Ulmus crassifolia Nutt. (Cedar elm, Ulmaceae) is a tree found in central and east Texas, northern Mexico, east to Florida, and north to southern Missouri and Oklahoma. Ungnadia speciosa Endl. (Mexican-buckeye, Sapinda...Ulmus crassifolia Nutt. (Cedar elm, Ulmaceae) is a tree found in central and east Texas, northern Mexico, east to Florida, and north to southern Missouri and Oklahoma. Ungnadia speciosa Endl. (Mexican-buckeye, Sapindaceae) is a shrub or small tree found in woodlands and savannas of central and western Texas, southern New Mexico and northern Mexico. In central Texas, both species are found in Juniperus ashei/Quercus virginiana woodlands or savannas or also at low density in inter-canopy grassland gaps or patches. Environmental conditions in this area are stressful because of shallow soils, high summer temperatures, and inconsistent low rainfall. Currently, both species have a low density in these areas, and Ulmus crassifolia is usually a tree, while Ungnadia speciosa is a woody understory shrub. This study suggests U. crassifolia and U. speciosa are tolerant or intermediate species, with juveniles starting in shade. Maximum photosynthetic rate (A<sub>max</sub>), dark respiration (R<sub>d</sub>), intercellular CO<sub>2</sub>, light saturation (L<sub>sp</sub>) and water use efficiency significantly increased when light levels and CO<sub>2</sub> concentrations were elevated for both species, but not when temperatures were elevated. Stomatal conductance decreased when the CO<sub>2</sub> concentration doubled, but there were few effects from elevated temperature. These findings suggest that U. speciosa and U. crassifolia should be more common and imply that they will have a higher density in a future high CO<sub>2</sub> environment.展开更多
On the sunny days, there were little diurnal changes in both azimuth and directional angle for either sun_ or shade_leaflet. However, there existed a significant diurnal change in midrib angle that reflected movements...On the sunny days, there were little diurnal changes in both azimuth and directional angle for either sun_ or shade_leaflet. However, there existed a significant diurnal change in midrib angle that reflected movements regarding evasion of light stress around noon hours. On the cloudy day, a very little diurnal difference was found in azimuth, directional and midrib angle. It is suggested that changing light environment is the main factor for inducing leaflet movement of Robinia pseudoacacia , and the rhythmical movement does not attribute to the leaflet movement. Leaf orientation control test showed that the photosynthetic rate ( Pn ), stomatal conductance ( g s ) and transpiration ( Tr ) of the artificial fixed_leaflets were significantly lower than that of control_leaflets. And the leaf temperature ( Tl ) of the fixed leaflets significantly exceeded that of control_leaflets, which may attribute to the significant difference of light interception between the fixed and control_leaflets. The light_dependent leaflet movement is the morphological adjustment of maintaining optimal physiological status.展开更多
A model for modified-atmosphere packaging （MAP） systems containing fruits and vegetables was developed.The computer simulation was performed to predict the gas mass concentrations inside the packages and was success...A model for modified-atmosphere packaging （MAP） systems containing fruits and vegetables was developed.The computer simulation was performed to predict the gas mass concentrations inside the packages and was successfully verified by experiments with yellow peaches at 5,15 and 25 ℃ using two types of packaging films.A Michaelis-Menten type respiration model with noncompetitive inhibition mechanism due to CO2 was adopted while the respiration rates were measured with an improved permeable system method suitable for either steady or unsteady state.The applicability of the model in the design of MAP systems was demonstrated with a calculation to evaluate film specification and equilibrium concentrations of O2 and CO2 in the package containing yellow peaches.展开更多
Naked oat（Avena nuda L.） was originated from China,where soil nitrogen（N） is low availability.The responses of chlorophyll（Chl.） fluorescence parameters and leaf gas exchange to N application were analysed in th...Naked oat（Avena nuda L.） was originated from China,where soil nitrogen（N） is low availability.The responses of chlorophyll（Chl.） fluorescence parameters and leaf gas exchange to N application were analysed in this study.After the N application rate ranged from 60 to 120 kg ha-1,variable fluorescence（F v）,the maximal fluorescence（F m）,the maximal photochemical efficiency（F v /F m）,quantum yield（Φ PS II） of the photosynthetic system II（PS II）,electron transport rate（ETR）,and photochemical quenching coefficient（qP） increased with N application level,however,non-photochemical quenching coefficient（qN） decreased.Moreover,there was no difference in initial fluorescence（F o） with further more N enhancement.The maximum net photosynthetic rate（P max）,apparent dark respiration rate（R d） and light saturation point（LSP） were improved with 40-56 kg N ha-1as basal fertilizer and 24-40 kg N ha-1as top dressing fertilizer applied at jointing stage.Initial quantum yield（α） was decreased with 24 kg N ha-1as basal fertilizer and 56 kg N ha-1as top dressing fertilizer.Flag-leaf net photosynthetic rate（P n） was significantly enhanced at the jointing and heading stages with 40-56 kg N ha-1as basal fertilizer; in addition,increased at grain filling stage of naked oat with 40-56 kg N ha-1as top dressing fertilizer.90 kg N ha-1（50-70% as basal fertilizer and 30-50% as top dressing fertilizer） application is recommended to alleviate photodamage of photosystem and improve the photosynthetic rate in naked oat.展开更多
AIM: To assess the impact of transjugular intrahepatic portosystemic shunt (TIPS) on pulmonary gas exchange and to evaluate the use of TIPS for the treatment of hepatopulmonary syndrome (HPS).METHODS: Seven patients, ...AIM: To assess the impact of transjugular intrahepatic portosystemic shunt (TIPS) on pulmonary gas exchange and to evaluate the use of TIPS for the treatment of hepatopulmonary syndrome (HPS).METHODS: Seven patients, three of them with advanced HPS, in whom detailed pulmonary function tests were performed before and after TIPS placementat the University of Alabama Hospital and at the Hospital Clinic, Barcelona, were considered.RESULTS: TIPS patency was confirmed by hemodynamic evaluation. No changes in arterial blood gases were observed in the overall subset of patients. Transient arterial oxygenation improvement was observed in only one HPS patient, early after TIPS, but this was not sustained 4 mo later.CONCLUSION: TIPS neither improved nor worsened pulmonary gas exchange in patients with portal hypertension. This data does not support the use of TIPS as a specific treatment for HPS. However, it does reinforce the view that TIPS can be safely performed for the treatment of other complications of portal hypertension in patients with HPS.展开更多
