Gas Exchange Measurements Research Articles

Enhancing the water use efficiency model predictions for Platycladus orientalis and Quercus variabilis: Integrating the dynamics of carbon dioxide concentration and soil water availability.

Water use efficiency (WUE) is a tracer for plants on the trade-off exchange of water and carbon dioxide between terrestrial ecosystems and the atmosphere; therefore, a dynamic investigation of WUE and its driving factors will be of great significance to optimize water and carbon fitness and predict the plants' response to climate change. In our study, a modified water use efficiency model was proposed to improve the quantification of carbon and water processes by adding a photosynthesis-gs simulation dependent on CO2 concentration and soil moisture to the photosynthetic transpiration model (noted as SMPTSB model). Actual measured water use efficiencies were respectively obtained by the gas exchange measurements (WUEge) and the δ13CWSC that defined as the carbon-heavy isotope of the water-soluble compound in leaves (WUEwsc) of three-year tree saplings of Platycladus orientalis (L.) Franco and Quercus variabilis Blume, which were cultured in an orthogonal treatment consisting of four ambient CO2 concentrations ([CO2]) and five soil volumetric water contents (SWC). Direct comparisons of the modeled and measured stomatal conductance and WUE further indicated that the modified WUE model makes carbon assimilation, stomatal conductance and WUE more sensitive to [CO2] and soil moisture. From this, the enhancement of WUE in P. orientalis and Q. variabilis saplings is expected to occur when the ambient CO2 concentration increases to 600ppm - 700ppm and the appropriate SWC reaches 60% to 80% of the field capacity for potted soil. In general, the water use efficiency model that accounts for the synergistic effects of environmental CO2 concentration and soil moisture can accurately identify the corresponding thresholds for the optimal efficiency of carbon and water use of vegetation, which is expected to provide a theoretical basis for predicting the corresponding forest management practices to address future climate change.

Exercise and cardiac rehabilitation after LVAD implantation.

Left ventricular assist devices (LVAD) have improved mortality and quality of life for patients with end-stage heart failure by providing an alternative to cardiac transplant or as a bridge to transplantation. The improvement in functional capacity however is minimal to modest depending on the right ventricular function, optimal hemodynamics on LVAD therapy, and comorbidities. There is improvement in submaximal exercise capacity but improvement in peak aerobic capacity is limited. Exercise capacity can be improved by referral to cardiac rehabilitation after LVAD implantation. Cardiac rehabilitation is safe and effective with improvement in functional capacity, and decrease in mortality and heart failure hospitalizations. Cardiopulmonary exercise testing (CPET) is a specialized exercise stress test that measures gas exchange during exercise to determine a variety of variables that have been shown to be predictive of mortality in patients undergoing cardiac transplant. CPET is valuable for prognostication and is a predictor of adverse outcomes, including right heart failure in the immediate post-LVAD implantation period, long-term mortality. CPET is an additional testing that can aid in the decision making for LVAD explantation or decommissioning.

A leaf-level field physiological tool linking non-invasive leaf gas exchange and chlorophyll fluorescence measurements applicable at larger ecophysiological scales.

A leaf-level field physiological tool linking non-invasive leaf gas exchange and chlorophyll fluorescence measurements applicable at larger ecophysiological scales.

Better safe than sorry: the unexpected drought tolerance of a wetland plant (Cyperus alternifolius L.).

