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Water stress has been one of the most serious threat to the crop growth, development and yield quality in agricultural fields. Timely and accurate diagnosis of crop water stress can greatly contribute to the precision irrigation for the crop resilience and yield. In this study, the research object was taken from the summer maize in the typical dryland agricultural area of northwest China. A six-channel multispectral sensor was mounted on a drone to obtain the remote sensing image data of summer maize at the nodulatione and staminate pulling stage in 2022. At the same time, the stomatal conductance and phenotypic parameters of summer maize were also collected. The background was removed by supervised classification. The canopy vegetation index and image texture were obtained using the gray-scale covariance matrix. The sensitive vegetation index, image texture and phenotypic parameters and their combinations were screened out by the Bayesian information criterion and full subset filtering. The summer maize stomatal conductance estimation model was constructed to combine the three types of machine learnings: the extreme learning machine, the random forest, and the back-propagation neural network. The optimal model was mapped to estimate the stomatal conductance. The Pearson correlation coefficient of vegetation index and stomatal conductance were significantly positively correlated, whereas, the canopy reflectance of summer maize was weakly negatively correlated. Different types of image textures at different wavelengths were correlated with the stomatal conductance, and the highest correlation was found in the 550 nm band. The Pearson correlation coefficients between morphological structure phenotypes (plant height, stem thickness and leaf area) and stomatal conductance of summer maize were 0.72, 0.58 and 0.69, respectively, where the three types of phenotypic parameters data were correlated well with stomatal conductance. Vegetation indices with spectral reflectance data were used to assess the overall health and moisture status of the vegetation. Image texture was used to capture the spatial distribution, texture and structural features of crops. Crop phenotypic parameters were then used to reflect the physiological and morphological responses of the crop in a three-dimensional manner, providing visual information about the growth and moisture of the vegetation. The decision coefficients of the crop water stress diagnostic models that constructed from the three information sources increased from 0.728 and 0.750 to 0.841, respectively, compared with the single or two combinations, indicating the great potential to stomatal conductance prediction. The optimal combination of indicators was screened by Bayesian information criterion and full subset screening: DWSI, NDVI, MEA, ENT, plant height and leaf area. The back-propagation neural network model with the three complementary information sources was the optimal model for the water stress diagnosis of summer maize (coefficient of determination of 0.841, root mean square error of 0.043 mol/(m2 ·s), and mean absolute error of 0.034 mol/(m² ·s)). The underestimation of stomatal conductance was significantly improved, compared with the rest models. The inverse map with the optimal model was widely applied to easily and accurately diagnose the crop water stress for the purpose of irrigation strategies and resource allocation. The finding can provide a feasible and accurate diagnosis of water stress in summer maize. [ABSTRACT FROM AUTHOR]

【Objective】 Transpiration is not only an important hydrological process but also a footprint of primary productivity of terrestrial systems under different environments. Its calculation at large scale is challenging. This paper proposes a method to fill this gap. 【Method】 The method is based on the modified Penman-Monteith (PM) model. The canopy resistance in the model is estimated using soil moisture based on the Ortega-Farias model, and the hydrodynamic resistance is calculated by two methods: one is based on wind speed and canopy temperature-environment relationship, and the other one is the Perrier logarithm method. The model was applied to simulate transpiration of citrus trees under water stress from June to July in 2022; its accuracy was evaluated against ground-true data. 【Result】 Water stress significantly reduced stomatal conductance and transpiration of the citrus trees. The canopy resistance estimated by the Ortega-Farias model agreed with the measured data with R2 = 0.63, accurately capturing the diurnal variation in canopy resistance under water stress. The aerodynamic resistance calculated by the leaf-based method was significantly greater than estimated by the Perrier logarithmic method. The accuracy of aerodynamic resistance calculated by the Perrier logarithmic method varied with soil water content, and the R2 between the measured and calculated transpiration from the PM model decreased from 0.66 when the plant was under slight water stress to 0.2 when the plant was under severe stress. In contrast, for the transpiration calculated using the aerodynamic resistances estimated by the leaf-simulation method, the R2 decreased from 0.71 to 0.24 with the increase in water stress. 【Conclusion】 When the soil moisture was greater than 50% of the field capacity, using the Ortega-Farias model to estimate canopy resistance and the leaf-based method to estimate aerodynamic resistance can improve the accuracy of the PM model for simulating transpiration of the citrus trees under water stress.