To clarify the changes in plant photosynthesis and mechanisms underlying those responses to gradually increasing soil drought stress and reveal quantitative relationships between photosynthesis and soil moisture,soil ...To clarify the changes in plant photosynthesis and mechanisms underlying those responses to gradually increasing soil drought stress and reveal quantitative relationships between photosynthesis and soil moisture,soil water conditions were controlled in greenhouse pot experiments using 2-year-old seedlings of Forsythia suspensa（Thunb.） Vahl. Photosynthetic gas exchange and chlorophyll fluorescence variables were measured and analyzed under 13 gradients of soil water content. Net photosynthetic rate（PN）, stomatal conductance（gs）, and water-use efficiency（WUE） in the seedlings exhibited a clear threshold response to the relative soil water content（RSWC）. The highest PNand WUEoccurred at RSWCof51.84 and 64.10%, respectively. Both PNand WUEwere higher than the average levels at 39.79% B RSWCB 73.04%. When RSWCdecreased from 51.84 to 37.52%,PN, gs, and the intercellular CO2 concentration（Ci）markedly decreased with increasing drought stress; the corresponding stomatal limitation（Ls） substantially increased, and nonphotochemical quenching（NPQ） also tended to increase, indicating that within this range of soil water content, excessive excitation energy was dispersed from photosystem II（PSII） in the form of heat, and the reduction in PNwas primarily due to stomatal limitation.While RSWCdecreased below 37.52%, there were significant decreases in the maximal quantum yield of PSII photochemistry（Fv/Fm） and the effective quantum yield of PSII photochemistry（UPSII）, photochemical quenching（qP）, and NPQ; in contrast, minimal fluorescence yield of the dark-adapted state（F0） increased markedly. Thus,the major limiting factor for the PNreduction changed to a nonstomatal limitation due to PSII damage. Therefore, an RSWCof 37.52% is the maximum allowable water deficit for the normal growth of seedlings of F. suspensa, and a water content lower than this level should be avoided in field soil water management. Water contents should be maintained in the range of 39.79% B RSWCB 73.04% to ensure normal function of the photosynthetic apparatus and high levels of photosynthesis and efficiency in F.suspensa.展开更多
Effect of different shading levels (no-shading, 80% shading, and 40% shading) on photosynthetic and stomatal responses in cotton leaves were investigated under conditions of different soil water contents in summer mid...Effect of different shading levels (no-shading, 80% shading, and 40% shading) on photosynthetic and stomatal responses in cotton leaves were investigated under conditions of different soil water contents in summer midday. All cotton leaves exhibited similar basic responses to shading, including decreased net photosynthetic rates, a tendency to decrease in transpiration rates, and increased stomatal conductance and intercellular CO2 concentration. The leaf conductance of 80% shaded and 40% shaded plants increased by 28% and 16.7% compared with no-shaded plants at high water, respectively, but the net photosynthetic rates of 80% shaded and 40% shaded plants declined by 50% and 14.73%, respectively. Results showed that combined effect of soil moisture and shading on photosynthetic and stomatal responses in cotton leaves was very remarkable.展开更多
Rhodiola sachalinensis growing in the different habitats, Xiaotianchi plot (altitude 1800 m), Tree line plot (altitude 2000 m) and Tianwenfeng plot (altitude 2325 m), of Changbai Moutain (northern slop) were transplan...Rhodiola sachalinensis growing in the different habitats, Xiaotianchi plot (altitude 1800 m), Tree line plot (altitude 2000 m) and Tianwenfeng plot (altitude 2325 m), of Changbai Moutain (northern slop) were transplanted to Harbin Experimental Forest Farm for measuring its characteristic of gas exchange. The study results indicated that the growth state and gas exchange characteristics ofRh. sachalinensis growing in different habitats varied markedly. The plants transplanted from Tianwenfeng plot had the highest values in net photosynthesis rate (Pn) and transpiration rate (Tr), those transplanted from Tree line plot shows the second, and those transplanted rom Xiaotianchi plot had the lowest values. The variance existed in transplanted plants was the same as shown in the field. From the result it can be extrapolated that the difference of Pn and Tr existed inRh. sachalinensis transplanted from different habitats is depend not only on the environmental factors, but on the variance of physiological characteristic of plant itself.展开更多
Rhodiola sachalinensis growing in the different habitats, such as Xiaotianchi plot (altitude 1800 m), Tree line plot (altitude 2000 m) and Tianwenfeng plot (altitude 2325 m) of Changbai Mountain (northern slop) were t...Rhodiola sachalinensis growing in the different habitats, such as Xiaotianchi plot (altitude 1800 m), Tree line plot (altitude 2000 m) and Tianwenfeng plot (altitude 2325 m) of Changbai Mountain (northern slop) were transplanted to Harbin Experimental Farm for determining its gas exchange. The study results indicated that the diurnal changes of gas exchange ofRh. sachalinensis transplanted from different habitats were still different though the morphological appearance of the newly sprouted above-ground part had become more similar. For net photosynthesis rate (Pn), stomatal conductance (Gs) and apparent quantum yield (AQY), the diumal change curves ofRh. sachalinensis transplanted from the three plots were similar, but the data value were different. For the dark respiration rate (Rd), transpiration rate (Tr) and water use efficiency (WUE), diurnal change curves of the three plots were obviously different.展开更多
Three-dimensional transient numerical simulation of gas exchange process in a four-stroke motorcycle engine with a semi-spherical combustion chamber with two tilt valves was studied. Combination of the grid re-meshing...Three-dimensional transient numerical simulation of gas exchange process in a four-stroke motorcycle engine with a semi-spherical combustion chamber with two tilt valves was studied. Combination of the grid re-meshing method and the snapper technique made the valves move smoothly. The flow structure and pattern in a complete engine cycle were described in detail. Tumble ratios around the x-axis and y-axis were analyzed. Comparison of computed pressure with experimental pressure under motored condition revealed that the simulation had high calculation precision; CFD simulation can be regarded as an im-portant tool for resolving the complex aerodynamic behavior in motorcycle engines.展开更多
The in-cylinder gas exchange process is crucial to the power performance of two-stroke aircraft piston engines,which is easily influenced by complex factors such as high-altitude performance variation and in-cylinder ...The in-cylinder gas exchange process is crucial to the power performance of two-stroke aircraft piston engines,which is easily influenced by complex factors such as high-altitude performance variation and in-cylinder flow characteristics.This paper reviews the development history and characteristics of gas exchange types,as well as the current state of theory and the validation methods of gas exchange technology,while also discusses the trends of cutting-edge technologies in the field.This paper provides a theoretical foundation for the optimization and engineering design of gas exchange systems and,more importantly,points out that the innovation of gas exchange types,the modification of theoretical models,and the technology of variable airflow organization are the key future research directions in this field.展开更多
The poppet valves two-stroke(PV2S)aircraft engine fueled with sustainable aviation fuel is a promising option for general aviation and unmanned aerial vehicle propulsion due to its high power-to-weight ratio,uniform t...The poppet valves two-stroke(PV2S)aircraft engine fueled with sustainable aviation fuel is a promising option for general aviation and unmanned aerial vehicle propulsion due to its high power-to-weight ratio,uniform torque output,and flexible valve timings.However,its high-altitude gas exchange performance remains unexplored,presenting new opportunities for optimization through artificial intelligence(AI)technology.This study uses validated 1D+3D models to evaluate the high-altitude gas exchange performance of PV2S aircraft engines.The valve timings of the PV2S engine exhibit considerable flexibility,thus the Latin hypercube design of experiments(DoE)methodology is employed to fit a response surface model.A genetic algorithm(GA)is applied to iteratively optimize valve timings for varying altitudes.The optimization process reveals that increasing the intake duration while decreasing the exhaust duration and valve overlap angles can significantly enhance high-altitude gas exchange performance.The optimal valve overlap angle emerged as 93°CA at sea level and 82°CA at 4000 m altitude.The effects of operating parameters,including engine speed,load,and exhaust back pressure,on the gas exchange process at varying altitudes are further investigated.The higher engine speed increases trapping efficiency but decreases the delivery ratio and charging efficiency at various altitudes.This effect is especially pronounced at elevated altitudes.The increase in exhaust back pressure will significantly reduce the delivery ratio and increase the trapping efficiency.This study demonstrates that integrating DoE with AI algorithms can enhance the high-altitude performance of aircraft engines,serving as a valuable reference for further optimization efforts.展开更多