A common assumption of plant hydraulic physiology is that high hydraulic efficiency must come at the cost of hydraulic safety, generating a trade-off that raises doubts about the possibility of selecting both productive and drought-tolerant herbaceous crops. Wetland plants typically display high productivity, which requires high hydraulic efficiency to sustain transpiration rates coupled to CO2 uptake. Previous studies have suggested high vulnerability to xylem embolism of different wetland plants, in line with expected trade-offs. However, some hygrophytes like Cyperus alternifolius L. can also experience prolonged periods of low water levels leading to substantial drought stress. We conducted an in-depth investigation of this species' hydraulic safety and efficiency by combining gas exchange measurements, hydraulic measurements of leaf hydraulic efficiency and safety, optical measurements of xylem vulnerability to embolism, and determination of cell turgor changes under drought. Our data confirm the high hydraulic efficiency of this wetland species, but at the same time, reveal its surprising drought tolerance in terms of turgor loss point and critical water potential values inducing xylem embolism and hydraulic failure, which were well below values inducing turgor loss and full stomatal closure. C. alternifolius emerges as a highly productive plant that is also well-equipped to tolerate drought via a combination of early stomatal closure and delayed onset of hydraulic damage. The species might represent a model plant to develop crops combining two of the most desirable traits in cultivated plants, i.e., high yield and significant drought tolerance.

The specifics of chamber measurements of greenhouse gas emissions in coastal and marine ecosystems

The article presents the results of measuring CO2 fluxes on the beach in areas with and without marine macrophytes and at the water-atmosphere boundary in Kievka Bay. Such studies were conducted for Kievka Bay for the first time. A chamber dynamic method and a laser gas analyzer were used to measure CO2 fluxes at all plots. Higher values of CO2 fluxes were noted on the beach in areas with dry beach macrophytes compared to wet beach macrophytes. Areas with macrophytes had 23 times higher values of CO2 fluxes compared to areas without beach macrophytes. To identify patterns and intensity of CO2 gas exchange between the sea and the atmosphere, long-term monitoring measurements are necessary, since there are many variable factors. When measuring gas exchange between the sea and the atmosphere, sharp short-term increases or decreases in CO2 concentration were noted on the graphs of concentration versus measurement time. This was not associated with technical failures of the gas analyzer or features of the floating chamber. This introduces difficulties in interpreting the data, since the linearity of the graph is lost and the error in the flow value increases.

Impact of exogenous rhamnolipids on plant photosynthesis and biochemical parameters under prolonged heat stress.

High temperatures severely affect plant growth and development leading to major yield losses. These temperatures are expected to increase further due to global warming, with longer and more frequent heat waves. Rhamnolipids (RLs) are known to protect several plants against various pathogens. To date, how RLs act under abiotic stresses is unexplored. In this study, we aimed to investigate whether RLs could modify Arabidopsis thaliana physiology during prolonged heat stress. Measurement of leaf gas exchange and chlorophyll fluorescence showed that heat stress reduces photosynthetic rate through stomatal limitation and reduction of photosystem II yield. Our study reported decreased chlorophyll content and accumulation of soluble sugars and proline in response to heat stress. RLs were shown to have no detrimental effect on photosynthesis and carbohydrate metabolism in all conditions. These results extend the knowledge of plant responses to prolonged heat stress.

Temperature governs the relative contributions of cuticle and stomata to leaf minimum conductance.

During periods of stomatal closure, such as drought, plant leaves continue to lose water at a rate determined by the minimum leaf conductance, gmin. Although gmin varies with temperature, less is known about what drives this variation, including how the pathways of water loss (cuticle or stomata) vary with temperature. We used gas exchange and bench drying methods to measure gmin and cuticular conductance, gcw, across a wide temperature range (20-50°C) in 11 broadleaf species. Vapour pressure deficit (VPD) covaried with temperature from 0.83 to 10.7 kPa. The dominant pathway of water loss for gmin shifted from stomatal transpiration towards cuticular transpiration as temperature increased. Leaf traits had variable, temperature-dependent relationships with gmin and gcw, with trait-conductance relationships being generally stronger at higher temperatures. Cuticular thickness varied inversely with high-temperature gcw. Simulation results showed that gcw may impact photosynthetic capacity estimates, particularly in species with low stomatal conductance. The pathways of water loss in leaves during times of stomatal closure depend strongly on temperature. This effect may have large implications for landscape-scale water balance modelling and improving gas exchange measurements. We propose variation in VPD as a potential contributing factor in gmin and gcw variation among studies.

