Gas Exchange Measurements Research Articles

Frozen mountain pine needles: The endodermis discriminates between the ice-containing central tissue and the ice-free fully functional mesophyll.

Conifer (Pinaceae) needles are the most frost-hardy leaves. During needle freezing, the exceptional leaf anatomy, where an endodermis separates the mesophyll from the vascular tissue, could have consequences for ice management and photosynthesis. The eco-physiological importance of needle freezing behaviour was evaluated based on the measured natural freezing strain at the alpine treeline. Ice localization and cellular responses to ice were investigated in mountain pine needles by cryo-microscopic techniques. Their consequences for photosynthetic activity were assessed by gas exchange measurements. The freezing response was related to the microchemistry of cell walls investigated by Raman microscopy. In frozen needles, ice was confined to the central vascular cylinder bordered by the endodermis. The endodermal cell walls were lignified. In the ice-free mesophyll, cells showed no freeze-dehydration and were found photosynthetically active. Mesophyll cells had lignified tangential cell walls, which adds rigidity. Ice barriers in mountain pine needles seem to be realised by a specific lignification patterning of cell walls. This, additionally, impedes freeze-dehydration of mesophyll cells and enables gas exchange of frozen needles. At the treeline, where freezing is a dominant environmental factor, the elaborate needle freezing pattern appears of ecological importance. This article is protected by copyright. All rights reserved.

CO<sub>2</sub> Demand-Supply Coordination in Photosynthesis Reflecting the Plant-Environment Interaction: Extension and Parameterization of Demand Function and Supply Function

Photosynthesis consists of a biochemical process named demand and a CO2 diffusion process named supply function. The intersection (Ci, An) at equal to the demand function and the supply function reflects a steady state of the plant subjected to the environment. The intersections of these demand-supply functions under different photosynthetically active radiation (PAR) can be fitted to a regression line (names DSF) in which slope (ΔAn/ΔCi) can be defined as dsf. We found that DSF information was embedded in both Laisk method (CO2 response curve (A/Ci) measured at three sub-saturated PARs, and their intersections were used to estimate daytime respiration (Rd), and CO2 compensation point (Ci*) and light response curve measurements, which could be used to estimate dsf values. This study investigated the relationship between dsf and the parameters related to the biochemical process and the CO2 diffusion process of photosynthesis. The results showed that dsf was negatively correlated with gs, apparent carboxylation efficiency, and apparent quantum yield. This suggests that DSF may coordinate the influence of environmental conditions (light, CO2 and water) on photosynthesis in the biochemical and CO2 diffusion process. Moreover, dsf was independent of gas exchange measurement conditions and showed species specificity. In conclusion, we speculated that dsf seems to be a comprehensive parameter that might be related to the intrinsic adaptation mechanism of plants to environmental conditions. We proposed an auxiliary line perpendicular to the DSF and used it to improve the stability of Ci* and Rd estimated from the Laisk dataset.

Influence of Environmental Conditions on Carbon and Water Exchange Processes in Aucuba japonica Thunb.

In the context of climate change and deterioration of environmental conditions in urbanized regions, the study of the ecophysiological features of woody plants in order to select them for effective landscaping is of particular relevance. In this paper, the influence of abiotic factors on the daily variability of CO2/H2O gas exchange of Aucuba japonica Thunb., 1783 during the growing season on the Southern Coast of the Crimea is investigated. A photosynthesis monitor RTM-48A and a phytomonitor PM-11z (Bio Instruments S.R.L., Moldova) were used to measure gas exchange and environmental parameters. The analysis of the seasonal dynamics of carbon dioxide gas exchange showed a high sensitivity of the processes of carbon and water exchange of A. japonica to the prevailing environmental conditions, which cause fluctuations in the value of the daily carbon dioxide absorption more than four times. The preservation of the positive carbon balance of A. japonica under hydrothermal stress indicates the significant potential of plants for optimizing the urban ecosystems of the southern regions of Russia. Based on the revealed relationships a nonlinear regression equation is constructed, which can be used to predict the assimilation activity of A. japonica under current environmental conditions and expected climate changes.