The high frequency ventilation(HFV)can well support the breathing of respiratory patient with 20%-40%of normal tidal volume.Now as a therapy of rescue ventilation when conversional ventilation failed,the HFV has been ...The high frequency ventilation(HFV)can well support the breathing of respiratory patient with 20%-40%of normal tidal volume.Now as a therapy of rescue ventilation when conversional ventilation failed,the HFV has been applied in the treatments of severe patients with acute respiratory failure(ARF),acute respiratory distress syndrome(ARDS),etc.However,the gas exchange mechanism(GEM)of HFV is still not fully understood by researchers.In this paper,the GEM of HFV is reviewed to track the studies in the last decades and prospect for the next likely studies.And inspired by previous studies,the GEM of HFV is suggested to be continually developed with various hypotheses which will be testified in simulation,experiment and clinic trail.One of the significant measures is to study the GEM of HFV under the cross-disciplinary integration of medicine and engineering.Fully understanding the GEM can theoretically support and expand the applications of HFV,and is helpful in investigating the potential indications and contraindications of HFV.展开更多
The article focuses on a theoretical and experimental framework for the quantification of interaction between nonlinear geomechnical and physicochemical processes in high-stress coal-bearing rock mass during mining un...The article focuses on a theoretical and experimental framework for the quantification of interaction between nonlinear geomechnical and physicochemical processes in high-stress coal-bearing rock mass during mining under high seismic risk due to large-scale blasting and earthquakes,as well as because of structural and temperature effects.The tests were aimed to examine and study comprehensively the piston mechanism of gas exchange and mass transfer processes,revealed recently at the Institute of Mining,SB RAS,as well as to explain the fact that the earthquake-induced low-velocity(quasi-meter range)pendulum waves(velocity to 1 m/s and frequency of 0.5–5 Hz)could stimulate an increase in the gas content in coal mines.In order to perform laboratory investigation at the Institute of Mining SB RAS,special-purpose stand for analyzing gas exchange and mass transfer processes in coal-bearing geomaterials under various thermodynamic conditions(P,V,T)and gas composition was constructed in cooperation with the Institute of Semiconductors Physics SB RAS.Matching of air flow rate with compression pressures allowed to obtain relations showing that air flow rate increases at the uncertain time interval under the increasing of the compression pressure.The same measurements was carried out with another gases such as Hydrogen H_(2),Helium He,methane CH_(4),carbon dioxide CO_(2) and carbon oxide CO.The laboratory tests aimed to detailed investigation of the previously revealed“piston mechanism”of gas exchange and mass transfer processes in the coal specimens and their quantitative description in terms of theory of the pendulum waves were carried in the first time.Consequently,there are some arguments for the testing of the opportunity of quantitative description of the“piston mechanism”related to gas exchange and mass transfer processes in the scale of coal mines.It is relevant when pendulum waves induced by powerful earthquakes and technical blasting reaches the mine.展开更多
1.Challenges circular methane energy systems In recent decades,methane-based energy systems have rapidly gained traction across the globe because of the increasing availability of low-cost methane production capacity....1.Challenges circular methane energy systems In recent decades,methane-based energy systems have rapidly gained traction across the globe because of the increasing availability of low-cost methane production capacity.However,fossil methane production and combustion lead to large greenhouse gas emissions,contributing to climate change[1].展开更多
Objective： To compare the effect between nebulized and intravenous administration of Shenmai Injection （参麦注射液） on pulmonary gas exchange function of patients following tourniquet-induced lower limb ischemia-re...Objective： To compare the effect between nebulized and intravenous administration of Shenmai Injection （参麦注射液） on pulmonary gas exchange function of patients following tourniquet-induced lower limb ischemia-repeffusion. Methods： Thirty-eight patients scheduled for lower extremity surgery were randomized into three groups using the closed envelop method： Shenmai Injection was administered 30 min before tourniquet inflation by nebulization [0.6 mL/kg in 10 mL normal saline （NS）] in the nebulization group or by intravenous drip （0.6 mL/kg dissolved in 250 mL of 10% glucose） in the intravenous drip group, and equal volume of NS was given intravenously in the NS group; 15 in each group. Arterial blood gases were analyzed, serum levels of malonaldehyde （MDA） and interleukine-6 （IL-6） and interleukine-8 （IL-8） were determined using the method of thiobarbituric acid reaction and enzyme-linked immuno sorbent assay respectively just before tourniquet inflation （TO）, and at 0.5 h （T1）, 2 h （TZ）, 6 h （T3） after tourniquet deflation. Results： Compared with baselines at TO, MDA levels significantly increased at TZ, T3 in the NS group and at T3 in the nebulization group, and IL-6 and IL-8 levels were significantly increased at TZ, T3 in NS, the intravenous drip and the nebulization groups （P〈0.05）. Arterial pressure of oxygen （PaO2） at T3 was decreased, while alveolar- arterial oxygen tension showed difference （PA-aDO2） at T3 in the NS group; RI at T3 in both intravenous drip and the nebulization groups were enhanced （P〈0.05）. Compared with the NS group, MDA and IL-8 levels at TZ, T3, 11-6 at T3 in the intravenous drip group, and IL-8 at T3 in the nebulization group were all remarkably increased （P〈0.05）. Additionally, MDA level at T3 in the nebulization group was higher than that in the intravenous drip group （P〈0.05）. Conclusions： Intravenous administration of Shenmai Injection provided a better protective effect than nebulization in mitigating pulmonary gas exchange dysfunction in patients following tourniquet-induced limb ischemia-repertusion.展开更多
Chlorophyll and anthocyanin contents provide a valuable indicator of the status of a plant’s physiology, but to be more widely utilized it needs to be assessed easily and non‐destructively. This is particularly evid...Chlorophyll and anthocyanin contents provide a valuable indicator of the status of a plant’s physiology, but to be more widely utilized it needs to be assessed easily and non‐destructively. This is particularly evident in terms of assessing and exploiting germplasm for plant‐breeding programs. We report, for the first time, experiments with Fragaria chiloensis（L.）Duch. and the estimation of the effects of response to salinity stress（0, 30, and 60 mmol NaCl/L） in terms of these pigments content and gas exchange. It is shown that both pigments（which interestingly, themselves show a high correlation） give a good indication of stress response. Both pigments can be accurately predicted using spectral reflectance indices（SRI）;however, the accuracy of the predictions was slightly improved using multilinear regression analysis models and genetic algorithm analysis. Specifically for chlorophyll content, unlike other species, the use of published SRI gave better indications ofstress response than Normalized Difference Vegetation Index.The effect of salt on gas exchange is only evident at the highest concentration and some SRI gave better prediction performance than the known Photochemical Reflectance Index. This information will therefore be useful for identifying tolerant genotypes to salt stress for incorporation in breeding programs.展开更多