Field integration of shoot gas-exchange and leaf chlorophyll fluorescence measurements to study the long-term regulation of photosynthesis in situ.

Understanding the diurnal and seasonal regulation of photosynthesis is an essential step to quantify and model the impact of the environment on plant function. Although the dynamics of photosynthesis have been widely investigated in terms of CO2 exchange measurements, a more comprehensive view can be obtained when combining gas-exchange and chlorophyll fluorescence (ChlF). Until now, integrated measurements of gas-exchange and ChlF have been restricted to short-term analysis using portable IRGA systems that include a fluorometer module. In this communication we provide a first-time demonstration of long-term, in situ, and combined measurements of photosynthetic gas-exchange and ChlF. We do so by integrating a new miniature PAM-fluorometer into an existing system of automated chambers to track photosynthetic gas-exchange of leaves and shoots in situ. The setup is used to track the dynamics of the light and carbon reactions of photosynthesis at a 20-minute resolution in leaves of silver birch (Betula pendula Roth) during summertime. The potential of the method is illustrated using the ratio between electron transport and net assimilation (ETR/ANET), which reflects the internal electron use efficiency of photosynthesis. The setup successfully captured the diurnal patterns in the ETR/ANET during summertime, including a large increase in noon ETR/ANET in response to a period of high temperatures and relatively low soil moisture, pointing to a drastic decrease in electron use efficiency. The observations emphasize the value of combined and long-term in situ measurements of ChlF and gas-exchange, opening new opportunities to investigate, model and quantify the regulation of photosynthesis in situ and the connection between ChlF and photosynthetic gas-exchange. The next steps, potential and limitations of the approach are discussed.

Physiological response in professional female soccer players

The aim of this study was to describe the physiological characteristics and energetic requirements of small-side games (SSG) in female players by means of ambulatory gas exchange measurements using a breath-by-breath (B × B) approach. Eight female professional soccer players participated in this study. This study was divided into two sessions: laboratory exercise testing and SSG field testing. Both tests were performed using simultaneous gas exchange measurements. The incremental ramp exercise test was performed using portable metabolic carts breath by breath (B×B) and a treadmill, to measure the maximum oxygen uptake (VO2max) and maximum heart rate (HRmax) of each player. In the SSG field test, the metabolic carts (B×B), was used during SSG to measure oxygen uptake (VO2), average heart rate (HRave), breath frequency (fB), minute ventilation (VE), energy expenditure (EE), and heart Rate and O2 Pulse (VO2/HR). Activity profiles were assessed by professional technical coaches (n = 2). A total of 152 passes were included in the four-a-side SSG analysis. Specifically, 85.53% of the total passes were categorized as successful passes and 14.47% were categorized as failed passes. VO2 during SSG was 83.90% of the VO2max, and HRave during SSG was 84.42% of the HRmax. The independent t-test showed a difference between blood lactate levels post-SSG and blood lactate after the incremental ramp-like exercise [p = .001; F = 97.294]. Four-a-side SSG have sufficient physiological demands for female players, characterized by achieving the minimum standard of physiological response with maximum aerobic capacity.

A Crop Water Stress Index for Hazelnuts Using Low-Cost Infrared Thermometers.

Incorporating data-driven technologies into agriculture presents a promising approach to optimizing crop production, especially in regions dependent on irrigation, where escalating heat waves and droughts driven by climate change pose increasing challenges. Recent advancements in sensor technology have introduced diverse methods for assessing irrigation needs, including meteorological sensors for calculating reference evapotranspiration, belowground sensors for measuring plant available water, and plant sensors for direct water status measurements. Among these, infrared thermometry stands out as a non-destructive remote sensing method for monitoring transpiration, with significant potential for integration into drone- or satellite-based models. This study applies infrared thermometry to develop a crop water stress index (CWSI) model for European hazelnuts (Corylus avellana), a key crop in Oregon, the leading hazelnut-producing state in the United States. Utilizing low-cost, open-source infrared thermometers and data loggers, we aim to provide hazelnut farmers with a practical tool for improving irrigation efficiency and enhancing yields. The CWSI model was validated against plant water status metrics such as stem water potential and gas exchange measurements. Our results show that when stem water potential is below -6 bar, the CWSI remains under 0.2, indicating low plant stress, with corresponding leaf conductance rates ranging between 0.1 and 0.4 mol m2 s-1. Additionally, un-irrigated hazelnuts were stressed (CWSI > 0.2) from mid-July through the end of the season, while irrigated plants remained unstressed. The findings suggest that farmers can adopt a leaf conductance threshold of 0.2 mol m2 s-1 or a water potential threshold of -6 bar for irrigation management. This research introduces a new CWSI model for hazelnuts and highlights the potential of low-cost technology to improve agricultural monitoring and decision-making.