Foliar-applied potassium triggers soil potassium uptake by improving growth and photosynthetic activity of wheat and maize

Foliar fertilization is an important agricultural practice. How crop plants considerably response to small amounts of foliar-applied minerals is not fully understood. In this study, we tested whether foliar-applied potassium (K) stimulates soil K uptake by plant roots. Firstly, K uptake from nutrient solution by wheat seedling was investigated with and without foliar application of K. To dissect net K uptake, quantified amount of foliar-applied K (∼19.2 mg pot−1), and K uptake by non-foliar-fertilized plants was subtracted from whole plant K uptake (foliar-treated). In the second set of experiment, maize was grown in soil, and 2% K2SO4 (∼45.4 mg K pot−1) was foliar-applied to dissect soil indigenous K uptake. In addition to elevated K level in both crops, the net K uptake via wheat and maize roots quantified ∼23% and 55%, respectively higher with foliar application of K. It is coupled with improving phenotypic observations, comprising root biomass (32–56%), root-to-shoot ratios (7–38%), and water contents (13–15%) by plotting multivariate analysis. Further, the elevated leaf gas exchange measurements and chlorophyll contents by 10% in wheat and 14% in maize ensured the optimum photosynthetic activity in foliar-applied seedlings. Notably, after crop harvesting, ∼10% lower biological available K in the soil of foliar-applied maize was found. In sum, our findings provide scientific basis that foliar K fertilization improves soil K uptake by wheat, maize, and probably, closely related to cereal crops. It also suggests a novel aspect for further investigation to understand the underlying signaling pathway(s).

Short- and long-term responses of leaf day respiration to elevated atmospheric CO2.

Evaluating leaf day respiration rate (RL), which is believed to differ from that in the dark (RDk), is essential for predicting global carbon cycles under climate change. Several studies have suggested that atmospheric CO2 impacts RL. However, the magnitude of such an impact and associated mechanisms remain uncertain. To explore the CO2 effect on RL, wheat (Triticum aestivum) and sunflower (Helianthus annuus) plants were grown under ambient (410 ppm) and elevated (820 ppm) CO2 mole fraction ([CO2]). RL was estimated from combined gas exchange and chlorophyll fluorescence measurements using the Kok method, the Kok-Phi method, and a revised Kok method (Kok-Cc method). We found that elevated growth [CO2] led to an 8.4% reduction in RL and a 16.2% reduction in RDk in both species, in parallel to decreased leaf N and chlorophyll contents at elevated growth [CO2]. We also looked at short-term CO2 effects during gas exchange experiments. Increased RL or RL/RDk at elevated measurement [CO2] were found using the Kok and Kok-Phi methods, but not with the Kok-Cc method. This discrepancy was attributed to the unaccounted changes in Cc in the former methods. We found that the Kok and Kok-Phi methods underestimate RL and overestimate the inhibition of respiration under low irradiance conditions of the Kok curve, and the inhibition of RL was only 6%, representing 26% of the apparent Kok effect. We found no significant long-term CO2 effect on RL/RDk, originating from a concurrent reduction in RL and RDk at elevated growth [CO2], and likely mediated by acclimation of nitrogen metabolism.

Grapevine leaf physiology and morphological characteristics to elevated CO2 in the VineyardFACE (Free air Carbon dioxide Enrichment) experiment.