In the present study, we Investigated the effects of Increaslng sallnlty on growth, gas exchange, absclslc acld （ABA）, calmodulln （CAM）, and the relevance to salt tolerance In seedllngs of Populus euphratlca Ollv....In the present study, we Investigated the effects of Increaslng sallnlty on growth, gas exchange, absclslc acld （ABA）, calmodulln （CAM）, and the relevance to salt tolerance In seedllngs of Populus euphratlca Ollv. and cutUngs of P. ＂pupularls 35-44＂ （P. popularls） and P. x euramerlcana cv. 1-214 （P. cv. Itallca）. The relatlve growth rates of shoot helght （RGR,） for P. cv. Itallca and P. popularls were severely reduced by Increaslng salt stress, whereas the growth reductlon was relatlvely less in P. euphratica. Slmllarly, P. euphratlca malntalned hlgher net photosynthetlc rates （Pn） and unlt transplration rotes （TRN） than P. cv. Itallca and P. popularls under condltlons of hlgher sallnlty. Sallnity caused a slgnlficant increase In leaf ABA and CaM In the three genotypes after the onset of stress, but NaCl-induced ABA and CaM accumulatlon was more pronounced In P. euphratlca, suggeeUng that P. euphratlca plants are more sensitlve in sensing soil salinlty than the other two poplars. Furthermore, P. euphratica maintained relatively higher ABA and CaM concentrations under conditions of high salinity. The higher capacity to synthesize stress signals, namely ABA and CaM, In P. euphratica and the contrlbuUon of this to the salt resistance of P. euphratica are discussed.展开更多
Aims Climate change largely impacts ecosystem carbon and water cycles by changing plant gas exchange,which may further cause positive or negative feedback to global climate change.However,long-term global change manip...Aims Climate change largely impacts ecosystem carbon and water cycles by changing plant gas exchange,which may further cause positive or negative feedback to global climate change.However,long-term global change manipulative experiments are seldom conducted to reveal plant ecophysiological responses to climatic warming and altered precipitation regimes.Methods An 8-year field experiment with both warming and increased precipitation was conducted in a temperate grassland in northern China.We measured leaf gas exchange rates(including plant photosynthesis,transpiration and instantaneous water use efficiency[WUE])of two dominant plant species(Stipa sareptana var.krylovii and Agropyron cristatum)from 2005 to 2012(except 2006 and 2010)and those of other six species from 2011 to 2012.Important Findings Increased precipitation significantly stimulated plant photosynthetic rates(A)by 29.5%and 19.9%and transpiration rates(E)by 42.2%and 51.2%for both dominant species S.sareptana var.krylovii and A.cristatum,respectively,across the 8 years.Similarly,A and E of the six plant functional types were all stimulated by increased precipitation in 2011 and 2012.As the balance of A and E,the instantaneous WUEs of different plant species had species-specific responses to increased precipitation.In contrast,neither warming nor its interaction with increased precipitation significantly affected plant leaf gas exchange rates.Furthermore,A and E of the two dominant species and their response magnitudes to water treatments positively correlated with rainfall amount in July across years.We did not find any significant difference between the short-term versus long-term responses of plant photosynthesis,suggesting the flexibility of leaf gas exchange under climate change.The results suggest that changing precipitation rather than global warming plays a prominent role in determining production of this grassland in the context of climate change.展开更多
Aims Drought stress and the degree of drought severity are predicted to rise under highly variable patterns of precipitation due to climate change,while the capacity of trees to cope with drought recovery through phys...Aims Drought stress and the degree of drought severity are predicted to rise under highly variable patterns of precipitation due to climate change,while the capacity of trees to cope with drought recovery through physiological and biochemical adjustment remains unclear.We aimed to examine the coupling of physiology and biochemistry in trees during drought and the following recovery.Methods Potted seedlings of Cinnamomum camphora were grown under well watered conditions prior to the experimental drought stress,which was initiated by withholding water.Seedlings were rewatered following attainment of two drought severities:mild drought(stomatal closure)and moderate drought(ψxylem=−1.5 MPa).We measured leaf-level water potential,gas exchange(photosynthesis and stomatal conductance),abscisic acid(ABA),proline and non-structural carbohydrates(NSCs)concentrations in seedlings of C.camphora during drought and a 4-day recovery.Important Findings We found that drought severity largely determined physiological and biochemical responses and affected the rate of recovery.Stomatal closure occurred at the mild drought stress,accompanied with ABA accumulation in leaves and decline in water potential,while leaf proline accumulation and variable NSC were evident at the moderate drought stress.More severe drought stress led to delayed recovery of gas exchange,but it did not have significant effect on water potential recovery.The relationships of water potential and gas exchange differed during drought stress and post-drought recovery.There was tight coupling between water potential and gas exchange during drought,but not during rewatering due to high ABA accumulation in leaves,thereby delaying recovery of stomatal conductance.Our results demonstrate that ABA could be an important factor in delaying the recovery of stomatal conductance following rewatering and after water potential recovery of C.camphora.Furthermore,greater drought severity had significant impacts on the rate of recovery of tree physiology and biochemistry.展开更多
文摘Ulmus crassifolia Nutt. (Cedar elm, Ulmaceae) is a tree found in central and east Texas, northern Mexico, east to Florida, and north to southern Missouri and Oklahoma. Ungnadia speciosa Endl. (Mexican-buckeye, Sapindaceae) is a shrub or small tree found in woodlands and savannas of central and western Texas, southern New Mexico and northern Mexico. In central Texas, both species are found in Juniperus ashei/Quercus virginiana woodlands or savannas or also at low density in inter-canopy grassland gaps or patches. Environmental conditions in this area are stressful because of shallow soils, high summer temperatures, and inconsistent low rainfall. Currently, both species have a low density in these areas, and Ulmus crassifolia is usually a tree, while Ungnadia speciosa is a woody understory shrub. This study suggests U. crassifolia and U. speciosa are tolerant or intermediate species, with juveniles starting in shade. Maximum photosynthetic rate (A<sub>max</sub>), dark respiration (R<sub>d</sub>), intercellular CO<sub>2</sub>, light saturation (L<sub>sp</sub>) and water use efficiency significantly increased when light levels and CO<sub>2</sub> concentrations were elevated for both species, but not when temperatures were elevated. Stomatal conductance decreased when the CO<sub>2</sub> concentration doubled, but there were few effects from elevated temperature. These findings suggest that U. speciosa and U. crassifolia should be more common and imply that they will have a higher density in a future high CO<sub>2</sub> environment.