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The Salix matsudana were used as experimental material to study the effect of salt stree on the photosynthetic diurnal variation.The results showed that the photosynthetic rate of Salix matsudana showed a bimodal type in the standard contrast and mild stress conditions，while showed a single peak type in the moderate and severe stress condition with a trend first rise then falling.The stomatal conductance showed a bimodal type in the standard contrast and mild stress conditions，while showed a single peak type in the moderate and severe stress conditions with a trend of gradual decline.The daily variation trends of transpiration rate was similar with the stomatal conductance.The intercellular CO2 concentration under stress treatment were higher than the standard contrast，and increased with the salt stress levels. [ABSTRACT FROM AUTHOR]

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【Objective】 Turgor pressure in crops varies with root water uptake as a response to occurrence of water stress. This paper investigates how turgor pressure in the leaf of celery responds to drip irrigation and the factors which affect the pressure variation. 【Method】 The experiment was conducted in a greenhouse. It consists of sufficient irrigation (FI) and deficit irrigation (NI) treatment. Change in leave turgor pressure, characterized by expansion parameters Pp and Pp*, in each treatment was measured using a probe. We also measured the environmental factors and physiological traits of the plant, and analyzed their relationship with Pp/Pp* using multiple regression, path analysis and time warping methods. 【Result】 ① The parameter Pp* maximized at daytime and minimized at night on typical sunny days, regardless of the irrigation treatments and growing stage. However, Pp* started to increase earlier in NI than in FI treatment, with the peak of Pp* in the former being 39.3%~66.7% higher than that in the latter. ② The diurnal change in Pp* was similar to that in the stomatal conductance (Gs) and transpiration rate (Tr). Pp* was positively correlated to Gs and Tr, but negatively to leaf water potential (Ψ). ③ The change in leaf turgor pressure varied with irrigation. The maximum and minimum Pp increased gradually priori to irrigation and decreased rapidly after irrigation, especially in the NI treatment where the change was more profound. ④ Pp* was positively correlated to atmospheric temperature (TA) and vapour pressure deficit (VPD), but negatively to relative humidity (RH) and wind speed (WS). Path analysis showed that the highest correlation between Pp* and TA, and VPD was an indirect factor affecting Pp*. Stepwise regression indicated that WS impacted Pp* significantly only in NI. We also found that the impact of TA on Pp* was not instant but existed a delay, especially in NI where the delay was more than 10~30 min than that in FI. 【Conclusion】 Variation in leaf turgor pressure in greenhouse celery was closely related to irrigation amount and meteorological factors. Insufficient irrigation increased the maximum turgor-pressure variation parameter but delayed the effect of atmospheric temperature on the turgor pressure.

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Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study aims to determine the optimal response model of stomatal conductance to the Camellia oleifera leaves in hilly areas of south China. A portable photosynthetic apparatus (LCI-SD) was used to observe the leaves of three healthy Camellia oleifera trees in four directions of southeast, northwest every 10 days from June to September in 2020 and 2021. The field test was performed at Hunan National Camellia oleifera Engineering Technology Research Center in Changsha City, Hunan Province, China. A miniature automatic meteorological observation U30 Station (HOBO ware) was utilized to record synchronously the stomatal conductance, net photosynthetic rate, and CO2 concentration in the leaves, together with the meteorological data, such as atmospheric temperature, relative humidity, and photosynthetically active radiation. Then, the stomatal conductance of leaf was simulated using the Jarvis models with nine combinations, the Ball-Woodrow-Berry (BWB) and Ball-Berry-Leuning (BBL) model with two CO2 concentrations of leaf and intercellular. The Jarvis-8 and BBL model were modified to compare the introduced temperature of camellia oil leaves, and the CO2 concentration inside and outside stomata. A nonlinear regression and least square method were used to determine each parameter by the SPSS25.0 software platform. The results show that the influence of soil water or leaf water potential could be ignored when using the Jarvis model in the hilly region of southern China. It infers that the Jarvis model was dependent mainly on the photosynthetically active radiation, saturation vapor pressure deficit and temperature. Therefore, the soil water or leaf water potential was be ignored, when the Jarvis model was used in the hilly region of southern China. A better simulation effect was achieved in the Jarvis-8, BWB, and BBL model calculated by the leaf CO2 concentration. Among them, the BBL model presented