Atmospheric carbon dioxide (CO2) concentration has continuously increased since pre-industrial times and has currently reached an average growth rate of 2.3 ppm per year. For the majority of plant species elevated CO2 (eCO2) improves photosynthesis and thus plant biomass production. To investigate the effects of eCO2 on leaf physiology and morphological leaf characteristics two Vitis vinifera L. cultivars, Riesling and Cabernet Sauvignon, grown in the VineyardFACE (Free Air Carbon dioxide Enrichment) system were used. The VineyardFACE is located at Geisenheim, Rheingau comparing future atmospheric CO2-concentrations (eCO2, predicted for the mid-21st century) with current ambient CO2-conditions (aCO2). Experiments were operated under rain-fed conditions for two consecutive years (2015 and 2016). For both varieties and CO2 treatments, leaf gas exchange measurements were performed as well as measures of epidermal flavonoid (Flav) and leaf chlorophyll (Chl) indices by using a portable leaf clip. Furthermore, leaves were sampled for spectrophotometric analysis of the leaf pigments chlorophyll a (Chl a), chlorophyll b (Chl b) and carotenoid (Car). Additionally, leaf cross-sections were produced as permanent preparations to investigate morphological characteristics of the leaf structure. Both cultivars did not differ in leaf chlorophyll meter readings or leaf pigments between the two CO2 treatments while net assimilation was highly stimulated under elevated CO2 for both seasons. Differences found in leaf cross-sections were detected in palisade parenchyma and epidermal thickness of Cabernet Sauvignon under eCO2, whereas Riesling net assimilation increased by 40% under a 20% CO2 enrichment while remaining unaffected in different leaf layer thickness. The observed results within grapevine leaf tissues provide insights to seasonal adaptation strategies of grapevines under elevated CO2 concentrations predicted in future.

Effect of animal activity and air temperature on heat production, heart rate, and oxygen pulse in lactating Holstein cows

A linear relationship between heart rate (HR) and oxygen consumption (VO2) has been reported in homeothermic animals, indicating that is possible to estimate heat production through HR measurements. This relationship may depend on the animal activity and environmental conditions. The main objective of the present study was to evaluate the effect of the air temperature and animal posture and activity on heat production and VO2 in relation to HR. In addition, as a secondary objective, the energy cost of eating and ruminating versus idling and standing versus lying down was determined. Twelve Holstein lactating cows were housed inside climate-controlled respiration chambers for 8 d, where the air temperature was gradually increased from 7 to 21°C during the night and from 16 to 30°C during the day with daily increments of 2°C for both daytime and nighttime. During the 8-d data collection period, HR and gaseous exchange measurements were performed, and animal posture and activity were recorded continuously. The oxygen pulse (O2P), which represents the amount of oxygen that is consumed by the cow per heartbeat, was calculated as the ratio between VO2 and HR. Results showed that heat production and VO2 were linearly and positively associated with HR, but this relationship largely varied between individual cows. Within the range tested, O2P was unaffected by temperature, but we detected a tendency for an interaction of O2P with the temperature range tested during the night versus during the day. This indicates that the effect of air temperature on O2P is nonlinear. Standing and eating slightly increased O2P (1.0 and 2.5%) compared with lying down and idling, respectively, whereas rumination increased O2P by 5.1% compared with idling. It was concluded that the potential bias introduced by these effects on the O2P for the application of the technique is limited. The energy cost of eating and ruminating over idling was 223 ± 11 and 45 ± 6 kJ/kg0.75 per day, respectively, whereas the energy cost of standing over lying down was 53 ± 6 kJ/kg0.75 per day. We concluded that O2P in dairy cows was slightly affected by both animal posture and activity, but remained unaffected by air temperature within 8 to 32°C. Nonlinearity of the relationship between the O2P and air temperature suggests that caution is required extrapolating O2P beyond the temperature range evaluated in our experiment.

Exertional dyspnea responses to the Dyspnea Challenge in heart failure: Comparison to chronic obstructive pulmonary disease

