Bionic microfluidics is garnering increasing attention due to the superior fluidic performance enabled by biomimetic microstructures.Inspired by the unique structures of young pumpkin stems,we fabricate helicoidally p...Bionic microfluidics is garnering increasing attention due to the superior fluidic performance enabled by biomimetic microstructures.Inspired by the unique structures of young pumpkin stems,we fabricate helicoidally patterned microchannels with precisely controlled morphologies using the projection micro-stereolithography(PμSL)-based 3D printing technique.Our helicoidally patterned microchannels achieve approximately twice the liquid lifting height compared to similarly sized smooth microchannels.This improvement is attributed to the enhanced capillary force.The additional meniscus formed between the helicoidally patterned microstructures significantly contributes to the increased capillary effects.Furthermore,the underlying mechanisms of fluidic performance in helicoidally patterned microchannels are theorized using a newly developed equation,which is also employed to optimize the geometric parameters and fluidic performance of the biomimetic helicoidal microchannels.Additionally,our biomimetic helicoidally patterned microchannels facilitate a significant step-lifting phenomenon,mimicking tall trees'transpiration.The fluidic performance of our biomimetic helicoidally patterned microchannels show promise for applications in enhanced liquid lifting,step-lifting,clean-water production,and others.展开更多
Background:Seasonal precipitation variability significantly affects water use in forests;however,whether water uptake is adapted to changes in precipitation,particularly whether it could affect the coexistence of tree...Background:Seasonal precipitation variability significantly affects water use in forests;however,whether water uptake is adapted to changes in precipitation,particularly whether it could affect the coexistence of tree species,has rarely been quantified in forest systems.Method:In this study,dual stable isotopes and the Li-6400 portable photosynthesis system were used to determine the water sources of a mixed conifer(Pinus massoniana)and broadleaf(Quercus acutissima)forest and changes in hydraulic characteristics during the dry and wet seasons in a southern hilly region of China.Results:Although the hydraulic characteristics of P.massoniana were lower than those of Q.acutissima,it maintained a stable water source from the deep soil layer and a higher stomatal conductance(Gs),leading to a higher transpiration rate(Tr)during the growing seasons.Q.acutissima mainly absorbed water from deeper soil layers in the dry season and took up from shallow soil layers in the wet season.Its Gs values exhibited sensitivity to precipitation,while it maintained a lower Tr value during the growing seasons.The excessive water-use strategy observed in P.massoniana may confer weak drought-tolerance during higher frequency and more intense extreme precipitation events,whereas Q.acutissima may exhibit better ecological adaption to precipitation changes.Conclusions:The overlap of water niches in mixed forests did not appear to affect the coexistence of tree species.The present study provides insights into reforestation and water management in the southern hilly regions of China.展开更多
Soil water content(SWC)and meteorological conditions,as key environmental variables influencing tree water use,vary highly within the growing season,hindering a better understanding of environmental control mechanisms...Soil water content(SWC)and meteorological conditions,as key environmental variables influencing tree water use,vary highly within the growing season,hindering a better understanding of environmental control mechanisms on canopy transpiration(Ec).Disentangling the effects of these variables on Ec across growing-season stages is crucial for Ec estimation and forest management.In this study,43-year-old Pinus tabuliformis Carr.and 31-yearold Platycladus orientalis(L.)Franco plantations in the semiarid Chinese Loess Plateau were monitored for Ec during the growing season of 2015-2020.The contributions of environmental factors to Ec were assessed using the boosted regression tree(BRT)model.Results showed that the contributions of SWC to Ec were greater at the early(May-June)and late(September)stages,while the contributions of vapor pressure deficit(VPD)and total solar radiation(Rs)to Ec increased at the middle(July-August)stage due to high soil water availability.Overall,Ec in both plantations was dominated by SWC(20.4%≤contributions≤48.8%)and Rs(22.7%≤contributions≤35.8%).Both species exhibited strong stomatal regulation of Ec.Specifically,stomatal opening was significantly inhibited by VPD at the early stage and strongly affected by SWC at the late stage.This study highlights that soil water conditions in artificial forests should be adjusted according to changes in influencing factors on Ec.Particularly during the early and late stages,measures(e.g.,land preparation,thinning,and pruning)can be implemented to improve soil moisture in such dryland forests.展开更多
Aiming at the global design issue of transpiration cooling thermal protection system,a self-driven circulation loop is proposed as the internal coolant flow passage for the transpiration cooling structure to achieve a...Aiming at the global design issue of transpiration cooling thermal protection system,a self-driven circulation loop is proposed as the internal coolant flow passage for the transpiration cooling structure to achieve adaptive cooling.To enhance the universality of this internal cooling pipe design and facilitate its application,numerical studies are conducted on this systemwith four commonly used cooling mediums as coolant.Firstly,the accuracy of the numerical method is verified through an established experimental platform.Then,transient numerical simulations are performed on the flow states of different cooling mediums in the new self-circulation system.Based on the numerical result,the flow,phase change,and heat transfer characteristics of different cooling mediums are analyzed.Differences in fluid velocity and latent heat of phase change result in significant variation in heat exchange capacity among different coolingmediums,with the maximumdifference reaching up to 3 times.Besides,faster circulation speed leads to greater heat transfer capacity,with a maximum of 7600 W/m^(2).Consequently,the operating mechanism and cooling laws of the natural circulation system is further investigated,providing a reference for the practical application of this system.展开更多
【Objective】Jatropha curcas is a potential source of biodiesel plant grown on waste and unattended lands,and parts of the areas are often suffered from flooding.The present study was conducted to develop a model to c...【Objective】Jatropha curcas is a potential source of biodiesel plant grown on waste and unattended lands,and parts of the areas are often suffered from flooding.The present study was conducted to develop a model to calculate the net CO_(2)assimilation rate,transpiration rate and stomatal conductance with respect to leaf position,which affect the J.curcas productivity under soil flooding.【Method】The process of developing mathematical models for physiological responses associated with parameterization,optimization and validation.The concept was applied for the calculation of net CO 2 assimilation rate from transpiration rate and stomatal conductance,transpiration rate from net CO_(2)assimilation rate and stomatal conductance,and stomatal conductance from net CO_(2)assimilation rate and transpiration rate in different leaf positions of J.curcas.The models were tested under soil flooding and normal conditions to suffice its wider applicability.A model was proposed to calculate net CO 2 assimilation rate,transpiration rate and stomatal conductance responses from a known set of response function data by calculating a transformation characteristic constant between any two possible paired response functions.【Result】The mean deviations and root mean square errors(RMSE)of calculated physiological responses were low,which validated the proposed hypothesis and statistical models.The approach was applied for modeling physiological responses successfully in J.curcas.RMSE ranged from1.69%to 11.17%when transpiration rate and stomatal conductance were transformed to net CO_(2)assimilation rate,and from 1.70%to 11.61%in case net CO_(2)assimilation rate and stomatal conductance were transformed to transpiration rate,and from 3.87%to 13.21%if net CO_(2)assimilation rate and transpiration rate were transformed to stomatal conductance,respectively.【Conclusion】The model can be useful for calculating cumulative responses under different conditions from a basic known set of data.The key to successful physiological models is finding the better options that are realistic,easy to understand,interpretative and practical between adherence to reality,comprehensibility,interpretative value,and practical usefulness on sustainable agriculture in years to come.展开更多