Development and gas exchange of fig plants submitted to dynamized high dilutions

The productive potential of crops directly depends on their primary metabolism, for which photosynthetic efficiency is the best indicator. This study aimed to evaluate the effect of dynamized high dilutions on the development and photosynthetic efficiency of fig plants under greenhouse conditions. The treatments were Belladonna, Thuya occidentalis, and the nosode of fig leaves with rust at 30 CH (centesimal hahnemannian dilution order). Distilled water was the control treatment. The subplot consisted of fig cultivars Roxo de Valinhos and Branco Rosa Lages. Weekly sprays started 30 days after transplanting and lasted for 5 weeks. Plant height and total number of leaves were evaluated at 0, 37, 44, 51, 58, 65, 86, 100, and 114 days after transplanting. Photosynthetic efficiency was estimated at 5, 15, 30, and 50 days after the first application with an Infra-Red Gas Analyser – IRGA by measuring gas exchange: (a) CO2 assimilation rate, (b) transpiration rate, (c) stomatal conductance and (c) internal concentration of CO2 in the leaf. Water use and carboxylation efficiency were also determined. According to the data, the cultivar Roxo de Valinhos was more sensitive to the dynamized high dilutions concerning leaf emission per day and remaining leaves, and it showed a higher response to Thuya occidentalis and the nosode. Net photosynthesis increased after cumulative applications on the cultivar Roxo de Valinhos treated with Thuya and Belladonna. The dynamized high dilutions can influence plant development and photosynthesis, and Roxo de Valinhos is highly sensitive to such dilutions.

Energy balance analysis suggests that lactate is not a direct cause of the slow component of oxygen uptake kinetics.

The mechanisms of oxygen uptake ( ) slow component in the severe exercise intensity domain are still a matter of debate. We tested the hypothesis that the rate of blood lactate ([La]) accumulation above maximal lactate steady state (MLSS) is a major cause of slow component. On 13 males exercising on a cycle-ergometer, we measured gas exchanges, heart rate, and [La] during maximal incremental exercise test to determine maximal aerobic power ( max) and at constant power exercise tests at 60%, 65%, 70%, and 80% of max. Maximal was 3.19 ± 0.37l·min-1, max was 283 ± 28 W. At 60% max all variables attained steady state in all subjects. Power at MLSS was 177 ± 21 W. At 80% max a clear slow component was observed in all subjects, exercise lasted 11.3 ± 3.1min and [La] was 7.4 ± 2.2mmol at 5min and 11.5 ± 3.6mmol at 10min. The energy balance computed at 80% max resulted compatible with the principles of the energetics of muscular exercise, if we assume linear [La] increase, and thus constant metabolic power provided by [La] accumulation. Conversely, the metabolic power provided by slow component increases with time. This contrast is incompatible with the tested hypothesis that consequently must be rejected. This study excluded [La] accumulation as a main cause of slow component.