BackgroundIn heart failure (HF), exertional dyspnea is a common symptom, but validated field-based tests for its measurement are limited. The Dyspnea Challenge is a two-minute uphill treadmill walk designed to measure exertional dyspnea in cardiopulmonary disease. ObjectivesThe purpose of this study was to establish the test-retest reliability of the Dyspnea Challenge in HF and to compare the exercise responses to a group with chronic obstructive pulmonary disease (COPD). MethodsThe study was an experimental, single-blind, randomized, multi-site project that recruited individuals with HF (New York Heart Association I-III) and COPD (Global Initiative for Chronic Obstructive Lung Disease II-IV). Participants completed two visits. On the first visit, participants performed two six-minute walk tests (6MWT), followed by two to three Dyspnea Challenges to calculate treadmill speed and gradient. At Visit Two, participants performed two separate Dyspnea Challenges, with one including measures of pulmonary gas exchange and central hemodynamics. ResultsTwenty-one individuals with HF (10 female; 66±11years; ejection fraction:45.3 ± 6.1%; six-minute distance(6MWD) 520 ± 97 m), and 25 COPD (11 female; 68 ± 10 yr; forced expiratory volume in 1 s:47.6 ± 11.5%; 6MWD: 430 ± 101 m). Intraclass correlation coefficients demonstrated excellent test-retest reliability for HF (0.94, P<.01) and COPD (0.95, P<.01). While achieving similar end-exercise exertional dyspnea intensities (P=.60), the HF group walked at a higher average speed (4.2 ± 0.8 vs. 3.5 ± 0.8km·h−1) and gradient (10.3 ± 2.8 vs. 9.6 ± 2.8%) and a greater oxygen uptake (P<.01) and ventilation (P<.01) than those with COPD. While achieving similar cardiac outputs (P=.98), stroke volumes (P=.97), and heart rates (P=.83), those with HF displayed a larger arteriovenous oxygen difference (P<.01), while those with COPD exhibited greater decreases in inspiratory capacity (P=.03), arterial oxygen saturation (P=.02), and breathing reserve (P<.01). ConclusionsThe Dyspnea Challenge is a reliable test-retest measure of exertional dyspnea in HF. Typical to their pathologies, HF seemed limited by an inadequate modulation of cardiac output, while ventilatory constraints hampered those with COPD.

Do You Get What You Pay for? Evaluating the Reliability of an Inexpensive Portable Photosynthesis System in Measuring Gas Exchange in Rice (Oryza sativa L.) Leaves

The availability of commercially available portable photosynthesis systems has facilitated widespread photosynthetic research. Our study aimed to evaluate the reliability of a recently developed inexpensive portable photosynthesis system, Yaxin-1105, in measuring gas exchange in rice (Oryza sativa L.) leaves. Gas exchange parameters, including net photosynthetic rate (Anet), stomatal conductance (gs), intercellular CO2 concentration (Ci), and transpiration rate (E), were measured on 88 rice leaves across seven rice cultivars and three growth stages (panicle initiation, heading, and early ripening), using both Yaxin-1105 and LI-6400XT. There were significant difference between each gas exchange parameter at each growth stage measured by Yaxin-1105 and LI-6400XT, except Ci at the heading stage. Mean Anet, gs, and E measured by Yaxin-1105 were 26–66% lower than those measured by LI-6400XT at panicle initiation, heading, and early ripening stages. Mean Ci measured by Yaxin-1105 was 13–22% higher than that measured by LI-6400XT at panicle initiation and early ripening stages. The coefficients of determination between each gas exchange parameter measured by Yaxin-1105 and by LI-6400XT at panicle initiation, heading, and early ripening stages ranged from only 0.0007 to 0.1889. These results indicate that the Yaxin-1105 is not a reliable tool for measuring gas exchange in rice leaves.

Measurements of exercise gas exchange during quantitative stress echocardiography in patient with coronary micovascular disease: a case report

Measurements of exercise gas exchange during quantitative stress echocardiography in patient with coronary micovascular disease: a case report

Measurement of exercise gas exchange during quantitative stress echocardiography might improve differentiation of myocardial ischemia from fibrosis

Measurement of exercise gas exchange during quantitative stress echocardiography might improve differentiation of myocardial ischemia from fibrosis

Fuel Selection in Skeletal Muscle Exercising at Low Intensity; Reliance on Carbohydrate in Very Sedentary Individuals.