文摘On the sunny days, there were little diurnal changes in both azimuth and directional angle for either sun_ or shade_leaflet. However, there existed a significant diurnal change in midrib angle that reflected movements regarding evasion of light stress around noon hours. On the cloudy day, a very little diurnal difference was found in azimuth, directional and midrib angle. It is suggested that changing light environment is the main factor for inducing leaflet movement of Robinia pseudoacacia , and the rhythmical movement does not attribute to the leaflet movement. Leaf orientation control test showed that the photosynthetic rate ( Pn ), stomatal conductance ( g s ) and transpiration ( Tr ) of the artificial fixed_leaflets were significantly lower than that of control_leaflets. And the leaf temperature ( Tl ) of the fixed leaflets significantly exceeded that of control_leaflets, which may attribute to the significant difference of light interception between the fixed and control_leaflets. The light_dependent leaflet movement is the morphological adjustment of maintaining optimal physiological status.
基金The Start-up Research Fund for Teachers withDoctor s Degree by Shanghai University of Science and Technology (No.X530)the Key Subject Foundation of Shanghai Education Committee(PeriodⅣ).
文摘A model for modified-atmosphere packaging （MAP） systems containing fruits and vegetables was developed.The computer simulation was performed to predict the gas mass concentrations inside the packages and was successfully verified by experiments with yellow peaches at 5,15 and 25 ℃ using two types of packaging films.A Michaelis-Menten type respiration model with noncompetitive inhibition mechanism due to CO2 was adopted while the respiration rates were measured with an improved permeable system method suitable for either steady or unsteady state.The applicability of the model in the design of MAP systems was demonstrated with a calculation to evaluate film specification and equilibrium concentrations of O2 and CO2 in the package containing yellow peaches.
基金the study grants from the Special Fund for Agro-Scientific Research in the Public Interest,China(nyhyzx07-009-2)the Earmarked Fund for China Agriculture Research System(CARS-08-B-1)
文摘Naked oat（Avena nuda L.） was originated from China,where soil nitrogen（N） is low availability.The responses of chlorophyll（Chl.） fluorescence parameters and leaf gas exchange to N application were analysed in this study.After the N application rate ranged from 60 to 120 kg ha-1,variable fluorescence（F v）,the maximal fluorescence（F m）,the maximal photochemical efficiency（F v /F m）,quantum yield（Φ PS II） of the photosynthetic system II（PS II）,electron transport rate（ETR）,and photochemical quenching coefficient（qP） increased with N application level,however,non-photochemical quenching coefficient（qN） decreased.Moreover,there was no difference in initial fluorescence（F o） with further more N enhancement.The maximum net photosynthetic rate（P max）,apparent dark respiration rate（R d） and light saturation point（LSP） were improved with 40-56 kg N ha-1as basal fertilizer and 24-40 kg N ha-1as top dressing fertilizer applied at jointing stage.Initial quantum yield（α） was decreased with 24 kg N ha-1as basal fertilizer and 56 kg N ha-1as top dressing fertilizer.Flag-leaf net photosynthetic rate（P n） was significantly enhanced at the jointing and heading stages with 40-56 kg N ha-1as basal fertilizer; in addition,increased at grain filling stage of naked oat with 40-56 kg N ha-1as top dressing fertilizer.90 kg N ha-1（50-70% as basal fertilizer and 30-50% as top dressing fertilizer） application is recommended to alleviate photodamage of photosystem and improve the photosynthetic rate in naked oat.
基金Supported by FIS 02/0692 and 02/0739 from the Fondo de In-vestigaciones Sanitarias, SGR 2001 SGR00286 from the Gener-alitat de Catalunya (DURSI), and CO 3/02 and CO 3/11 from the Instituto de Salud Carlos Ⅲ
文摘AIM: To assess the impact of transjugular intrahepatic portosystemic shunt (TIPS) on pulmonary gas exchange and to evaluate the use of TIPS for the treatment of hepatopulmonary syndrome (HPS).METHODS: Seven patients, three of them with advanced HPS, in whom detailed pulmonary function tests were performed before and after TIPS placementat the University of Alabama Hospital and at the Hospital Clinic, Barcelona, were considered.RESULTS: TIPS patency was confirmed by hemodynamic evaluation. No changes in arterial blood gases were observed in the overall subset of patients. Transient arterial oxygenation improvement was observed in only one HPS patient, early after TIPS, but this was not sustained 4 mo later.CONCLUSION: TIPS neither improved nor worsened pulmonary gas exchange in patients with portal hypertension. This data does not support the use of TIPS as a specific treatment for HPS. However, it does reinforce the view that TIPS can be safely performed for the treatment of other complications of portal hypertension in patients with HPS.