Comparing the Accuracy and Efficiency of Leaf Gas Exchange Measurements of Excised and Nonexcised Strawberry (Fragaria ×ananassa Duch. ‘Camino Real’) Leaves

Acquiring leaf gas exchange (LGE) data from field experiments is critical for numerous research endeavors. However, because of the extended time needed to perform measurements and the necessity for moving equipment, the number of leaf samples collected is often limited. To address this concern, two studies were conducted to evaluate the accuracy and efficiency of LGE measurements of excised and nonexcised strawberry leaves. Research was conducted in experimental field plots located in Lubbock, TX, USA, where ‘Camino Real’ strawberry leaves was sampled for LGE measurements, during the 2021 growing season. Using an auto program mode, two LI-6400/XT portable machines simultaneously measured the LGE of nearby selected leaves from the same plant. Measurements were recorded every 30 seconds. After 90 seconds, the petiole of one leaf was cut (excised leaf treatment), and the auto program continued for an additional 480 seconds. The results indicated that although the LGE for nonexcised leaves remained stable, excised leaf LGE changed after excision. Within 30 seconds, the postexcision stomatal conductance to water vapor (gsw) and net leaf photosynthetic rate (A) exhibited nearly 97% and 99% accuracy, respectively, of nonexcised leaf gsw and A. However, the excised LGE decrease accelerated over time, with gsw continuing to decrease by more than 5% after 43 seconds, indicating ≤95% accuracy of the gsw results. The data suggested that strawberry LGE may be measured accurately within 30 to 40 seconds after leaf excision. During a separate experiment, the mean time to complete each individual strawberry LGE measurement was 68.4 seconds (±0.9 seconds) for nonexcised leaves. Conversely, the mean time to complete each LGE measurement of excised leaves was 42.2 seconds (±0.2 seconds). Therefore, leaf excision appears to be a viable method of maintaining accuracy and increasing the sample size while collecting strawberry LGE data.

Validity and between-days reliability of two different metabolic systems for measuring gas exchange during walking

Validity and between-days reliability of two different metabolic systems for measuring gas exchange during walking

Plant Biosensors Analysis for Monitoring Nectarine Water Status.

The real-time monitoring of plant water status is an important issue for digital irrigation to increase water productivity. This work focused on a comparison of three biosensors that continuously evaluate plant water status: trunk microtensiometers (MTs), trunk time-domain reflectometry (TDR), and LVDT sensors. During the summer and autumn seasons (DOY 150-300), nectarine trees were subjected to four different consecutive irrigation periods based on the soil Management Allowed Deficit (MAD) concept, namely: MAD10 (light deficit); MAD50 (moderate deficit); MAD100 (severe deficit), and MAD0 (full irrigation). Measurements of stem water potential (Ψstem) and leaf gas exchange were recorded on representative days. A continuous measurement of the plant water status of Ψtrunk, MDS, and Ktrunk revealed the water deficits imposed on the soil. The highest water deficit observed at the end of the MAD100 period (Ψstem = -2.04 MPa and Ɵv = 17%) resulted in a minimum value of Ψtrunk (-1.81 MPa). The maximum value of MDS (408 µm) was observed earlier than that of Ψtrunk, motivated by the low sensitivity of MDS at Ψtrunk < -1.2 MPa and Ψstem < -1.5 MPa due to a decrease in the tissue elasticity of the trunk when severe water deficit conditions are reached. Both Ψtrunk and Ψstem were more dependent on soil water content, while MDS was more responsive to environmental changes. Ktrunk was the weakest indicator for determining plant water status, although when expressed as a daily fraction of depletion (KtrunkFD), it improved, evidencing a process of hysteresis. Ψtrunk showed the highest sensitivity, suggesting the potential use of MTs as a valuable biosensor for monitoring nectarine water status in digital agrosystems.