Background: Resting skeletal muscle in insulin resistance prefers to oxidize carbohydrate rather than lipid, exhibiting metabolic inflexibility. Although this is established in resting muscle, complexities involved in directly measuring fuel oxidation using indirect calorimetry across a muscle bed have limited studies of this phenomenon in working skeletal muscle. During mild exercise and at rest, whole-body indirect calorimetry imperfectly estimates muscle fuel oxidation. We provide evidence that a method termed "ΔRER" can reasonably estimate fuel oxidation in skeletal muscle activated by exercise. Methods: Completely sedentary volunteers (n = 20, age 31 ± 2 years, V̇O2peak 24.4 ± 1.5 mL O2 per min/kg) underwent glucose clamps to determine insulin sensitivity and graded exercise consisting of three periods of mild steady-state cycle ergometry (15, 30, 45 watts, or 10%, 20%, and 30% of maximum power) with measurements of whole-body gas exchange. ΔRER, the RER in working muscle, was calculated as (V̇CO2exercise -V̇CO2rest)/(V̇O2exercise - V̇O2rest), from which the fraction of fuel accounted for by lipid was estimated. Results: Lactate levels were low and stable during steady-state exercise. Muscle biopsies were used to estimate mitochondrial content. The rise of V̇O2 at onset of exercise followed a monoexponential function, with a time constant of 51 ± 7 sec, typical of skeletal muscle; the average O2 cost of work was about 12 mL O2/watt/min, representing a mechanical efficiency of about 24%. At work rates of 30 or 45 watts, active muscle relied predominantly on carbohydrate, independent of insulin sensitivity within this group of very sedentary volunteers. Conclusions: The fraction of muscle fuel oxidation from fat was predicted by power output (P < 0.001) and citrate synthase activity (P < 0.05), indicating that low mitochondrial content may be the main driver of fuel choice in sedentary people, independent of insulin sensitivity.

The Lognormal Lung: A new approach to quantifying lung inhomogeneity in COPD.

Early diagnosis and disease phenotyping in COPD are currently limited by the use of spirometry, which may remain normal despite significant small-airways disease and which may not fully capture a patient's underlying pathophysiology. In this study we explored the use of a new non-invasive technique that assesses gas-exchange inhomogeneity in patients with COPD of varying disease severity (according to GOLD Stage), compared with age-matched healthy controls. The technique, which combines highly accurate measurement of respiratory gas exchange using a bespoke molecular flow sensor and a mechanistic mathematical model of the lung, provides new indices of lung function: the parameters σCL, σCd, and σVD represent the standard deviations of distributions for alveolar compliance, anatomical deadspace and vascular conductance relative to lung volume, respectively. It also provides parameter estimates for total anatomical deadspace and functional residual capacity (FRC). We demonstrate that these parameters are robust and sensitive, and that they can distinguish between healthy individuals and those with mild-moderate COPD (stage 1-2), as well as distinguish between mild-moderate COPD (stage 1-2) and more severe (stage 3-4) COPD. In particular, σCL, a measure of unevenness in lung inflation/deflation, could represent a more sensitive non-invasive marker of early or mild COPD. In addition, by providing a multi-dimensional assessment of lung physiology, this technique may also give insight into the underlying pathophysiological phenotype for individual patients. These preliminary results warrant further investigation in larger clinical research studies, including interventional trials.

A methodological and clinical approach to measured energy expenditure in the critically ill pediatric patient

The metabolic response to injury and stress is characterized initially by a decreased energy expenditure (Ebb phase) followed by an increased metabolic expenditure (Flow phase). Indirect calorimetry is a methodology utilized to measure energy expenditure and substrate utilization by measuring gas exchange in exhaled air and urinary nitrogen. The use of indirect calorimetry in critically ill patients requires precise equipment to obtain accurate measurements. The most recent guidelines suggested that measured energy expenditure by indirect calorimetry be used to determine energy requirements. This article reviews the methodological and clinical use of indirect calorimetry in critically ill pediatric patients.

Technical advances for measurement of gas exchange at the whole plant level: Design solutions and prototype tests to carry out shoot and rootzone analyses in plants of different sizes

To measure gas exchange at the whole plant (WP) level, design solutions were provided and prototypes of gas-exchange systems (GESs) were tested to carry out shoot and rootzone analyses in plants of different sizes. A WP-GES for small herbaceous plants was tested on the ability to maximize the net assimilation rate of CO2 in lettuce plants grown either under blue-red light or upon full spectrum artificial light. A WP-GES for large woody plants was tested during an experiment describing the drought stress inhibition of grapevine transpiration and photosynthesis. Technical advances pointed to optimize: i) the choice of cuvette material and its technical configuration to allow hermetic isolation of the interface shoot-rootzone, to avoid contamination between the two compartments, and to allow climate control of both shoot and rootzone cuvettes, ii) accurate measurements of the mass air-flow entering both cuvettes, and iii) an adequate homogenization of the cuvette air volume for stable and accurate detection of CO2 and H2O concentration in cuvettes before and after CO2 and H2O contamination of the air volumes exerted by plant organs.

