimilation and allocation, which are helpful to estimate fruit growth.

Feasibility of automatic ventilation technology for sea freight ofProteacut flower products

Advances in cold storage and transport technologies have seen the development of automatic ventilation technology and dynamic controlled atmosphere (DCA). Instead of using the commonly used fixed, open air exchange ventilation (AirEx) at 15,000 L fresh air h(-1) during shipping of Proteaceae stems, the new technologies restrict ventilation to gas concentrations that are near the set limits. Ventilation only occurs at O-2 levels near the lower O-2 limit (LOL) and at levels below the CO2 toxicity limit of the products. The gas exchange dynamics and ventilation requirements of sea freighted Protea cut flowers from South Africa (SA) are largely unknown, which has been a limiting factor to the introduction of automatic ventilation as an alternative within sea freight shipping. Furthermore, the suitability of current sea freight technology for Proteaceae cut flowers that are shipped from SA to Europe is under question due to inconsistencies in product quality upon arrival at their markets. The low storage temperature, AirEx ventilation and lengthy cold storage period have been identified as possible causes of quality loss during sea freight. The feasibility of the use of automatic ventilation technology during exports to distant markets was evaluated by determining the LOL values of the Protea cut flower products when stored at low O-2 concentration and assessing the toxicity tolerance in high CO2 atmosphere. Determination of the LOL was done using a fluorescence interactive response monitor (FIRM) sensor attached to a DCA system. High CO2 tolerance was tested by increasing the CO2 concentration stepwise from 5 to 15% CO2 atmospheric concentration (5-10-15% CO2). The LOL values of the products ranged from 0.08-0.25% O-2. AirEx atmosphere led to higher moisture loss than high CO2 atmosphere, with insignificant differences between AirEx and low O-2 atmosphere. The products stored in AirEx and high CO2 atmospheres had comparable flower head and leaf quality. The flower head and leaf quality of products stored in low O-2 was better than that of products stored in AirEx atmosphere.

A Mathematical Approach for Gas Exchange in the Lungs; Balance Between Ventilation and Perfusion

IntroductionChronic pulmonary diseases and respiratory infections remain as one of the most morbid and deadliest diseases in the world. Airway and environment play an important role in the etiology of these pathologies. The balance between oxygen and carbon dioxide exchange is the pillar of the respiratory system. The aim of this project is to understand the gas exchange in the lungs using a mathematical model that describes the dynamics in each alveoli, in order to evaluate the relationship between ventilation and perfusion.MethodsA mathematical model was design based on the alveoli gas exchange and its relationship between ventilation and perfusion (V/Q). So, the lungs were divided into 9 segments, each one with different ratio according to their relative exchange area and the anatomical and physiological characteristics. The model assumed mass balance for O2 and CO2 and ideal gas law. Parameters for the model were determined according to data obtained in the literature. The model was implemented in MATLAB (The MathWorks®, Inc.) and the equations were solved to steady state.ResultsThe model predicted gas concentrations and flows in different lung segments. There was an evident strong association between V/Q, and its mechanisms to compensate. The model showed the behavior of lungs with and without disease. One of the most important outcomes was the evidence of enviromental influence (i.e. altitude, polution) in the imparment of the small airways and its association with the cardiovascular system.ConclusionThe mathematical model was helpful to understand the gas exchange dynamics. The model can be used to predict the interaction between ventilation and perfusion under different conditions, giving the possibility to estimate the efficacy of medical intervention. It can also shed some light on how to prevent and decrease the incidence of lung diseases.Support or Funding InformationResearch Group in Mathematical and Computational Biology (BIOMAC), Department of Biomedical Engineering, Universidad de los Andes, Colombia.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.