Evapotranspiration is the most important expenditure item in the water balance of terrestrial ecosystems,and accurate evapotranspiration modeling is of great significance for hydrological,ecological,agricultural,and w...Evapotranspiration is the most important expenditure item in the water balance of terrestrial ecosystems,and accurate evapotranspiration modeling is of great significance for hydrological,ecological,agricultural,and water resource management.Artificial forests are an important means of vegetation restoration in the western Loess Plateau,and accurate estimates of their evapotranspiration are essential to the management and development of water use strategies for artificial forests.This study estimated the soil moisture and evapotranspiration based on the HYDRUS-1D model for the artificial Platycladus orientalis(L.)Franco forest in western mountains of Loess Plateau,China from 20 April to 31 October,2023.Moreover,the influence factors were identified by combining the correlation coefficient method and the principal component analysis(PCA)method.The results showed that HYDRUS-1D model had strong applicability in portraying hydrological processes in this area and revealed soil water surplus from 20 April to 31 October,2023.The soil water accumulation was 49.64 mm;the potential evapotranspiration(ET_(p))was 809.67 mm,which was divided into potential evaporation(E_(p);95.07 mm)and potential transpiration(T_(p);714.60 mm);and the actual evapotranspiration(ET_(a))was 580.27 mm,which was divided into actual evaporation(E_(a);68.27 mm)and actual transpiration(T_(a);512.00 mm).From April to October 2023,the ET_(p),E_(p),T_(p),ET_(a),E_(a),and T_(a) first increased and then decreased on both monthly and daily scales,exhibiting a single-peak type trend.The average ratio of T_(a)/ET_(a) was 0.88,signifying that evapotranspiration mainly stemmed from transpiration in this area.The ratio of ET_(a)/ET_(p) was 0.72,indicating that this artificial forest suffered from obvious drought stress.The ET_(p) was significantly positively correlated with ET_(a),and the R^(2) values on the monthly and daily scales were 0.9696 and 0.9635(P<0.05),respectively.Furthermore,ET_(a) was significantly positively correlated with temperature,solar radiation,and wind speed,and negatively correlated with relative humidity and precipitation(P<0.05);and temperature exhibited the highest correlation with ET_(a).Thus,ET_(p) and temperature were the decisive contributors to ET_(a) in this area.The findings provide an effective method for simulating regional evapotranspiration and theoretical reference for water management of artificial forests,and deepen understanding of effects of each influence factors on ET_(a) in arid areas.展开更多
Background Water deficit is an important problem in agricultural production in arid regions.With the advent of wholly mechanized technology for cotton planting in Xinjiang,it is important to determine which planting m...Background Water deficit is an important problem in agricultural production in arid regions.With the advent of wholly mechanized technology for cotton planting in Xinjiang,it is important to determine which planting mode could achieve high yield,fiber quality and water use efficiency(WUE).This study aimed to explore if chemical topping affected cotton yield,quality and water use in relation to row configuration and plant densities.Results Experiments were carried out in Xinjiang China,in 2020 and 2021 with two topping method,manual topping and chemical topping,two plant densities,low and high,and two row configurations,i.e.,76 cm equal rows and 10+66 cm narrow-wide rows,which were commonly applied in matching harvest machine.Chemical topping increased seed cotton yield,but did not affect cotton fiber quality comparing to traditional manual topping.Under equal row spacing,the WUE in higher density was 62.4%higher than in the lower one.However,under narrow-wide row spacing,the WUE in lower density was 53.3%higher than in higher one(farmers’practice).For machine-harvest cotton in Xinjiang,the optimal row configuration and plant density for chemical topping was narrow-wide rows with 15 plants m-2 or equal rows with 18 plants m-2.Conclusion The plant density recommended in narrow-wide rows was less than farmers’practice and the density in equal rows was moderate with local practice.Our results provide new knowledge on optimizing agronomic managements of machine-harvested cotton for both high yield and water efficient.展开更多
Transpiration cooling is numerically investigated,where a cooling gas is injected through a carbon composite material into a hot gas channel.To account for microscale effects at the injection interface,an effective pr...Transpiration cooling is numerically investigated,where a cooling gas is injected through a carbon composite material into a hot gas channel.To account for microscale effects at the injection interface,an effective problem is derived.Here,effects induced by microscale structures on macroscale variables,e.g.,cooling efficiency,are taken into account without resolving the microscale structures.For this purpose,effective boundary conditions at the interface between hot gas and porous medium flow are derived using an upscaling strategy.Numerical simulations in 2D with effective boundary conditions are compared to uniform and non-uniform injection.The computations confirm that the effective model provides a more efficient and accurate approximation of the cooling efficiency than the uniform injection.展开更多
A dynamic plant architecture is the basis of plant adaptation to changing environments.Although many genes regulating leaf rolling have been identified,genes directly associated with water homeostasis are largely unkn...A dynamic plant architecture is the basis of plant adaptation to changing environments.Although many genes regulating leaf rolling have been identified,genes directly associated with water homeostasis are largely unknown.Here,we isolated a rice mutant,dynamic leaf rolling 1(dlr1),characterized by‘leaf unfolding in the morning-leaf rolling at noon-leaf unfolding in the evening’during a sunny day.Water content was decreased in rolled leaves and water sprayed on leaves caused reopening,indicating that in vivo water deficiency induced the leaf rolling.Map-based cloning and expression tests demonstrated that an A1400G single base mutation in Oryza sativa Polygalacturonase 1(OsPG1)/PHOTO-SENSITIVE LEAF ROLLING 1(PSL1)was responsible for the dynamic leaf rolling phenotype in the dlr1 mutant.OsPG1 encodes a polygalacturonase,one of the main enzymes that degrade demethylesterified homogalacturonans in plant cell walls.OsPG1 was constitutively expressed in various tissues and was enriched in stomata.Mutants of the OsPG1 gene exhibited defects in stomatal closure and decreased stomatal density,leading to reduced transpiration and excessive water loss under specific conditions,but had normal root development.Further analysis revealed that mutation of OsPG1 led to reduced pectinase activity in the leaves and increased demethylesterified homogalacturonans in guard cells.Our findings reveal a mechanism by which OsPG1 modulates water homeostasis to control dynamic leaf rolling,providing insights for plants to adapt to environmental variation.展开更多
Accurate nitrogen(N)nutrition diagnosis is essential for improving N use efficiency in crop production.The widely used critical N(Nc)dilution curve traditionally depends solely on agronomic variables,neglecting crop w...Accurate nitrogen(N)nutrition diagnosis is essential for improving N use efficiency in crop production.The widely used critical N(Nc)dilution curve traditionally depends solely on agronomic variables,neglecting crop water status.With three-year field experiments with winter wheat,encompassing two irrigation levels(rainfed and irrigation at jointing and anthesis)and three N levels(0,180,and 270 kg ha1),this study aims to establish a novel approach for determining the Nc dilution curve based on crop cumulative transpiration(T),providing a comprehensive analysis of the interaction between N and water availability.The Nc curves derived from both crop dry matter(DM)and T demonstrated N concentration dilution under different conditions with different parameters.The equation Nc=6.43T0.24 established a consistent relationship across varying irrigation regimes.Independent test results indicated that the nitrogen nutrition index(NNI),calculated from this curve,effectively identifies and quantifies the two sources of N deficiency:insufficient N supply in the soil and insufficient soil water concentration leading to decreased N availability for root absorption.Additionally,the NNI calculated from the Nc-DM and Nc-T curves exhibited a strong negative correlation with accumulated N deficit(Nand)and a positive correlation with relative grain yield(RGY).The NNI derived from the Nc-T curve outperformed the NNI derived from the Nc-DM curve concerning its relationship with Nand and RGY,as indicated by larger R2 values and smaller AIC.The novel Nc curve based on T serves as an effective diagnostic tool for assessing winter wheat N status,predicting grain yield,and optimizing N fertilizer management across varying irrigation conditions.These findings would provide new insights and methods to improve the simulations of water-N interaction relationship in crop growth models.展开更多