Changes in Cost of Locomotion Are Higher after Endurance Cycling Than Running When Matched for Intensity and Duration.

Cost of locomotion (C L ) has been shown to increase after endurance running and cycling bouts. The main purpose of this study was to compare, in the same participants, the effect of both modalities on C L when matched for relative intensity and duration. Seventeen recreational athletes performed two incremental tests in running and cycling to determine the first ventilatory threshold then two 3-h bouts of exercise at 105% of threshold, with gas exchange measurements taken for 10 min at the start, middle and end of the 3 h to calculate C L . Neuromuscular fatigue during isometric knee extensor contractions and force-velocity profile on a cycle ergometer were assessed before and immediately after the 3-h trials. C L significantly increased at mid (+3.7%, P = 0.006) and end (+7.4%, P < 0.001) of exercise for cycling compared with start, whereas it did not change with time for running. Cardio-respiratory and metabolic variables changed similarly for cycling and running, therefore not explaining the time-course differences in C L between modalities. Changes in C L during cycling correlated significantly with loss of maximal force extrapolated from the force-velocity profile ( r = 0.637, P = 0.006) and changes in cadence ( r = 0.784, P < 0.001). The type of locomotion influences the effects of exercise on energy cost because 3 h of exercise at the same relative intensity caused a significant increase of cycling C L , and no changes in running C L . The changes in C L in cycling are likely due, at least in part, to fatigue in the locomotor muscles.

Respiratory function and CT abnormalities among survivors of COVID-19 pneumonia: a nationwide follow-up study

IntroductionConsidering the pulmonary burden caused by acute COVID-19, questions remain of respiratory consequences after recovery. The aim of the study was to describe respiratory function of COVID-19 pneumonia survivors at...

Modulation of grape cuticular wax composition following multiple heatwaves influences grape transpiration

Heat stress events (heatwaves) significantly impair grapevine leaf and berry physiology. The prevalence and frequency of heatwaves are predicted to increase in the coming decades, even in moderate climates. Despite this, many facets of heatwave effects on grapevine physiology remain unstudied. In this work, we subjected potted Gewürztraminer grapevines to a single heatwave event at mid-ripening or a double heatwave event at both the onset of ripening and mid-ripening and compared them to respective untreated control vines. The recovery of leaf and grape physiology from both events were analyzed on the day following the event and at harvest maturity through measurements of leaf gas exchange and chlorophyll fluorescence, and grape size, total soluble solids, and cuticular wax composition. Both single heatwave (S-HW) and double heatwave ( D -HW) treatments reduced chlorophyll fluorescence ( Fv/Fm ) by 12.8 % and 6.1 % on the day following the heatwave, respectively. However, values recovered at harvest maturity only by S-HW. Photosynthetic rate (Pn) was not affected by treatments on the day following the heatwave, but was reduced in D -HW by 48 % at harvest maturity. Total soluble solids were also decreased only by D -HW at harvest maturity. Following the D -HW, total berry wax (by 11.8 %), as well as the total contents of triterpenoids (by 11.7 %) and aldehydes (by 14.3 %) were increased significantly at harvest maturity. Fruit cuticular transpiration was reduced by D -HW. Interestingly, this decrease in transpiration was correlated with an increase in the ratio between the two most abundant wax compounds, oleanolic acid and ursolic acid, which are both triterpenoids. This data corroborates to suggest that grapevines are resilient to a single but not a double heatwave event. Future work will further explore the effects of heatwave frequency and recovery on additional facets of leaf physiology and grape quality. • Grapevines were exposed to a single or double heatwave event during ripening. • The double heatwave reduced leaf chlorophyll fluorescence and berry soluble solids. • The double heatwave raised total wax and triterpenoid contents in berries at harvest. • The double heatwave increased the ratio of oleanolic to ursolic acid at harvest. • The oleanolic to ursolic acid ratio correlated with lower cuticular transpiration.