基金supported by the National Natural Science Foundation of China(Nos.41621061,31500511)the Natural Science Foundation of Shandong Province of China(No.ZR2015CL044)
文摘To clarify the changes in plant photosynthesis and mechanisms underlying those responses to gradually increasing soil drought stress and reveal quantitative relationships between photosynthesis and soil moisture,soil water conditions were controlled in greenhouse pot experiments using 2-year-old seedlings of Forsythia suspensa（Thunb.） Vahl. Photosynthetic gas exchange and chlorophyll fluorescence variables were measured and analyzed under 13 gradients of soil water content. Net photosynthetic rate（PN）, stomatal conductance（gs）, and water-use efficiency（WUE） in the seedlings exhibited a clear threshold response to the relative soil water content（RSWC）. The highest PNand WUEoccurred at RSWCof51.84 and 64.10%, respectively. Both PNand WUEwere higher than the average levels at 39.79% B RSWCB 73.04%. When RSWCdecreased from 51.84 to 37.52%,PN, gs, and the intercellular CO2 concentration（Ci）markedly decreased with increasing drought stress; the corresponding stomatal limitation（Ls） substantially increased, and nonphotochemical quenching（NPQ） also tended to increase, indicating that within this range of soil water content, excessive excitation energy was dispersed from photosystem II（PSII） in the form of heat, and the reduction in PNwas primarily due to stomatal limitation.While RSWCdecreased below 37.52%, there were significant decreases in the maximal quantum yield of PSII photochemistry（Fv/Fm） and the effective quantum yield of PSII photochemistry（UPSII）, photochemical quenching（qP）, and NPQ; in contrast, minimal fluorescence yield of the dark-adapted state（F0） increased markedly. Thus,the major limiting factor for the PNreduction changed to a nonstomatal limitation due to PSII damage. Therefore, an RSWCof 37.52% is the maximum allowable water deficit for the normal growth of seedlings of F. suspensa, and a water content lower than this level should be avoided in field soil water management. Water contents should be maintained in the range of 39.79% B RSWCB 73.04% to ensure normal function of the photosynthetic apparatus and high levels of photosynthesis and efficiency in F.suspensa.
基金Project (No. 49725102) supported by the National Outstanding Youth Science Foundation of China.
文摘Effect of different shading levels (no-shading, 80% shading, and 40% shading) on photosynthetic and stomatal responses in cotton leaves were investigated under conditions of different soil water contents in summer midday. All cotton leaves exhibited similar basic responses to shading, including decreased net photosynthetic rates, a tendency to decrease in transpiration rates, and increased stomatal conductance and intercellular CO2 concentration. The leaf conductance of 80% shaded and 40% shaded plants increased by 28% and 16.7% compared with no-shaded plants at high water, respectively, but the net photosynthetic rates of 80% shaded and 40% shaded plants declined by 50% and 14.73%, respectively. Results showed that combined effect of soil moisture and shading on photosynthetic and stomatal responses in cotton leaves was very remarkable.
文摘Rhodiola sachalinensis growing in the different habitats, Xiaotianchi plot (altitude 1800 m), Tree line plot (altitude 2000 m) and Tianwenfeng plot (altitude 2325 m), of Changbai Moutain (northern slop) were transplanted to Harbin Experimental Forest Farm for measuring its characteristic of gas exchange. The study results indicated that the growth state and gas exchange characteristics ofRh. sachalinensis growing in different habitats varied markedly. The plants transplanted from Tianwenfeng plot had the highest values in net photosynthesis rate (Pn) and transpiration rate (Tr), those transplanted from Tree line plot shows the second, and those transplanted rom Xiaotianchi plot had the lowest values. The variance existed in transplanted plants was the same as shown in the field. From the result it can be extrapolated that the difference of Pn and Tr existed inRh. sachalinensis transplanted from different habitats is depend not only on the environmental factors, but on the variance of physiological characteristic of plant itself.
文摘Rhodiola sachalinensis growing in the different habitats, such as Xiaotianchi plot (altitude 1800 m), Tree line plot (altitude 2000 m) and Tianwenfeng plot (altitude 2325 m) of Changbai Mountain (northern slop) were transplanted to Harbin Experimental Farm for determining its gas exchange. The study results indicated that the diurnal changes of gas exchange ofRh. sachalinensis transplanted from different habitats were still different though the morphological appearance of the newly sprouted above-ground part had become more similar. For net photosynthesis rate (Pn), stomatal conductance (Gs) and apparent quantum yield (AQY), the diumal change curves ofRh. sachalinensis transplanted from the three plots were similar, but the data value were different. For the dark respiration rate (Rd), transpiration rate (Tr) and water use efficiency (WUE), diurnal change curves of the three plots were obviously different.
文摘Three-dimensional transient numerical simulation of gas exchange process in a four-stroke motorcycle engine with a semi-spherical combustion chamber with two tilt valves was studied. Combination of the grid re-meshing method and the snapper technique made the valves move smoothly. The flow structure and pattern in a complete engine cycle were described in detail. Tumble ratios around the x-axis and y-axis were analyzed. Comparison of computed pressure with experimental pressure under motored condition revealed that the simulation had high calculation precision; CFD simulation can be regarded as an im-portant tool for resolving the complex aerodynamic behavior in motorcycle engines.
基金funded by the National Natural Science Foundation of China(Nos.52206131,U2233213and 51775025)the National Key R&D Program of China(2022YFB2602002,2018YFB0104100)+1 种基金the Zhejiang Provincial Natural Science Foundation of China(LQ22E060004)the Science Center of Gas Turbine Project,China(No.P2022-A-I-001-001)。
文摘The in-cylinder gas exchange process is crucial to the power performance of two-stroke aircraft piston engines,which is easily influenced by complex factors such as high-altitude performance variation and in-cylinder flow characteristics.This paper reviews the development history and characteristics of gas exchange types,as well as the current state of theory and the validation methods of gas exchange technology,while also discusses the trends of cutting-edge technologies in the field.This paper provides a theoretical foundation for the optimization and engineering design of gas exchange systems and,more importantly,points out that the innovation of gas exchange types,the modification of theoretical models,and the technology of variable airflow organization are the key future research directions in this field.
基金funded by the Basic Research Program of the National Natural Science Foundation of China[grant numbers 52206131,U2333217,U2233213,and 51775025]National Key R&D Program of China[grant number 2022YFB2602002 and 2018YFB0104100]+1 种基金Zhejiang Provincial Natural Science Foundation of China[grant number LQ22E060004]Science Center of Gas Turbine Project[grant number P2022-A-I-001-001].