Carex planostachys Kunze (Cyperaceae, Cedar sedge) is an herbaceous species in a genus commonly inhabiting mesic or hydric habitats. Carex planostachys is found in arid and semi-arid Juniperus woodlands. Arid conditio...Carex planostachys Kunze (Cyperaceae, Cedar sedge) is an herbaceous species in a genus commonly inhabiting mesic or hydric habitats. Carex planostachys is found in arid and semi-arid Juniperus woodlands. Arid conditions impose survival challenges to plants in dry areas. Some plants have plasticity responses to soil water content and continued normal though reduced functions through droughts, but most herbaceous plants do not survive. Limited previous studies have suggested C. planostachys is tolerant of drought. Physiological responses of C. planostachys from Juniperus woodlands was examined is this study to determine how long plants could survive without water and if they are capable of recovery from very negative water potentials beyond what is considered the permanent wilting point for most herbaceous plants. Plants were placed in pots in partial shade in this experiment. Water loss from the soil with plants was an inverse 2nd order polynomial function with soil water decreasing from 32% to 8% by day 28 of the study. Leaf water potential was also an inverse 2nd order polynomial function but did not decline significantly until 14 days without watering. Leaf water potential was −10.0 MPa after 35 days without watering. Non-watered plants Anet, (photosynthetic rate) was significantly lower compared to the water treatment by day 21 as was stomatal conductance and transpiration. When non-watered plants were watered after 21, 28 or 35 days, full recovery of physiological responses occurred within 7 days. The length of time that C. planostachys was able to withstand drought was greater than the annual trends in lack of precipitation during springtime in this area. Carex planostachys can photosynthesize at water stress between −8 and −10 MPa. Carex planostachys drought and shade tolerance enables it to occupy an understory niche devoid of other herbaceous plants.展开更多
Similar to transpiration,the formulation of interfacial solar evaporation has been designed to perform water treatment.The concept involves wood-based support(tree)with a graphene-based layer acting as leaves.To enhan...Similar to transpiration,the formulation of interfacial solar evaporation has been designed to perform water treatment.The concept involves wood-based support(tree)with a graphene-based layer acting as leaves.To enhance light absorption and solar-thermal conversion capacity,a novel holly-leaf graphene(HLG)layer with an individual hollowed-out structure was engineered.The formation mechanism of this HLG was shown to be linked to the strong capillarity forces in the polyporous wood.By creating biomimetic leaves made of graphene,the light-to-heat conversion performance can be improved,while exhibiting substantially lower thermal conductivity(0.074 W/(m K))than natural wood.Under solar irradiation,HLG/wood exhibits an outstanding evaporation rate of 1.96 kg/(m^(2)h),with an impressive ef-ficiency of 94.2%.A theoretical model of HLG/wood based on the thermal management capability was built to further confirm its structural superiority in facilitating photothermal conversion.Consequently,a bilayer evaporator based on HLG/wood has the potential to revolutionize water purification processes,including desalination of seawater,removal of heavy metal ions,and treatment of organic dye-contaminated wastewater.展开更多
We investigated the osmotic stress and ion-specific effects on xylem abscisic acid (ABA), ion uptake and transport and gas exchange in one-year-old seedlings of Populus euphratica Oliv. Net photosynthetic rates (P-n) ...We investigated the osmotic stress and ion-specific effects on xylem abscisic acid (ABA), ion uptake and transport and gas exchange in one-year-old seedlings of Populus euphratica Oliv. Net photosynthetic rates (P-n) and unit transpiration rates (TRN) were both significantly decreased upon an osmotic shock caused by PEG 6000 solution (osmotic potential = -0.24 MPa) or a saline, which was applied by 50 mmol/L Na+-salts (NaNO3 : NaHCO3 : NaH2PO4 = 5 : 4 : 1, pH 6.8, osmotic potential = -0.24 MPa) or by 50 mmol/L Cl--salts (KCl : NH4Cl = 1:1, osmotic potential = -0.24 MPa). However, salt-treated P. euphratica plants maintained typically higher TRN than those exposed to PEG. Xylem ABA concentrations increased rapidly following the PEG treatment, exhibiting peaking values at 1 h, then returning to pre-stress levels, followed by a gradual increase. Similarly, both Na+-treated and Cl--treated trees exhibited a rapid rise of ABA after salt stress was initiated. Notably, salt-treated plants maintained a relatively higher ABA than PEG-treated plants in a longer term. Collectively, results suggest that osmotic stress and ion-specific effects were both responsible for salt-induced ABA in P. euphratica : the initial rapid increase of xylem ABA appears to be a consequence of an osmotic shock, whereas specific salt effects seem to be responsible for ABA accumulation later on. Compared with Cl--treated trees, a higher inhibitory effect on gas exchange (P-n and TRN) was observed in Na+-salt plants, resulting from its long-sustained ABA and higher salt concentrations in the xylem. Displacement of membrane-associated Ca2+ by Na+ and the lesser capacity in Na+ compartmentation in root vacuoles likely contribute to the high influx of Na+ and Cl- in Na+-treated plants. Xylem K+, Ca2+ and Mg2+ concentrations were elevated by external Na+ -salts and Cl--salts, suggesting that P. euphratica maintained a higher capacity in nutrient uptake under saline conditions, which makes a contribution to its salinity tolerance.展开更多
Photosynthesis ( P n ), transpiration ( E ) and water use efficiency ( WUE ) of more than 66 arid sand species from different environmental habitats, shifting sand dune, fixed sand dune, lowland and wetland in ...Photosynthesis ( P n ), transpiration ( E ) and water use efficiency ( WUE ) of more than 66 arid sand species from different environmental habitats, shifting sand dune, fixed sand dune, lowland and wetland in the Maowusu Sand Area were analyzed and the relation among these characteristics and the resource utilization efficiency, taxonomic categories and growth forms of the species were assessed. The results showed that species from Chenopodiaceae, Gramineae, Leguminosae which possessed the C 4 photosynthesis pathway, or C 3 pathway and also with nitrogen_fixation capacities had higher or the highest P n values, i.e., 20～30 μmol CO 2·m -2 ·s -1 , while that of evergreen shrub of Pinaceae had the lowest P n values, i.e., 0～5 μmol CO 2·m -2 ·s -1 . Those species from Compositae, Scrophulariaceae, and Gramineae with C 3 pathway but no N_fixation capacity had the highest E rates, i.e., 20～30 mmol H 2O·m -2 ·s -1 and again the evergreen shrub together with some species from Salicaceae and Compositae had the lowest E rates, i.e., 0～5 mmol H 2O·m -2 ·s -1 . Species from Leguminosae, Gramineae and Chenopodiaceae with C 4 pathway or C 3 pathway with N_fixation capacity, both shrubs and grasses, generally had higher WUE . However, even the physiological traits of the same species were habitat_ and season_specific. The values of both P n and E in late summer were much higher than those in early summer, with average increases of 26%, 40% respectively in the four habitats. WUE in late summer was, however, 12% lower. Generally, when the environments became drier as a result of habitats changed, i.e., in the order of wetland, lowland, fixed sand dune and shifting sand dune, P n and E decreased but WUE increased.展开更多