A Decline in Stomatal Conductance Is the Primary Reason for Low Photosynthesis in Veteran Pedunculate Oak Trees

Veteran trees are important elements in forests, as well as urban and suburban areas, and represent part of our cultural heritage. However, increasing age also brings a reduction in vitality. Information on tree physiological vitality can be gained by examining ecophysiological traits, such as photosynthesis, stomatal conductance, and leaf water potential. Here, we assess the effects of age on the photosynthesis and water status of 600-year-old pedunculate oak trees (Quercus robur L.) by comparing them with neighbouring 25-year-old trees. While gas exchange measurements indicated lowered photosynthesis in old trees, their maximum rates of Rubisco carboxylation and electron transport were similar to younger trees, suggesting that biochemical limitations to photosynthesis are not the reason behind their reduced vitality. Moreover, there was no difference in light-adapted and dark-adapted chlorophyll fluorescence between old and young trees. In contrast, stomatal conductance (under unlimited soil water availability) was lower, indicating increased stomatal limitations to photosynthesis in veteran trees. On the other hand, high water potential during mild summer drought conditions indicated better access to soil water in old trees, while stomatal conductance in old trees was higher than in young trees at night. A reduced ability to open and close stomata may be one of the reasons for the observed decline in veteran tree vitality, with a lowered ability to regulate stomatal conductance resulting in reduced carbon gain and unnecessarily high water loss.

Microcontroller-based water control system for evaluating crop water use characteristics

BackgroundClimate change and the growing demand for agricultural water threaten global food security. Understanding water use characteristics of major crops from leaf to field scale is critical, particularly for identifying crop varieties with enhanced water-use efficiency (WUE) and stress tolerance. Traditional methods to assess WUE are either by gas exchange measurements at the leaf level or labor-intensive manual pot weighing at the whole-plant level, both of which have limited throughput.ResultsHere, we developed a microcontroller-based low-cost system that integrates pot weighing, automated water supply, and real-time monitoring of plant water consumption via Wi-Fi. We validated the system using major crops (rice soybean, maize) under diverse stress conditions (salt, waterlogging, drought). Salt-tolerant rice maintained higher water consumption and growth under salinity than salt-sensitive rice. Waterlogged soybean exhibited reduced water use and growth. Long-term experiments revealed significant WUE differences between rice varieties and morphological adaptations represented by altered shoot-to-root ratios under constant drought conditions in maize.ConclusionsWe demonstrate that the system can be used for varietal differences between major crops in their response to drought, waterlogging, and salinity stress. This system enables high-throughput, long-term evaluation of water use characteristics, facilitating the selection and development of water-saving and stress-tolerant crop varieties.

Abstract 4139170: Relationship between hemodynamics and oxygen consumption in hypertrophic cardiomyopathy during maximal stress testing

Background: Hypertrophic cardiomyopathy (HCM) is a global heart disease with great variability in disease severity, which can lead to significant impairment of exercise capacity. In healthy populations, oxygen consumption is related to cardiac output and arteriovenous oxygen difference. We sought to determine the relationship between hemodynamics (cardiac output and stroke volume) and oxygen consumption in HCM compared to healthy controls during maximal stress testing. Aims: To evaluate associations between the trajectories of hemodynamic function and oxygen consumption in HCM compared to healthy controls. Methods: Twenty individuals with HCM (51±15 years old, body mass index (BMI): 28±3 kg/m 2 , females, n=4) and 16 healthy controls (66±7 years old, 27±6 kg/m 2 , females, n=6) were included in the present study. Participants completed a maximal-graded stress test coupled with non-invasive hemodynamic bioreactance (cardiac output, stroke volume) and gas exchange (oxygen consumption, VO 2 ) measurements. Data were analyzed in quartiles (exercise only) and phases (rest, pre-pedalling, exercise and recovery) of the maximal-graded stress test. Results: In HCM, cardiac output declined in the fourth quartile of the exercise phase of the stress test (-0.39 L/min, p &lt;0.001) whilst VO 2 increased (3.86 ml/kg/min, p &lt;0.001). There was a significant difference in the gradient of cardiac output between HCM and controls in the final quartile of the test (-1.6 vs. 18.1 L/min, p&lt;0.001). In coherence, stroke volume declined in the fourth quartile of the test (-18.4 ml, p &lt;0.01) in response to increasing VO 2 in HCM. The rates of recovery were faster in HCM compared to the control group for VO 2 (-4.3 vs -2.6 mL/second, p&lt;0.001), cardiac output (-0.03 vs -0.02 L/second, p&lt;0.001), heart rate (-0.17 vs -0.10 beats/second, p&lt;0.001), and stroke volume (-0.18 vs -0.07 L/second, p&lt;0.001). Conclusions: In HCM, cardiac output declined during the later stages of maximal stress testing whereas in controls it continued to rise, indicating impaired maximal cardiac output responses to exercise. These findings have implications for exercise prescription and training regimens in HCM suggesting avoidance of maximal exercise levels.