文摘The poppet valves two-stroke(PV2S)aircraft engine fueled with sustainable aviation fuel is a promising option for general aviation and unmanned aerial vehicle propulsion due to its high power-to-weight ratio,uniform torque output,and flexible valve timings.However,its high-altitude gas exchange performance remains unexplored,presenting new opportunities for optimization through artificial intelligence(AI)technology.This study uses validated 1D+3D models to evaluate the high-altitude gas exchange performance of PV2S aircraft engines.The valve timings of the PV2S engine exhibit considerable flexibility,thus the Latin hypercube design of experiments(DoE)methodology is employed to fit a response surface model.A genetic algorithm(GA)is applied to iteratively optimize valve timings for varying altitudes.The optimization process reveals that increasing the intake duration while decreasing the exhaust duration and valve overlap angles can significantly enhance high-altitude gas exchange performance.The optimal valve overlap angle emerged as 93°CA at sea level and 82°CA at 4000 m altitude.The effects of operating parameters,including engine speed,load,and exhaust back pressure,on the gas exchange process at varying altitudes are further investigated.The higher engine speed increases trapping efficiency but decreases the delivery ratio and charging efficiency at various altitudes.This effect is especially pronounced at elevated altitudes.The increase in exhaust back pressure will significantly reduce the delivery ratio and increase the trapping efficiency.This study demonstrates that integrating DoE with AI algorithms can enhance the high-altitude performance of aircraft engines,serving as a valuable reference for further optimization efforts.
基金the Natural Science Foundation of Hunan,China(No.2020JJ4159)the Research Foundation of Education Bureau of Hunan,China(No.19A093)+1 种基金the Interdisciplinary Program of Shanghai Jiao Tong University(No.YG2019ZDB08)the Significant Special Project form Ministry of Science and Technology of China(No.2021YFC0122500)。
文摘The high frequency ventilation(HFV)can well support the breathing of respiratory patient with 20%-40%of normal tidal volume.Now as a therapy of rescue ventilation when conversional ventilation failed,the HFV has been applied in the treatments of severe patients with acute respiratory failure(ARF),acute respiratory distress syndrome(ARDS),etc.However,the gas exchange mechanism(GEM)of HFV is still not fully understood by researchers.In this paper,the GEM of HFV is reviewed to track the studies in the last decades and prospect for the next likely studies.And inspired by previous studies,the GEM of HFV is suggested to be continually developed with various hypotheses which will be testified in simulation,experiment and clinic trail.One of the significant measures is to study the GEM of HFV under the cross-disciplinary integration of medicine and engineering.Fully understanding the GEM can theoretically support and expand the applications of HFV,and is helpful in investigating the potential indications and contraindications of HFV.
基金support of Russian Science Foundation (Project No.23-17-00148)as a part of R&D project (State registry No.121062200075-4).
文摘The article focuses on a theoretical and experimental framework for the quantification of interaction between nonlinear geomechnical and physicochemical processes in high-stress coal-bearing rock mass during mining under high seismic risk due to large-scale blasting and earthquakes,as well as because of structural and temperature effects.The tests were aimed to examine and study comprehensively the piston mechanism of gas exchange and mass transfer processes,revealed recently at the Institute of Mining,SB RAS,as well as to explain the fact that the earthquake-induced low-velocity(quasi-meter range)pendulum waves(velocity to 1 m/s and frequency of 0.5–5 Hz)could stimulate an increase in the gas content in coal mines.In order to perform laboratory investigation at the Institute of Mining SB RAS,special-purpose stand for analyzing gas exchange and mass transfer processes in coal-bearing geomaterials under various thermodynamic conditions(P,V,T)and gas composition was constructed in cooperation with the Institute of Semiconductors Physics SB RAS.Matching of air flow rate with compression pressures allowed to obtain relations showing that air flow rate increases at the uncertain time interval under the increasing of the compression pressure.The same measurements was carried out with another gases such as Hydrogen H_(2),Helium He,methane CH_(4),carbon dioxide CO_(2) and carbon oxide CO.The laboratory tests aimed to detailed investigation of the previously revealed“piston mechanism”of gas exchange and mass transfer processes in the coal specimens and their quantitative description in terms of theory of the pendulum waves were carried in the first time.Consequently,there are some arguments for the testing of the opportunity of quantitative description of the“piston mechanism”related to gas exchange and mass transfer processes in the scale of coal mines.It is relevant when pendulum waves induced by powerful earthquakes and technical blasting reaches the mine.
基金funding from the European Research Council (ERC)under grant agreement no.834134 (WATUSO)VLAIO for Moonshot funding (ARCLATH,No.HBC.2019.0110 and ARCLATH2,No.HBC.2021.0254)+3 种基金supported by the Flemish Government as an international research infrastructure (I001321N)infrastructure support by Department EWI via the Hermes Fund (AH.2016.134)the Hercules Foundation (AKUL/13/21)FWO Vlaanderen for an FWO-SB fellowship。
文摘1.Challenges circular methane energy systems In recent decades,methane-based energy systems have rapidly gained traction across the globe because of the increasing availability of low-cost methane production capacity.However,fossil methane production and combustion lead to large greenhouse gas emissions,contributing to climate change[1].
基金Supported by the Administration of Traditional Chinese Medicine Scientific Research of Zhejiang Province(No.2010ZA087)
文摘Objective： To compare the effect between nebulized and intravenous administration of Shenmai Injection （参麦注射液） on pulmonary gas exchange function of patients following tourniquet-induced lower limb ischemia-repeffusion. Methods： Thirty-eight patients scheduled for lower extremity surgery were randomized into three groups using the closed envelop method： Shenmai Injection was administered 30 min before tourniquet inflation by nebulization [0.6 mL/kg in 10 mL normal saline （NS）] in the nebulization group or by intravenous drip （0.6 mL/kg dissolved in 250 mL of 10% glucose） in the intravenous drip group, and equal volume of NS was given intravenously in the NS group; 15 in each group. Arterial blood gases were analyzed, serum levels of malonaldehyde （MDA） and interleukine-6 （IL-6） and interleukine-8 （IL-8） were determined using the method of thiobarbituric acid reaction and enzyme-linked immuno sorbent assay respectively just before tourniquet inflation （TO）, and at 0.5 h （T1）, 2 h （TZ）, 6 h （T3） after tourniquet deflation. Results： Compared with baselines at TO, MDA levels significantly increased at TZ, T3 in the NS group and at T3 in the nebulization group, and IL-6 and IL-8 levels were significantly increased at TZ, T3 in NS, the intravenous drip and the nebulization groups （P〈0.05）. Arterial pressure of oxygen （PaO2） at T3 was decreased, while alveolar- arterial oxygen tension showed difference （PA-aDO2） at T3 in the NS group; RI at T3 in both intravenous drip and the nebulization groups were enhanced （P〈0.05）. Compared with the NS group, MDA and IL-8 levels at TZ, T3, 11-6 at T3 in the intravenous drip group, and IL-8 at T3 in the nebulization group were all remarkably increased （P〈0.05）. Additionally, MDA level at T3 in the nebulization group was higher than that in the intravenous drip group （P〈0.05）. Conclusions： Intravenous administration of Shenmai Injection provided a better protective effect than nebulization in mitigating pulmonary gas exchange dysfunction in patients following tourniquet-induced limb ischemia-repertusion.