Transpiration element is included in the integrated stomatal conductance photosynthesis model by considering gaseous transfer processes, so the present model is capable to simulate the influence of boundary layer con...Transpiration element is included in the integrated stomatal conductance photosynthesis model by considering gaseous transfer processes, so the present model is capable to simulate the influence of boundary layer conductance. Leuning in his revised Ball's model replaced relative humidity with VPD s (the vapor pressure deficit from stomatal pore to leaf surface) and thereby made the relation with transpiration more straightforward, and made it possible for the regulation of transpiration and the influence of boundary layer conductance to be integrated into the combined model. If the differences in water vapor and CO 2 concentration between leaf and ambient air are considered, VPD s , the evaporative demand, is influenced by stomatal and boundary layer conductance. The physiological responses of photosynthesis, transpiration, and stomatal function, and the changes of intercellular CO 2 and water use efficiency to environmental factors, such as wind speed, photon flux density, leaf temperature and ambient CO 2, are analyzed. It is shown that if the boundary layer conductance drops to a level comparable with stomatal conductance, the results of simulation by the model presented here differ significantly from those by the previous model, and, in some cases, are more realistic than the latter.展开更多
Soil moisture of Leymus chinensis (Trin.) Tzvel. community has obviously stratified phenomena: the layer (0-40 cm) in which roots are concentrically distributed is directly influenced by precipitation and evapotranspi...Soil moisture of Leymus chinensis (Trin.) Tzvel. community has obviously stratified phenomena: the layer (0-40 cm) in which roots are concentrically distributed is directly influenced by precipitation and evapotranspiration. It can be called interaction layer of precipitation and evapotranspiration. The layer (40-120 cm), where water-storage capacity exchange lagged exchange of the root-layer water-storage capacity and the community evapotranspiration, can be called major water-storage layer. The layer (under 120 cm) can be called water relatively stable/balanced layer. The year 1996 was a normal flow year, and soil water had a surplus of 18 mm at the end of the growing season. The year 1998 was a high flow year, because leakage took place under continuous heavy rainfall, soil water had a deficit of 15 mm at the end of the growing season. Transpiration to evapotranspiration ( T/ET) value reflected not only the luxuriance degree of the community, but also the water use regime of the environmental resources. T/ET value was low (0.5) in May 1998, reaching 0.7 in June, then decreasing to 0.6 in July, due to the impact of rainfall inclining, while August reached the maximum (0.9), and September decreased to 0.6. Water use efficiency (WUE) was mainly restricted by the growing rate of plants under sufficient water condition (1998). Its seasonal changes were coincident with the grand period of growth of the plants. When both meanings of WUE and T/ET were analyzed profoundly, the concept of evapotranspiration efficiency (ETE) which can all-side reflect utilization regime of the environmental water resources was advanced.展开更多
Soil water stress was studied on the potted seedlings of five dominant tree species (Pinus koraienes Sieb.et Zucc., Fraxinus mandshurica Rupr., Juglans mandshurica Maxim, Tilia amurensis Rupr. and Quercus mongolica Fi...Soil water stress was studied on the potted seedlings of five dominant tree species (Pinus koraienes Sieb.et Zucc., Fraxinus mandshurica Rupr., Juglans mandshurica Maxim, Tilia amurensis Rupr. and Quercus mongolica Fisch.ex Turcz) from the broadleaved/Korean pine forest in Changbai Mountain. Leaf growth, water transpiration and photosynthesis were compared for each species under three soil moisture conditions: 85%-100% (high water, CK), 65%-85% (Medium water, MW) and 45%-65% (low water, LW) of 37.4% water-holding capacity in field. The results showed that the characteristic of typical drought-resistance of the leaves is significantly developed. The net photosynthetic rate and water use efficiency of Fraxinus mandshurica were higher in MW than those in CK. But for the other four species, the net photosynthetic rate and water use efficiency in CK were lower than those in MW and LW. The transpiration rate responding to soil moistures varied from species to species.展开更多
The effects of different vibration intensities harvesting on photosynthesis system parameters of Lycium barbarum L. tree with harvest machine were researched. The result showed that the photosynthetic rate, transpirat...The effects of different vibration intensities harvesting on photosynthesis system parameters of Lycium barbarum L. tree with harvest machine were researched. The result showed that the photosynthetic rate, transpiration rate, stomata conductance and intercellular CO2 concentration of L. barbarum tree＇s leaves under different treatment during different periods have no significant difference compared with contrast. It indicates that there is no significant effect on photosynthesis system parameters of L. barbarum tree＇s leaves with harvest machine.展开更多
To know the annual water consumption of forest, it is necessary to acquire the annual transpiration value of stands. This paper is based on the data measured in the typical weather of the growth season, from 1998 to 2...To know the annual water consumption of forest, it is necessary to acquire the annual transpiration value of stands. This paper is based on the data measured in the typical weather of the growth season, from 1998 to 2000, with the LI 1600 Steady Porometer and the general weather information. The daily variation of transpiration in black locust forest ( Robinia pesudoacacia L.) is modeled by Penman Monteith equation. As a result of the model, a continuous daily transpiration in the growth season was calculated. The net radiation, intercepted by black locust forest canopy, was acquired from a semi empirical equation of measuring net radiation R n with the extinction coefficient k and leaf area index LAI . The canopy integral stomatic resistance is a mimesis with an empirical equation of measuring data. Compared with measuring data, the relative error of the modeled ones is less than 12% averagely. At last, the total transpiration of black locust forest during the period of 1998 and 2000 in the growth season of May to October, as an average transpiration of the different density stands, were 192 46, 187 07 and 195 59?mm respectively.展开更多
[ Objective ] The paper was to explore the pathogenic mechanism of tomato powdery mildew, and to study the effects of the disease on photosynthetic characteristics of tomato. [ Method ] With four tomato varieties as m...[ Objective ] The paper was to explore the pathogenic mechanism of tomato powdery mildew, and to study the effects of the disease on photosynthetic characteristics of tomato. [ Method ] With four tomato varieties as materials, the pathogen of tomato powdery mildew was artificially inoculated. After the varieties were infected, the parameters including net photosynthetic rate, stomatal conductance and transpiration rate of tomato leaf were measured by Li-6400 portable photo- synthesis detector under natural lighting conditions. [ Result] The net photosynthetic rate, stomatal conductance and transpiration rate of four tomato varieties all decreased after infection. However, the decrease extent of these parameters of four varieties was different. The parameters of seriously damaged Jinyangdajuxdng （ No. 4） and Xinsheng No. 1 （ No. 5 ） decreased greatly, while the parameters of slightly damaged Lujia （ No. 13 ） and improved 98-6 decreased lightly. [ Condu- sion] The results could provide theoretical basis for the study on pathogenic mechanism, new prevention way and resistance breeding of tomato powdery mildew.展开更多
基金supported by National Natural Science Foundation of China through Grant Nos.52495000,52332012 and 52176093partially supported by Beijing Huiyangdao Health Technology Co.,Ltd。
文摘Bionic microfluidics is garnering increasing attention due to the superior fluidic performance enabled by biomimetic microstructures.Inspired by the unique structures of young pumpkin stems,we fabricate helicoidally patterned microchannels with precisely controlled morphologies using the projection micro-stereolithography(PμSL)-based 3D printing technique.Our helicoidally patterned microchannels achieve approximately twice the liquid lifting height compared to similarly sized smooth microchannels.This improvement is attributed to the enhanced capillary force.The additional meniscus formed between the helicoidally patterned microstructures significantly contributes to the increased capillary effects.Furthermore,the underlying mechanisms of fluidic performance in helicoidally patterned microchannels are theorized using a newly developed equation,which is also employed to optimize the geometric parameters and fluidic performance of the biomimetic helicoidal microchannels.Additionally,our biomimetic helicoidally patterned microchannels facilitate a significant step-lifting phenomenon,mimicking tall trees'transpiration.The fluidic performance of our biomimetic helicoidally patterned microchannels show promise for applications in enhanced liquid lifting,step-lifting,clean-water production,and others.