Validity and feasibility of four standardized aerobic fitness tests in patients with depression: A cross-sectional study

The objective of this study was to examine the validity and feasibility of four standardized aerobic fitness tests to either measure V˙ O2peak or to estimate V˙ O2max (e V˙ O2max) in patients with major depression disorder (MDD). To this end, all subjects (n = 43) performed one maximal cardiopulmonary exercise test with gas exchange measurement (CPET) on a bicycle ergometer. Additionally, three submaximal tests (Åstrand-Rhyming bicycle ergometer test [ART], Physical work capacity test [PWC], and 6-min walk test [6MWT]) were performed within two weeks in counterbalanced order. e V˙ O2max from the submaximal tests was compared to the measured V˙ O2peak from CPET using rANOVAs, Bland-Altman plots, and correlation analyses. Feasibility outcomes (e.g., perceived exertion, discomfort, pretest anxiety, etc.) were compared via rANOVAs. On group level, e V˙ O2max estimated submaximally via ART and PWC did not differ from the CPET-based V˙ O2peak, whereas there was a bias in the 6MWT, as differences of the means increased in participants with higher V˙ O2peak. During CPET, only 56% achieved a primary or secondary criterion of maximum (physiological) exertion. On the group level, V˙ O2peak and e V˙ O2max determined with the different tests showed a sufficient degree of agreement (r ≥ 0.54, ICCs≥0.66, p < 0.001), but on the individual level, marked differences occurred between CPET-based V˙ O2peak and e V˙ O2max. Three of four CRF tests (CPET, ART, PWC) proved to be feasible and could be integrated into everyday therapy and monitoring of patients with MDD as an estimate for improvement of aerobic fitness. For the exact measurement of V˙ O2peak, CPET remains the gold standard, also in patients with MDD.

Probing ozone effects on European hornbeam (Carpinus betulus L. and Ostrya carpinifolia Scop.) leaf water content through THz imaging and dynamic stomatal response

We investigated the impact of ozone exposure on Hornbeam using a novel dual approach based on Terahertz (THz) imaging in a free-air ozone exposure experiment (three ozone levels: ambient; 1.5 times ambient; twice ambient). The research aims at unraveling the physiological responses induced by elevated ozone levels on water dynamics. THz imaging unveiled dynamic changes in leaf water content, providing a non-invasive approach to leaf water monitoring. Leaf gas exchange measurements assessed stomatal responses to light variation. Our findings showcase a compelling correlation between elevated ozone levels and reduction in photosynthetic rate and impairment of stomatal function, i.e. “stomatal sluggishness”, indicative of nuanced regulatory mechanism. Stomatal sluggishness was particularly evident in Carpinus betulus (CB) compared to Ostrya carpinifolia (OC) and was linked to reduction in photosynthetic capacity. THz-based imaging techniques confirmed this result indicating a negative effect of O3 on leaf-level total water content. In addition, spatial analysis of leaf water status using these techniques also highlighted that the negative effect of O3 on water status was progressing even in less sensitive OC plants though visible foliar injury was not detected. In fact, OC showed a relative dry area of 1.6 ± 1.6 % in the control group and 3.8 ± 1.3 % under high ozone levels. THz-based imaging techniques provided a deep understanding of O3 behavior in plants and may be recommended for precision biosensing in the early detection of O3-induced damage. The integration of THz imaging and physiological analysis resulted in comprehensive understanding of Hornbeam acclimation response to ozone exposure.