the largest determination coefficient (R²=0.763) and the smallest absolute mean error (MAE=0.015), indicating the best effect. By contrast, the BWB model presented the smallest determination coefficient (R²=0.599), and the maximum mean absolute error (MAE=0.020), indicating the worst simulation effect. After two parameters were introduced, the simulation effect of leaf temperature difference was improved in the Jarvis-8 and BBL model, but not significantly. The CO2 concentration difference between inside and outside the stomatal was significantly improved the accuracy of the BBL model, where the determination coefficient increased from 0.763 to 0.950, and the slope of the model was very close to 1 (1.004), indicating the better consistence between the simulation and the measured stomatal conductance value. But, there was no change of the Jarvis-8 model in this case. A better simulation was achieved for the stomatal conductance values of leaves in the key growth periods of Camellia oleifera in 2020 (R²=0.92) and 2021 (R²=0.95), and the variation values of stomatal conductance degree-days under different scenarios. On the whole, the simulation performance was ranked in the descending order of the BBL-C model, BBL-Tmodel, BBL model, Jarvis-T model, Jarvis model, and Jarvis-C model. Therefore, the stomatal conductance response model of Camellia oleifera leaves can be recommended to introduce the BBL model with the CO2 concentration difference between stomatal. These findings can provide a strong reference to select a suitable stomatal conductance model for the large-scale Camellia oleifera in the hilly region of southern China. [ABSTRACT FROM AUTHOR]

Copyright of Arid Zone Research / Ganhanqu Yanjiu is the property of Arid Zone Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Canopy stomatal conductance indicates the intensity of photosynthesis and respiration of a plant, particularly for the evapotranspiration, agricultural production and ecosystem function. The estimated accuracy of canopy stomatal conductance varies greatly among different vegetation types. However, the influence of vegetation types on canopy stomatal conductance has rarely been considered in most previous studies. This study aims to develop a canopy stomatal conductance model considering vegetation types, thereby to achieve higher accuracy than before. According to a widely-used model of canopy stomatal conductance proposed by Leuning in 2008, two improvements were focused mainly on: 1) Stomatal length and density were introduced into the new model to calculate the maximum stomatal conductance, which differed among vegetation types but usually been calculated via parameter optimizing by minimizing the cost function. 2) Satellite-derived photosynthetically active radiation data was used to calculate the flux density of visible radiation at the top of canopy, instead of the net absorbed radiation minus the soil heat flux in previous studies, where the flux can contain the absorption by non-vegetation component. Ground observations were used to validate the model via the inversion of Penman-Monteith equation, including eddy covariance and automatic meteorological data from 15 sites in the middle reaches of Heihe Basin (100°20′-100°24′ E, 37°45′-42°40′ N) in China. An attempt was made to partition the evapotranspiration into soil evaporation and plant transpiration, where only plant transpiration was selected to derive canopy stomatal conductance, ruling out the influence of soil evaporation. Evaluation indexes included the determination coefficient, root mean square error (RMSE), and mean absolute error (MAE). The results were as follows: 1) The improved model achieved higher accuracy in the land cover of maize and bell pepper, where the ground observed data was used to validate the models before and after partitioning soil evaporation and plant transpiration by the inversion of Penman-Monteith equation. Specifically, the determination coefficient of maize improved from 0.49 to 0.68 after improvement, while the RMSE reduced from 3.99 to 2.67 mm/s, and the MAE reduced from 3.34 to 2.06 mm/s, after partitioning soil evaporation and plant transpiration. Before that, the determination coefficient of maize improved from 0.38 to 0.46 after improvement, with both RMSE and MAE reduced. 2) The new improved model was applied to the middle reaches of Heihe Basin from July to September 2012 using HJ-1 satellite data, including the leaf area index, photosynthetically active radiation, and land cover data. The model showed a good ability in estimating the canopy stomatal conductance of different vegetation types. The average value for the canopy conductance of maize on July 27 was 15.12 mm/s, while that of spruce was 3.84 mm/s. The determination coefficient improved from 0.51 to 0.70, and the RMSE reduced from 4.91 to 3.32 mm/s, comparing with the model before and after improvement. The commission error was calculated to evaluate whether the new model was sensitive to stomatal characteristics, indicating that there was an obvious difference, only when the vegetation was wrongly classified. It demonstrated that the remote sensing data can be used for the better accuracy of new model in various vegetation types. A better improvement was achieved in estimating canopy stomatal conductance using the new model considering vegetation types, compared with the traditional models without considering that. The finding can bring great convenience to scientific research, such as surface energy balance and carbon-water cycle, as well as the specific practical applications in precision agriculture, water resources management, and ecology. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Crops Improvement / Majallah-i Bih/zirā̒ī-i Kishāvarzī is the property of University of Tehran and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Bulletin of Botanical Research is the property of Bulletin of Botanical Research Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aiming at the phenomenon of excess nitrogen (N) application rate in winter wheat field in North China Plain, measuring and modelling photosynthetic rates under different N rates is helpful to understand the physiological basis of the influence of reducing traditional N application rates on crop yield. This study set up 3 amounts of N rates, i.e. 290, 190 and 110 kg/hm2, as high (N3), middle (N2) and low N (N1) treatments, respectively in drip irrigation winter wheat field in 2 consecutive growing seasons (2012-2014). The coupled model of photosynthesis and stomatal conductance was established to model photosynthetic rates. Photosynthetic rates to intercellular CO2 concentration response curves (An-Ci curves) were measured in 2014 to determine key parameters of the model from the heading stage to harvest stage. Daily dynamics of photosynthetic rates were measured in 2013 as the verification data of the coupled model. The results showed that the apparent maximum carboxylation rate of Rubisco (Vcmax) and maximum electron transfer rate (Jmax) was significantly affected by N treatments. The measured Vcmax varied from 84.5 to 153.3 μmol/(m2·s) and Jmax varied from 156.5 to 236.2 μmol/(m2·s) during the measurements and among treatments. Differences of Vcmax and Jmax among treatments were more significant when the measurement dates close to the harvest stage. During the filling stage (May 21st to 23rd), only Vcmax and Jmax of the low N treatment (N1) was significantly lower than that of high N treatment (N3), the corresponding values of the middle N treatment (N2) were not significant lower than those of N3. During the milking stage (June 2nd to 3rd), however, the Vcmax and Jmax of both N2 and N1 were significantly lower than those of N3. There was no significant difference in the ratio of Jmax/Vcmax among treatments during the three measurements. The ratio of Jmax/Vcmax gradually increased along with the advancing of growing stages and changed from 1.49 to 2.00 during the measurements. The differences of Vcmax among treatments could be quantified by leaf mass N content. Then the Jmax value can be calculated according to the ratio of Jmax/Vcmax. The slope (g1) and intercept (g0) of the stomatal conductance sub-model were changed with different N application. During the filling stage (May 21st to 23rd), it was found that the N3 treatment with the highest g0 and the smallest g1. The analytical solution of the photosynthesis model and the Ball-Berry stomatal conductance model was derived to solve the coupled model. Considering the difference between the key parameters, the simulation results of the coupling model for photosynthetic rate from the daily process was good, with the average absolute error were 2.11 and 2.23 μmol/(m2·s) for the 2 measurements in 2013 and the differences between simulated and measured photosynthetic rate were less than 5%. The prediction of the model also showed that different parameters have different effects on the simulation results of photosynthetic rate. For example, although the g0 of stomatal conductance sub-model is often relatively small, it will cause large error in the simulation of photosynthetic rate under low light intensity, while some researchers may neglect this parameter when running the model. The model can be used to simulate photosynthetic rates under change of single physiological or environmental factor and change of multi factors, so as to better predict the yield changes. [ABSTRACT FROM AUTHOR]

Copyright of Acta Agronomica Sinica is the property of Crop Science Society of China and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Henan Agricultural Sciences is the property of Editorial Board of Journal of Henan Agricultural Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Ground cover rice production system (GCRPS) has attracted great attention. The rice root system of GCRPS is under water stress, it is necessary to establish root water uptake models to quantify its root-water-uptake. The aim of this study was to investigate the relationship between transpiration (i.e. root-water-uptake) and root length, and thereupon to establish a root-water-uptake model under GCRPS. Furthermore, the Penman-Monteith (PM) equation was replaced by the validated root water uptake model to estimate transpiration rate and improve the traditional stomatal conductance model proposed by Tardieu-Davies (TD) in this study. A field experiment with 3 irrigation levels (named as TPRPS, GCRPSsat and GCRPS80%) was conducted in 2013 at Shiyan, Hubei province. Each treatment was designed and replicated 3 times in 9 plots, with an area of 9×10 m2. For treatment TPRPS, a water layer of 2-5 cm in thickness was always maintained on the soil beds. For GCRPSsat, soil water content in the root zone was kept close to saturation by completely filling the furrows with water but without water layer on the soil beds. For GCRPS80%, the management was the same way as that for GCRPSsat before mid-tillering stage, and then transient irrigation was intermittently implemented through the furrows to keep soil water content in the root zone between 80%-100% of field water-water holding capacity. A seepage-proof material was laid around each plot to the depth of 80 cm to avoid lateral percolation between neighbor plots. Five soil beds in each plot were built for planting rice, with the space of 26×18 cm2. Small furrows (15 cm in width and depth) were dug around each soil bed. The water saving characteristics of GCRPS were analyzed as a function of the measured soil water conditions, water input and consumption, and plant parameters regarding root growth and physical parameter were also determined. The soil water content under GCRPS was measured with a capacitance probe. Roots in each soil layer were washed via a sieve and analyzed for root length. Stomatal conductance of flag leaves were measured using a portable photosynthesis system. Experimental results showed that the potential transpiration rate was linearly proportional to the total root length of rice (R2=0.96, P<0.05). The root-water-uptake model established on the linear relationship simulated the dynamics of transpiration under GCRPS successfully, with the relative errors between simulated and measured transpiration rates less than 15%. The PM equation was replaced by the validated root water uptake model to estimate transpiration rate and to improve the TD model. The daily dynamics of stomatal conductance under GCRPS was simulated with the improved TD model by combining the established root water uptake model. The improved TD model was applied to estimate the ABA concentration of root water flow in various soil layers and evaluate the contribution of ABA synthesized in each root layer to that in transpiration flow in xylem. Compared with the traditional TD model, the improved TD model simulated the daily dynamics of stomatal conductance more accurately, with relative error less than 7.0% and root mean square error of 0.02 mol/(m2·s). This study can provide valuable information for understanding the physiological water saving mechanism and water use efficiency evaluation of GCRPS. [ABSTRACT FROM AUTHOR]

Knowledge of multi-scale evapotranspiration (ET) is the basis of increasing agricultural water use efficiency and realizing optimal water resources allocation. However, there is little information about the characteristics of multi-scale ET and the difference in the quantitative response of leaf and plant transpiration and farm-scale ET to the meteorological factors, especially for the solar greenhouse, which limits our understanding of agricultural water and energy cycles. In this study, the ET at different scales was investigated in solar greenhouse tomato and their main influential factors were analyzed. Experiments were carried out in a typical solar greenhouse to investigate variation in leaf and plant transpiration and farmland ET of drip-irrigated tomato under different water conditions in 2 continuous seasons. Field trials were conducted during the growing season from March to June, 2015 and 2016 at Xinxiang Comprehensive Experimental Station, Chinese Academy of Agricultural Sciences (35°9′N, 113°47′E, and an altitude of 78.7 m), located in Xinxiang, Henan province. Tomato was used in the experiment on a plot of 8.8 m2 (8.0 m long by 1.1 m wide) with 2 rows and 50 plants. There are 4 replications for each treatment. Tomato seedlings were transplanted on March 8th, 2015 and March 9th, 2016 respectively and irrigated with a drip irrigation system. Irrigation amount was determined based on the accumulated evaporation in 20 cm pan, and 2 treatments were designed with full irrigation and deficit irrigation. Leaf transpiration was measured with a photosynthesis system, plant transpiration (expressed as sap flow rate) measured by a sap flow meter and farm-scale ET measured by a weighing lysimeter. Besides, solar radiation, net radiation, relative humidity and air temperature inside the solar greenhouse were constantly monitored with an automatic weather station at 2.0 m height above ground level. And then the difference of quantitative response of leaf transpiration, plant transpiration and farm-scale ET to the meteorological factors was performed using the path analysis method. Results showed that leaf transpiration rate and stomatal conductance gradually increased with the increase in solar radiation, and reached their maximum values at 10:00-14:00, and then rapidly decreased with solar radiation. Difference in leaf transpiration rate between full irrigation and deficit irrigation appeared at 54-58 days after transplanting. Daily average of leaf transpiration rate in the