基金supported by the National Natural Science Foundation of China(No.42377068)Jiangsu Provincial Natural Science Foundation(No.BK20231290)Yinshanbeilu Grassland Eco-hydrology National Observation and Research Station(China Institute of Water Resources and Hydropower Research,No.YSS2022003)the Qing Lan Project。
文摘Background:Seasonal precipitation variability significantly affects water use in forests;however,whether water uptake is adapted to changes in precipitation,particularly whether it could affect the coexistence of tree species,has rarely been quantified in forest systems.Method:In this study,dual stable isotopes and the Li-6400 portable photosynthesis system were used to determine the water sources of a mixed conifer(Pinus massoniana)and broadleaf(Quercus acutissima)forest and changes in hydraulic characteristics during the dry and wet seasons in a southern hilly region of China.Results:Although the hydraulic characteristics of P.massoniana were lower than those of Q.acutissima,it maintained a stable water source from the deep soil layer and a higher stomatal conductance(Gs),leading to a higher transpiration rate(Tr)during the growing seasons.Q.acutissima mainly absorbed water from deeper soil layers in the dry season and took up from shallow soil layers in the wet season.Its Gs values exhibited sensitivity to precipitation,while it maintained a lower Tr value during the growing seasons.The excessive water-use strategy observed in P.massoniana may confer weak drought-tolerance during higher frequency and more intense extreme precipitation events,whereas Q.acutissima may exhibit better ecological adaption to precipitation changes.Conclusions:The overlap of water niches in mixed forests did not appear to affect the coexistence of tree species.The present study provides insights into reforestation and water management in the southern hilly regions of China.
基金supported by the National Key Research&Development Project of China(No.2022YFF1300403)the National Natural Science Foundation of China(Nos.U21A2011,41971129,and 32401663)the Open Fund of the State Key Laboratory of Loess Science(No.SKLLQG2423).
文摘Soil water content(SWC)and meteorological conditions,as key environmental variables influencing tree water use,vary highly within the growing season,hindering a better understanding of environmental control mechanisms on canopy transpiration(Ec).Disentangling the effects of these variables on Ec across growing-season stages is crucial for Ec estimation and forest management.In this study,43-year-old Pinus tabuliformis Carr.and 31-yearold Platycladus orientalis(L.)Franco plantations in the semiarid Chinese Loess Plateau were monitored for Ec during the growing season of 2015-2020.The contributions of environmental factors to Ec were assessed using the boosted regression tree(BRT)model.Results showed that the contributions of SWC to Ec were greater at the early(May-June)and late(September)stages,while the contributions of vapor pressure deficit(VPD)and total solar radiation(Rs)to Ec increased at the middle(July-August)stage due to high soil water availability.Overall,Ec in both plantations was dominated by SWC(20.4%≤contributions≤48.8%)and Rs(22.7%≤contributions≤35.8%).Both species exhibited strong stomatal regulation of Ec.Specifically,stomatal opening was significantly inhibited by VPD at the early stage and strongly affected by SWC at the late stage.This study highlights that soil water conditions in artificial forests should be adjusted according to changes in influencing factors on Ec.Particularly during the early and late stages,measures(e.g.,land preparation,thinning,and pruning)can be implemented to improve soil moisture in such dryland forests.
基金funded by Fei He,National Natural Science Foundation of China(contract no.52376154)Anhui Provincial Natural Science Foundation(contract no.2308085J21).
文摘Aiming at the global design issue of transpiration cooling thermal protection system,a self-driven circulation loop is proposed as the internal coolant flow passage for the transpiration cooling structure to achieve adaptive cooling.To enhance the universality of this internal cooling pipe design and facilitate its application,numerical studies are conducted on this systemwith four commonly used cooling mediums as coolant.Firstly,the accuracy of the numerical method is verified through an established experimental platform.Then,transient numerical simulations are performed on the flow states of different cooling mediums in the new self-circulation system.Based on the numerical result,the flow,phase change,and heat transfer characteristics of different cooling mediums are analyzed.Differences in fluid velocity and latent heat of phase change result in significant variation in heat exchange capacity among different coolingmediums,with the maximumdifference reaching up to 3 times.Besides,faster circulation speed leads to greater heat transfer capacity,with a maximum of 7600 W/m^(2).Consequently,the operating mechanism and cooling laws of the natural circulation system is further investigated,providing a reference for the practical application of this system.
文摘【Objective】Jatropha curcas is a potential source of biodiesel plant grown on waste and unattended lands,and parts of the areas are often suffered from flooding.The present study was conducted to develop a model to calculate the net CO_(2)assimilation rate,transpiration rate and stomatal conductance with respect to leaf position,which affect the J.curcas productivity under soil flooding.【Method】The process of developing mathematical models for physiological responses associated with parameterization,optimization and validation.The concept was applied for the calculation of net CO 2 assimilation rate from transpiration rate and stomatal conductance,transpiration rate from net CO_(2)assimilation rate and stomatal conductance,and stomatal conductance from net CO_(2)assimilation rate and transpiration rate in different leaf positions of J.curcas.The models were tested under soil flooding and normal conditions to suffice its wider applicability.A model was proposed to calculate net CO 2 assimilation rate,transpiration rate and stomatal conductance responses from a known set of response function data by calculating a transformation characteristic constant between any two possible paired response functions.【Result】The mean deviations and root mean square errors(RMSE)of calculated physiological responses were low,which validated the proposed hypothesis and statistical models.The approach was applied for modeling physiological responses successfully in J.curcas.RMSE ranged from1.69%to 11.17%when transpiration rate and stomatal conductance were transformed to net CO_(2)assimilation rate,and from 1.70%to 11.61%in case net CO_(2)assimilation rate and stomatal conductance were transformed to transpiration rate,and from 3.87%to 13.21%if net CO_(2)assimilation rate and transpiration rate were transformed to stomatal conductance,respectively.【Conclusion】The model can be useful for calculating cumulative responses under different conditions from a basic known set of data.The key to successful physiological models is finding the better options that are realistic,easy to understand,interpretative and practical between adherence to reality,comprehensibility,interpretative value,and practical usefulness on sustainable agriculture in years to come.