基金supported by the equipment grant(FONDEQUIP‐IQM 130073)from CONICYT‐Chilethe Doctoral research grantthe research program"Adaptation of Agriculture to Climate Change(A2C2),"both from Universidad de Talca‐Chile
文摘Chlorophyll and anthocyanin contents provide a valuable indicator of the status of a plant’s physiology, but to be more widely utilized it needs to be assessed easily and non‐destructively. This is particularly evident in terms of assessing and exploiting germplasm for plant‐breeding programs. We report, for the first time, experiments with Fragaria chiloensis（L.）Duch. and the estimation of the effects of response to salinity stress（0, 30, and 60 mmol NaCl/L） in terms of these pigments content and gas exchange. It is shown that both pigments（which interestingly, themselves show a high correlation） give a good indication of stress response. Both pigments can be accurately predicted using spectral reflectance indices（SRI）;however, the accuracy of the predictions was slightly improved using multilinear regression analysis models and genetic algorithm analysis. Specifically for chlorophyll content, unlike other species, the use of published SRI gave better indications ofstress response than Normalized Difference Vegetation Index.The effect of salt on gas exchange is only evident at the highest concentration and some SRI gave better prediction performance than the known Photochemical Reflectance Index. This information will therefore be useful for identifying tolerant genotypes to salt stress for incorporation in breeding programs.
基金Supported by the National Natural Science Foundation of China （30430430）, the Foundation for the Author of National Excellent Doctoral Dissertation of China （200152）, and the Teaching and Research Award Program for 0utstanding Young Teachers in Higher Education institution of M0E, China （2002-323）.
文摘In the present study, we Investigated the effects of Increaslng sallnlty on growth, gas exchange, absclslc acld （ABA）, calmodulln （CAM）, and the relevance to salt tolerance In seedllngs of Populus euphratlca Ollv. and cutUngs of P. ＂pupularls 35-44＂ （P. popularls） and P. x euramerlcana cv. 1-214 （P. cv. Itallca）. The relatlve growth rates of shoot helght （RGR,） for P. cv. Itallca and P. popularls were severely reduced by Increaslng salt stress, whereas the growth reductlon was relatlvely less in P. euphratica. Slmllarly, P. euphratlca malntalned hlgher net photosynthetlc rates （Pn） and unlt transplration rotes （TRN） than P. cv. Itallca and P. popularls under condltlons of hlgher sallnlty. Sallnity caused a slgnlficant increase In leaf ABA and CaM In the three genotypes after the onset of stress, but NaCl-induced ABA and CaM accumulatlon was more pronounced In P. euphratlca, suggeeUng that P. euphratlca plants are more sensitlve in sensing soil salinlty than the other two poplars. Furthermore, P. euphratica maintained relatively higher ABA and CaM concentrations under conditions of high salinity. The higher capacity to synthesize stress signals, namely ABA and CaM, In P. euphratica and the contrlbuUon of this to the salt resistance of P. euphratica are discussed.
基金National Natural Science Foundation of China(31000227)Ministry of Science and Technology of China(2013CB956300).
文摘Aims Climate change largely impacts ecosystem carbon and water cycles by changing plant gas exchange,which may further cause positive or negative feedback to global climate change.However,long-term global change manipulative experiments are seldom conducted to reveal plant ecophysiological responses to climatic warming and altered precipitation regimes.Methods An 8-year field experiment with both warming and increased precipitation was conducted in a temperate grassland in northern China.We measured leaf gas exchange rates(including plant photosynthesis,transpiration and instantaneous water use efficiency[WUE])of two dominant plant species(Stipa sareptana var.krylovii and Agropyron cristatum)from 2005 to 2012(except 2006 and 2010)and those of other six species from 2011 to 2012.Important Findings Increased precipitation significantly stimulated plant photosynthetic rates(A)by 29.5%and 19.9%and transpiration rates(E)by 42.2%and 51.2%for both dominant species S.sareptana var.krylovii and A.cristatum,respectively,across the 8 years.Similarly,A and E of the six plant functional types were all stimulated by increased precipitation in 2011 and 2012.As the balance of A and E,the instantaneous WUEs of different plant species had species-specific responses to increased precipitation.In contrast,neither warming nor its interaction with increased precipitation significantly affected plant leaf gas exchange rates.Furthermore,A and E of the two dominant species and their response magnitudes to water treatments positively correlated with rainfall amount in July across years.We did not find any significant difference between the short-term versus long-term responses of plant photosynthesis,suggesting the flexibility of leaf gas exchange under climate change.The results suggest that changing precipitation rather than global warming plays a prominent role in determining production of this grassland in the context of climate change.
基金supported by grants from the National Natural Science Foundation of China(31600483,31760111,31901091)the Outstanding Young Scholar of Jiangxi Science and Technology Innovation(20192BCBL23016)the Jiangxi Provincial Department of Education(GJJ190945).
文摘Aims Drought stress and the degree of drought severity are predicted to rise under highly variable patterns of precipitation due to climate change,while the capacity of trees to cope with drought recovery through physiological and biochemical adjustment remains unclear.We aimed to examine the coupling of physiology and biochemistry in trees during drought and the following recovery.Methods Potted seedlings of Cinnamomum camphora were grown under well watered conditions prior to the experimental drought stress,which was initiated by withholding water.Seedlings were rewatered following attainment of two drought severities:mild drought(stomatal closure)and moderate drought(ψxylem=−1.5 MPa).We measured leaf-level water potential,gas exchange(photosynthesis and stomatal conductance),abscisic acid(ABA),proline and non-structural carbohydrates(NSCs)concentrations in seedlings of C.camphora during drought and a 4-day recovery.Important Findings We found that drought severity largely determined physiological and biochemical responses and affected the rate of recovery.Stomatal closure occurred at the mild drought stress,accompanied with ABA accumulation in leaves and decline in water potential,while leaf proline accumulation and variable NSC were evident at the moderate drought stress.More severe drought stress led to delayed recovery of gas exchange,but it did not have significant effect on water potential recovery.The relationships of water potential and gas exchange differed during drought stress and post-drought recovery.There was tight coupling between water potential and gas exchange during drought,but not during rewatering due to high ABA accumulation in leaves,thereby delaying recovery of stomatal conductance.Our results demonstrate that ABA could be an important factor in delaying the recovery of stomatal conductance following rewatering and after water potential recovery of C.camphora.Furthermore,greater drought severity had significant impacts on the rate of recovery of tree physiology and biochemistry.