full irrigation was 10.8% and 14.7% higher than that in deficit irrigation, respectively. Tomato sap flow rate changed with weather conditions, and the difference in plant transpiration between the full irrigation and deficit irrigation was the largest in the sunny day, and the smallest in rainy days, and the plant transpiration was related to solar radiation but lagged behind 1 hour. Daily average of leaf transpiration rate in the full irrigation was 54.8% and 41.2% higher than that in deficit irrigation, respectively in the 2 years. The daily farm-scale ET in the full irrigation and deficit irrigation ranged between 0.32-6.65 mm/d and 0.15-5.91 mm/d, respectively, over the whole growth stage, and the farm-scale evapotranspiration reached the maximum in the full fruit period, accounting for 31.7%-34.7% of the total ET. The path analysis of evapotranspiration at different scales and its controlling meteorological factors indicated that leaf transpiration rate, plant transpiration and farm-scale evapotranspiration could be characterized by the net solar radiation, and the vapor pressure deficit also had significant influence on the scale of individual plant and farmland scale. The influence of wind speed should be considered in estimating plant transpiration rate and farm-scale evapotranspiration. Besides, adding leaf temperature could significantly improve the estimation accuracy of plant transpiration and farm-scale evapotranspiration under the condition of deficit irrigation. This paper provides valuable information for constructing conversion methods and theoretic model at various spatio-temporal scales. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Drought is one of the main environmental stresses for sugarcane. In order to understand the stomatal response of drought stress in different sugarcane cultivars, the present research was conducted using differently drought-resistant sugarcane cultivars F172, GT21, YT93 / 159 and YL6 as plant materials, which were grown in pots in the greenhouse at Guangxi University in 2012. At elongation stage, the plants were treated with varied degrees of drought stress: 1 mild drought, 65%-70% of the soil water capacity; 2 moderate drought, 45%-50% of the soil water content; 3 severe drought with 25%-30% of soil water capacity and; 4 control with 75% of soil water capacity The relative water content in plant leaf was detected, and the. stomatal characteristics in lower epidermis of the plant leaf were observed with scanning electron microscopy. The results showed that the stomatal conductance under water stress declined sharply in 4cultivars. The stomatal conductance in the drought-tolerant F172 and GT21 was lower than that in the drought- susceptible YT93 / 159 and YL6 under severe drought stress. After re-watering in 3 days, the stomatal conductance in F172 and GT21 were increased to 82. 07 and 88. 85 mmol . m-2 . s-1, while that in YT93 / 159 and YL6 was only 18.88 and 33.08mmol . m-2 . s-1, respectively. The water stress resulted in sunken and closed stomata, and reduction in stomata length and width, which showed significant differences in different cultivars. The density of stomata was increased significantly in most drought-tolerant F172 under severe drought stress. The ratio of stomata closure was nearly 3-4 times in F172 and GT21 as much as that in YT93 / 159 and YL6. Under drought stress, the leaf relative water content was reduced. However, the drought-tolerant cultivars F172 and GT21 maintained higher leaf relative water content under severe drought stress than the other two, and YT93 / 159 showed the lowest, and the water content could be restored after re-watering. The results indicated that the drought-resistance of sugarcane cultivars was closely related to the stomatal characteristics and water content in leaf. [ABSTRACT FROM AUTHOR]

The photosynthetic and chlorophyll fluorescence characteristics of 10 Chinese heading cabbage varieties/lines was determined under low temperature to reveal the mechanism of cold resistance of Chinese heading cabbage and guide breeding of Chinese heading cabbage varieties with cold resistance and its out-of-season production. The net photosynthetic rate and stomatal conductance are the highest and the net photosynthetic rate, stomatal conductance and intercellular CO2 concentration of Chinese heading cabbage varieties with bolting tolerance are higher than varieties without bolting tolerance. The net photosynthetic rate and intercellular CO2 concentration of Chinese heading cabbage is affected by stomatal factors. There is no significant difference in maximum photochemistry efficiency ( Fv/Fm) of photosystem II ( PS II) between Chinese heading cabbage varieties with different bolting characteristics. The actual photochemistry efficiency can be used as the auxiliary index to judge its cold resistance due to its consistency with net photosynthetic rate and bolting characteristics. [ABSTRACT FROM AUTHOR]