基金financially supported by the National Natural Science Foundation of China(42071047,41771035)the Basic Research Innovation Group Project of Gansu Province(22JR5RA129)the Excellent Doctoral Program in Gansu Province(24JRRA152).
文摘Evapotranspiration is the most important expenditure item in the water balance of terrestrial ecosystems,and accurate evapotranspiration modeling is of great significance for hydrological,ecological,agricultural,and water resource management.Artificial forests are an important means of vegetation restoration in the western Loess Plateau,and accurate estimates of their evapotranspiration are essential to the management and development of water use strategies for artificial forests.This study estimated the soil moisture and evapotranspiration based on the HYDRUS-1D model for the artificial Platycladus orientalis(L.)Franco forest in western mountains of Loess Plateau,China from 20 April to 31 October,2023.Moreover,the influence factors were identified by combining the correlation coefficient method and the principal component analysis(PCA)method.The results showed that HYDRUS-1D model had strong applicability in portraying hydrological processes in this area and revealed soil water surplus from 20 April to 31 October,2023.The soil water accumulation was 49.64 mm;the potential evapotranspiration(ET_(p))was 809.67 mm,which was divided into potential evaporation(E_(p);95.07 mm)and potential transpiration(T_(p);714.60 mm);and the actual evapotranspiration(ET_(a))was 580.27 mm,which was divided into actual evaporation(E_(a);68.27 mm)and actual transpiration(T_(a);512.00 mm).From April to October 2023,the ET_(p),E_(p),T_(p),ET_(a),E_(a),and T_(a) first increased and then decreased on both monthly and daily scales,exhibiting a single-peak type trend.The average ratio of T_(a)/ET_(a) was 0.88,signifying that evapotranspiration mainly stemmed from transpiration in this area.The ratio of ET_(a)/ET_(p) was 0.72,indicating that this artificial forest suffered from obvious drought stress.The ET_(p) was significantly positively correlated with ET_(a),and the R^(2) values on the monthly and daily scales were 0.9696 and 0.9635(P<0.05),respectively.Furthermore,ET_(a) was significantly positively correlated with temperature,solar radiation,and wind speed,and negatively correlated with relative humidity and precipitation(P<0.05);and temperature exhibited the highest correlation with ET_(a).Thus,ET_(p) and temperature were the decisive contributors to ET_(a) in this area.The findings provide an effective method for simulating regional evapotranspiration and theoretical reference for water management of artificial forests,and deepen understanding of effects of each influence factors on ET_(a) in arid areas.
基金Key Research and Development Program of Xinjiang(2022B02001-1)National Natural Science Foundation of China(42105172,41975146).
文摘Background Water deficit is an important problem in agricultural production in arid regions.With the advent of wholly mechanized technology for cotton planting in Xinjiang,it is important to determine which planting mode could achieve high yield,fiber quality and water use efficiency(WUE).This study aimed to explore if chemical topping affected cotton yield,quality and water use in relation to row configuration and plant densities.Results Experiments were carried out in Xinjiang China,in 2020 and 2021 with two topping method,manual topping and chemical topping,two plant densities,low and high,and two row configurations,i.e.,76 cm equal rows and 10+66 cm narrow-wide rows,which were commonly applied in matching harvest machine.Chemical topping increased seed cotton yield,but did not affect cotton fiber quality comparing to traditional manual topping.Under equal row spacing,the WUE in higher density was 62.4%higher than in the lower one.However,under narrow-wide row spacing,the WUE in lower density was 53.3%higher than in higher one(farmers’practice).For machine-harvest cotton in Xinjiang,the optimal row configuration and plant density for chemical topping was narrow-wide rows with 15 plants m-2 or equal rows with 18 plants m-2.Conclusion The plant density recommended in narrow-wide rows was less than farmers’practice and the density in equal rows was moderate with local practice.Our results provide new knowledge on optimizing agronomic managements of machine-harvested cotton for both high yield and water efficient.
基金Funding Open Access funding enabled and organized by Projekt DEAL.Financial support has been provided by the German Research Foundation(Deutsche Forschungsgemeinschaft-DFG)in the framework of the Sonderforschungsbereich Transregio 40.
文摘Transpiration cooling is numerically investigated,where a cooling gas is injected through a carbon composite material into a hot gas channel.To account for microscale effects at the injection interface,an effective problem is derived.Here,effects induced by microscale structures on macroscale variables,e.g.,cooling efficiency,are taken into account without resolving the microscale structures.For this purpose,effective boundary conditions at the interface between hot gas and porous medium flow are derived using an upscaling strategy.Numerical simulations in 2D with effective boundary conditions are compared to uniform and non-uniform injection.The computations confirm that the effective model provides a more efficient and accurate approximation of the cooling efficiency than the uniform injection.
基金This work was supported by the Postgraduate Research Innovation Project of Chongqing(CYS23217)Chongqing Modern Agricultural Industry Technology System(CQMAITS202301)+1 种基金the Science Fund for Creative Research Groups of the Natural Science Foundation of Chongqing,China(cstc2021jcyj-cxttX0004)Natural Science Foundation of Chongqing(2023NSCQ-BHX0281).
文摘A dynamic plant architecture is the basis of plant adaptation to changing environments.Although many genes regulating leaf rolling have been identified,genes directly associated with water homeostasis are largely unknown.Here,we isolated a rice mutant,dynamic leaf rolling 1(dlr1),characterized by‘leaf unfolding in the morning-leaf rolling at noon-leaf unfolding in the evening’during a sunny day.Water content was decreased in rolled leaves and water sprayed on leaves caused reopening,indicating that in vivo water deficiency induced the leaf rolling.Map-based cloning and expression tests demonstrated that an A1400G single base mutation in Oryza sativa Polygalacturonase 1(OsPG1)/PHOTO-SENSITIVE LEAF ROLLING 1(PSL1)was responsible for the dynamic leaf rolling phenotype in the dlr1 mutant.OsPG1 encodes a polygalacturonase,one of the main enzymes that degrade demethylesterified homogalacturonans in plant cell walls.OsPG1 was constitutively expressed in various tissues and was enriched in stomata.Mutants of the OsPG1 gene exhibited defects in stomatal closure and decreased stomatal density,leading to reduced transpiration and excessive water loss under specific conditions,but had normal root development.Further analysis revealed that mutation of OsPG1 led to reduced pectinase activity in the leaves and increased demethylesterified homogalacturonans in guard cells.Our findings reveal a mechanism by which OsPG1 modulates water homeostasis to control dynamic leaf rolling,providing insights for plants to adapt to environmental variation.
基金supported by the National Key Research and Development Program of China(2022YFD2001005)the Key Research&Development Program of Jiangsu province(BE2021358)+2 种基金the National Natural Science Foundation of China(32271989)the Natural Science Foundation of Jiangsu province(BK20220146)the Jiangsu Independent Innovation Fund Project of Agricultural Science and Technology[CX(23)3121].