Effect of Maize–Legume Intercropping on Maize Physio-Agronomic Parameters and Beneficial Insect Abundance

In developing countries, intercropping is commonly used to boost land productivity and agricultural benefits. However, in the Yucatan region of Mexico, maize (Zea mays L.) yields remain low, despite consistent fertilizer and pesticide inputs in traditional intercropping systems. Furthermore, little is known about the photosynthetic mechanisms that occur when maize plants interact with legumes, and there is a lack of understanding of how intercropping systems affect other organisms in the system, such as beneficial and insect pest population dynamics. A field experiment was carried out on the Yucatan Peninsula in 2021 to assess the impact of maize–legume intercropping systems on maize yield, physiological characteristics as evaluated by gas exchange measurements, and the abundance of beneficial insects in traditional and novel maize intercropping systems. The experiment was carried out with a randomized complete block design with three replicates. Treatments included maize intercropped with a novel legume, crotalaria (Crotalaria juncea L.), maize intercropped with a traditional legume, cowpea (Vigna unguiculata (L.) Walp.), and sole maize as a control. Significant differences in plant height were shown at growth stages V12 (45 days after sowing) and VT (60 days after sowing). No differences were observed in stem diameter, leaf area index, or chlorophyll content. The maize/cowpea intercrop increased the photosynthesis rate by 12.9% and 9.84% in the maize/crotalaria and sole maize, respectively (p &lt; 0.001), and transpiration rate by 6.5% and 8.5% in the maize intercropped with crotalaria and sole maize treatments, respectively (p &lt; 0.001), of maize plants. No significant effects on stomatal conductance or water use efficiency were observed, but the carbon intercellular rate was reduced by 9.74% and 9.15 when compared to the maize/crotalaria and the sole maize treatments, respectively. Overall, intercropping treatments attracted more beneficial insects than sole maize. For predators, the families that stood out were Coccinelidae, Formicidae, Araneidae, Thomisidae, Syrphidae, Chrysomelidae, Oxypidae, Vespidae, Reduviidae, Carabidae, Asilidae, Salthicidae, Dolichopodidae, while among parasitoids, the most frequent families were Eurytomydae, Braconidae, Tachinidae, Pteromalidae, Scelionidae, and Figitidae. In comparison to the maize/cowpea and maize/crotalaria treatments, the sole maize treatment resulted in a grain yield increase of 24.5% and 32%, respectively. However, sole maize was not statistically different to that of maize/cowpea intercropping. In conclusion, our findings suggest that maize/cowpea intercropping could be a viable alternative to sole maize cropping systems for enhancing maize yield and the abundance of beneficial insects, without increasing interspecific competition with the maize crop. Therefore, the maize/cowpea intercropping system represents a sustainable planting alternative for promoting maize grain yield and also promoting edible legume production within the system. Furthermore, the outcomes of this study can serve as a theoretical framework for increasing maize–legume intercropping profitability under growing conditions on the Yucatan Peninsula.

Evaluation and clinical significance of gas exchange in patients with acute respiratory distress syndrome

Gas exchange abnormalities is the pathophysiology characteristic of acute respiratory distress syndrome (ARDS). The severity of gas exchange abnormalities not only reflect the severity and outcome of the disease, but could also be an important index to guide individual mechanical ventilation settings and evaluate the therapeutic effects of inhaled vasodilator. The common techniques to measure gas exchange include multiple inert gas elimination technique, automatic lung parameter estimator, electrical impedance tomography, and single-photon emission CT. Nowadays, bedside techniques and measurements for improving gas exchange function in ARDS patients are still limited. Therefore, the improvement and promotion of bedside real-time gas exchange monitoring technology may achieve the goal of personalized medicine in ARDS. This article reviewed the common evaluation methods of gas exchange function in ARDS and their significance, in order to pay more attention to the evaluation of gas exchange function and further improve the prognosis of patients with ARDS.