Under the climatic and ecological conditions of Xingjiang, Northwest China, different degrees of drought stress were installed during the growth stages of cotton, and the drip irrigation with mulch was adopted, aimed to study the effects of drought stress and re-watering on the endogenous hormones (abscisic acid, ABA; and zeatins, ZRs) contents of cotton roots and leaves and the stomatal conductance (gs) of cotton leaves. With the increase of drought stress at different growth stages, the ABA contents of cotton roots and leaves increased, while the ZRs contents of cotton roots and leaves and the gs and photosynthetic rate (Pn) of cotton leaves decreased, with greater decrements in the treatment of soil moisture content being 40% -45% of field capacity at early floweringfull flowering stage. After re-watering, the ABA contents of cotton roots and leaves did not have a decrease with the improvement of soil moisture regime, while the ZRs contents of cotton roots recovered rapidly or exceeded the control after 1-3 days of re-watering. There was a positive correlation between the ZRs contents of cotton roots and the gs of cotton leaves. In the treatment of soil moisture content being 50% -55% of field capacity at full budding-early flowering stage, the ZRs contents and gs of cotton leaves recovered more quickly and with greater increments. It was suggested that the higher ZRs contents of cotton roots after re-watering could be the main cause for the higher stomatal conductance and photosynthetic rate of cotton leaves. [ABSTRACT FROM AUTHOR]

Taking three spring wheat cultivars as test materials, a field experiment was conducted to study the effects of different irrigation treatments on the stomatal conductance of the cultivars during their growth period, with the relationships between the stomatal conductance and the environmental factors analyzed. On the basis of winter irrigation with 1800 m3·hm-2 of water, three irrigation treatments, i.e., irrigating three times (T1), two times (T2), and once (T3) during spring wheat growth period, were installed, with 1050 m3·hm-2 of irrigation water each time. All irrigation treatments had greater effects on the stomatal conductance, which was decreased with the decreasing times of irrigation, and varied with the cultivars. From jointing stage to florescence, the stomatal conductance in all treatments had the same variation trend, i. e., decreased after an initial increase, and reached the peak at heading stage. After florescence, difference occurred among the treatments. In treatment T1, the stomatal conductance of all test cultivars increased after an initial decrease; in treatment T2, the variation patterns of stomatal conductance differed with cultivars; while in treatment T3, the conductance of all cultivars decreased all along. Among the environmental factors, relative atmospheric humidity had the greatest effects on the stomatal conductance, and their correlation coefficient in treatments T2 and T3 reached significant (0.82*)and very significant (0.92**). respectively. The stomatal regulation mechanism of spring wheat adapting to water deficit in Hexi corridor was of feedback manner. [ABSTRACT FROM AUTHOR]

By using FACE system, the microclimate in rice canopy and related physiological indices were observed continuously from the elongation to the maturing stage of rice growth, and the effects of FACE on the rice canopy evapotranspiration and water use efficiency were studied and simulated with energy balance analysis. The results showed that using P-M equation to describe the quantitative relationships of rice leaf stomatal conductance with photosynthetically active radiation (PAR) and vapour pressure deficit (VPD) could better simulate rice canopy evapotranspiraton under FACE and ambient conditions. During observation period, the total water use of rice in FACE plot had a 10 mm decrease, compared with that in control plot. Considering of the 12% increase of total biomass, the water use efficiency of rice under FACE condition was increased by 12%. [ABSTRACT FROM AUTHOR]

Water use efficiency (WUE) is different among species and regions. Few literatures have been reviewed related to long-term WUE of Platycladus orientalis in mountainous areas of Beijing, China. Tree-ring δ 13 C of P. orientalis was used to determine the long-term variation of annual intrinsic water use efficiency (WUE i ) and its response to environmental change. Combining with quantification of tree-ring width, the relationship between net carbon sequestration and WUE i of P. orientalis was eventually explored. The results showed that mean annual temperature increased with the increase of time from 1918 to 2013, whereas annual precipitation fiercely fluctuated. Tree-ring δ 13 C decreased and WUE i increased over time. WUE i was positively related and more sensitive to air temperature increasing than temperature decreasing. Correlation between WUE i and fluctuated annualprecipitation was ambiguous, which indicated the precipitation was not the main factor affecting WUE i . The de-trend tree-ring width of P. orientalis increased initially and then decreased, especially in recent 20 years. According to the correlation between WUE i and environmental factors, temperature resulted in stomatal conductance (g s ) decreasing, which caused a reduction in evapotranspiration and an increase in respiratory loss, leading to the increase of WUE i and a down trend in net carbon sequestration and tree growth.