文摘Accurate nitrogen(N)nutrition diagnosis is essential for improving N use efficiency in crop production.The widely used critical N(Nc)dilution curve traditionally depends solely on agronomic variables,neglecting crop water status.With three-year field experiments with winter wheat,encompassing two irrigation levels(rainfed and irrigation at jointing and anthesis)and three N levels(0,180,and 270 kg ha1),this study aims to establish a novel approach for determining the Nc dilution curve based on crop cumulative transpiration(T),providing a comprehensive analysis of the interaction between N and water availability.The Nc curves derived from both crop dry matter(DM)and T demonstrated N concentration dilution under different conditions with different parameters.The equation Nc=6.43T0.24 established a consistent relationship across varying irrigation regimes.Independent test results indicated that the nitrogen nutrition index(NNI),calculated from this curve,effectively identifies and quantifies the two sources of N deficiency:insufficient N supply in the soil and insufficient soil water concentration leading to decreased N availability for root absorption.Additionally,the NNI calculated from the Nc-DM and Nc-T curves exhibited a strong negative correlation with accumulated N deficit(Nand)and a positive correlation with relative grain yield(RGY).The NNI derived from the Nc-T curve outperformed the NNI derived from the Nc-DM curve concerning its relationship with Nand and RGY,as indicated by larger R2 values and smaller AIC.The novel Nc curve based on T serves as an effective diagnostic tool for assessing winter wheat N status,predicting grain yield,and optimizing N fertilizer management across varying irrigation conditions.These findings would provide new insights and methods to improve the simulations of water-N interaction relationship in crop growth models.
文摘Carex planostachys Kunze (Cyperaceae, Cedar sedge) is an herbaceous species in a genus commonly inhabiting mesic or hydric habitats. Carex planostachys is found in arid and semi-arid Juniperus woodlands. Arid conditions impose survival challenges to plants in dry areas. Some plants have plasticity responses to soil water content and continued normal though reduced functions through droughts, but most herbaceous plants do not survive. Limited previous studies have suggested C. planostachys is tolerant of drought. Physiological responses of C. planostachys from Juniperus woodlands was examined is this study to determine how long plants could survive without water and if they are capable of recovery from very negative water potentials beyond what is considered the permanent wilting point for most herbaceous plants. Plants were placed in pots in partial shade in this experiment. Water loss from the soil with plants was an inverse 2nd order polynomial function with soil water decreasing from 32% to 8% by day 28 of the study. Leaf water potential was also an inverse 2nd order polynomial function but did not decline significantly until 14 days without watering. Leaf water potential was −10.0 MPa after 35 days without watering. Non-watered plants Anet, (photosynthetic rate) was significantly lower compared to the water treatment by day 21 as was stomatal conductance and transpiration. When non-watered plants were watered after 21, 28 or 35 days, full recovery of physiological responses occurred within 7 days. The length of time that C. planostachys was able to withstand drought was greater than the annual trends in lack of precipitation during springtime in this area. Carex planostachys can photosynthesize at water stress between −8 and −10 MPa. Carex planostachys drought and shade tolerance enables it to occupy an understory niche devoid of other herbaceous plants.
基金supported by the National Natural Science Foun-dation of China(Nos.32171709 and 32271791)the Forestry Science and Technology Innovation of Hunan Province(No.XLK202107-3)the Scientific Research Project of Hunan Education Department(No.21B0242).
文摘Similar to transpiration,the formulation of interfacial solar evaporation has been designed to perform water treatment.The concept involves wood-based support(tree)with a graphene-based layer acting as leaves.To enhance light absorption and solar-thermal conversion capacity,a novel holly-leaf graphene(HLG)layer with an individual hollowed-out structure was engineered.The formation mechanism of this HLG was shown to be linked to the strong capillarity forces in the polyporous wood.By creating biomimetic leaves made of graphene,the light-to-heat conversion performance can be improved,while exhibiting substantially lower thermal conductivity(0.074 W/(m K))than natural wood.Under solar irradiation,HLG/wood exhibits an outstanding evaporation rate of 1.96 kg/(m^(2)h),with an impressive ef-ficiency of 94.2%.A theoretical model of HLG/wood based on the thermal management capability was built to further confirm its structural superiority in facilitating photothermal conversion.Consequently,a bilayer evaporator based on HLG/wood has the potential to revolutionize water purification processes,including desalination of seawater,removal of heavy metal ions,and treatment of organic dye-contaminated wastewater.
文摘We investigated the osmotic stress and ion-specific effects on xylem abscisic acid (ABA), ion uptake and transport and gas exchange in one-year-old seedlings of Populus euphratica Oliv. Net photosynthetic rates (P-n) and unit transpiration rates (TRN) were both significantly decreased upon an osmotic shock caused by PEG 6000 solution (osmotic potential = -0.24 MPa) or a saline, which was applied by 50 mmol/L Na+-salts (NaNO3 : NaHCO3 : NaH2PO4 = 5 : 4 : 1, pH 6.8, osmotic potential = -0.24 MPa) or by 50 mmol/L Cl--salts (KCl : NH4Cl = 1:1, osmotic potential = -0.24 MPa). However, salt-treated P. euphratica plants maintained typically higher TRN than those exposed to PEG. Xylem ABA concentrations increased rapidly following the PEG treatment, exhibiting peaking values at 1 h, then returning to pre-stress levels, followed by a gradual increase. Similarly, both Na+-treated and Cl--treated trees exhibited a rapid rise of ABA after salt stress was initiated. Notably, salt-treated plants maintained a relatively higher ABA than PEG-treated plants in a longer term. Collectively, results suggest that osmotic stress and ion-specific effects were both responsible for salt-induced ABA in P. euphratica : the initial rapid increase of xylem ABA appears to be a consequence of an osmotic shock, whereas specific salt effects seem to be responsible for ABA accumulation later on. Compared with Cl--treated trees, a higher inhibitory effect on gas exchange (P-n and TRN) was observed in Na+-salt plants, resulting from its long-sustained ABA and higher salt concentrations in the xylem. Displacement of membrane-associated Ca2+ by Na+ and the lesser capacity in Na+ compartmentation in root vacuoles likely contribute to the high influx of Na+ and Cl- in Na+-treated plants. Xylem K+, Ca2+ and Mg2+ concentrations were elevated by external Na+ -salts and Cl--salts, suggesting that P. euphratica maintained a higher capacity in nutrient uptake under saline conditions, which makes a contribution to its salinity tolerance.
文摘Photosynthesis ( P n ), transpiration ( E ) and water use efficiency ( WUE ) of more than 66 arid sand species from different environmental habitats, shifting sand dune, fixed sand dune, lowland and wetland in the Maowusu Sand Area were analyzed and the relation among these characteristics and the resource utilization efficiency, taxonomic categories and growth forms of the species were assessed. The results showed that species from Chenopodiaceae, Gramineae, Leguminosae which possessed the C 4 photosynthesis pathway, or C 3 pathway and also with nitrogen_fixation capacities had higher or the highest P n values, i.e., 20～30 μmol CO 2·m -2 ·s -1 , while that of evergreen shrub of Pinaceae had the lowest P n values, i.e., 0～5 μmol CO 2·m -2 ·s -1 . Those species from Compositae, Scrophulariaceae, and Gramineae with C 3 pathway but no N_fixation capacity had the highest E rates, i.e., 20～30 mmol H 2O·m -2 ·s -1 and again the evergreen shrub together with some species from Salicaceae and Compositae had the lowest E rates, i.e., 0～5 mmol H 2O·m -2 ·s -1 . Species from Leguminosae, Gramineae and Chenopodiaceae with C 4 pathway or C 3 pathway with N_fixation capacity, both shrubs and grasses, generally had higher WUE . However, even the physiological traits of the same species were habitat_ and season_specific. The values of both P n and E in late summer were much higher than those in early summer, with average increases of 26%, 40% respectively in the four habitats. WUE in late summer was, however, 12% lower. Generally, when the environments became drier as a result of habitats changed, i.e., in the order of wetland, lowland, fixed sand dune and shifting sand dune, P n and E decreased but WUE increased.
文摘Transpiration element is included in the integrated stomatal conductance photosynthesis model by considering gaseous transfer processes, so the present model is capable to simulate the influence of boundary layer conductance. Leuning in his revised Ball's model replaced relative humidity with VPD s (the vapor pressure deficit from stomatal pore to leaf surface) and thereby made the relation with transpiration more straightforward, and made it possible for the regulation of transpiration and the influence of boundary layer conductance to be integrated into the combined model. If the differences in water vapor and CO 2 concentration between leaf and ambient air are considered, VPD s , the evaporative demand, is influenced by stomatal and boundary layer conductance. The physiological responses of photosynthesis, transpiration, and stomatal function, and the changes of intercellular CO 2 and water use efficiency to environmental factors, such as wind speed, photon flux density, leaf temperature and ambient CO 2, are analyzed. It is shown that if the boundary layer conductance drops to a level comparable with stomatal conductance, the results of simulation by the model presented here differ significantly from those by the previous model, and, in some cases, are more realistic than the latter.
文摘Soil moisture of Leymus chinensis (Trin.) Tzvel. community has obviously stratified phenomena: the layer (0-40 cm) in which roots are concentrically distributed is directly influenced by precipitation and evapotranspiration. It can be called interaction layer of precipitation and evapotranspiration. The layer (40-120 cm), where water-storage capacity exchange lagged exchange of the root-layer water-storage capacity and the community evapotranspiration, can be called major water-storage layer. The layer (under 120 cm) can be called water relatively stable/balanced layer. The year 1996 was a normal flow year, and soil water had a surplus of 18 mm at the end of the growing season. The year 1998 was a high flow year, because leakage took place under continuous heavy rainfall, soil water had a deficit of 15 mm at the end of the growing season. Transpiration to evapotranspiration ( T/ET) value reflected not only the luxuriance degree of the community, but also the water use regime of the environmental resources. T/ET value was low (0.5) in May 1998, reaching 0.7 in June, then decreasing to 0.6 in July, due to the impact of rainfall inclining, while August reached the maximum (0.9), and September decreased to 0.6. Water use efficiency (WUE) was mainly restricted by the growing rate of plants under sufficient water condition (1998). Its seasonal changes were coincident with the grand period of growth of the plants. When both meanings of WUE and T/ET were analyzed profoundly, the concept of evapotranspiration efficiency (ETE) which can all-side reflect utilization regime of the environmental water resources was advanced.
基金national key basic develop-ment of China (G1999043407), grant from the National Natural Science Foundation of China (No. 30271068) and KZ-CX-SW-01-01B of the Chinese Academy of Sciences.
文摘Soil water stress was studied on the potted seedlings of five dominant tree species (Pinus koraienes Sieb.et Zucc., Fraxinus mandshurica Rupr., Juglans mandshurica Maxim, Tilia amurensis Rupr. and Quercus mongolica Fisch.ex Turcz) from the broadleaved/Korean pine forest in Changbai Mountain. Leaf growth, water transpiration and photosynthesis were compared for each species under three soil moisture conditions: 85%-100% (high water, CK), 65%-85% (Medium water, MW) and 45%-65% (low water, LW) of 37.4% water-holding capacity in field. The results showed that the characteristic of typical drought-resistance of the leaves is significantly developed. The net photosynthetic rate and water use efficiency of Fraxinus mandshurica were higher in MW than those in CK. But for the other four species, the net photosynthetic rate and water use efficiency in CK were lower than those in MW and LW. The transpiration rate responding to soil moistures varied from species to species.
基金Supported by Natural Science Foundation of Ningxia Hui Autonomous Region(NZ0852)~~
文摘The effects of different vibration intensities harvesting on photosynthesis system parameters of Lycium barbarum L. tree with harvest machine were researched. The result showed that the photosynthetic rate, transpiration rate, stomata conductance and intercellular CO2 concentration of L. barbarum tree＇s leaves under different treatment during different periods have no significant difference compared with contrast. It indicates that there is no significant effect on photosynthesis system parameters of L. barbarum tree＇s leaves with harvest machine.
基金SupportedbytheNationalNaturalScienceFoundationofChina(39970 6 2 2 )andtheTeachingandResearchAwardProgramforYongCadremanTeachersinHigherEducationInstitutionsofMOE P .R .China
文摘To know the annual water consumption of forest, it is necessary to acquire the annual transpiration value of stands. This paper is based on the data measured in the typical weather of the growth season, from 1998 to 2000, with the LI 1600 Steady Porometer and the general weather information. The daily variation of transpiration in black locust forest ( Robinia pesudoacacia L.) is modeled by Penman Monteith equation. As a result of the model, a continuous daily transpiration in the growth season was calculated. The net radiation, intercepted by black locust forest canopy, was acquired from a semi empirical equation of measuring net radiation R n with the extinction coefficient k and leaf area index LAI . The canopy integral stomatic resistance is a mimesis with an empirical equation of measuring data. Compared with measuring data, the relative error of the modeled ones is less than 12% averagely. At last, the total transpiration of black locust forest during the period of 1998 and 2000 in the growth season of May to October, as an average transpiration of the different density stands, were 192 46, 187 07 and 195 59?mm respectively.
基金Supported by Research Foundation of Sichuan Education Department "Utilization of Diversity of Tomato Varieties for Continuous Control of Tomato Disea-ses"(07ZC047)~~
文摘[ Objective ] The paper was to explore the pathogenic mechanism of tomato powdery mildew, and to study the effects of the disease on photosynthetic characteristics of tomato. [ Method ] With four tomato varieties as materials, the pathogen of tomato powdery mildew was artificially inoculated. After the varieties were infected, the parameters including net photosynthetic rate, stomatal conductance and transpiration rate of tomato leaf were measured by Li-6400 portable photo- synthesis detector under natural lighting conditions. [ Result] The net photosynthetic rate, stomatal conductance and transpiration rate of four tomato varieties all decreased after infection. However, the decrease extent of these parameters of four varieties was different. The parameters of seriously damaged Jinyangdajuxdng （ No. 4） and Xinsheng No. 1 （ No. 5 ） decreased greatly, while the parameters of slightly damaged Lujia （ No. 13 ） and improved 98-6 decreased lightly. [ Condu- sion] The results could provide theoretical basis for the study on pathogenic mechanism, new prevention way and resistance breeding of tomato powdery mildew.
