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1Effect of wind field below unmanned helicopter on droplet deposition distribution of aerial spraying显示文摘Wind field is one of the important factors affecting the distribution characteristics of aerial spraying droplet deposition.In order to reveal the impact mechanism of droplet deposition distribution by the wind field below agricultural unmanned helicopter rotor,in this study,the wind field distribution below uniaxial single-rotor electric unmanned helicopter rotor was measured by using a wireless wind speed sensor network measurement system for unmanned helicopter.The effects of wind field in three directions(X,Y,Z)below the rotor on droplet deposition distribution were analyzed with the condition of aerial spraying droplet deposition in rice canopy,and the regression model was established via variance and regression analyses of experiment results.The results showed that,the wind field in Y direction had a significant effect on droplet deposition in effective spray area,the wind field in Z direction had an extremely significant effect on droplet deposition in effective spray area,and the corresponding significance(sig.)values were 0.011 and 0.000.Furthermore,the wind field in Z direction had a significant effect on the penetrability and uniformity of droplet deposition in effective spray area,the corresponding sig.values were 0.025 and 0.011 respectively.The wind speed in Y direction at the edge of effective spray area had a significant effect on droplet drift,the sig.value was 0.021.In addition,the correlation coefficient R of the regression model was 0.869 between droplet deposition in effective spray area and the wind speed in Y and Z directions,and 0.915 between the uniformity of droplet deposition in effective spray area and the maximum wind speed in Z direction.The result revealed the influencing mechanism of the wind field below the rotor of uniaxial single-rotor electric unmanned helicopter on the distribution of aerial spraying droplet deposition.The results can provide guidance for the actual production application of aerial spraying to reduce liquid drift and improve the utilization rate of pesticide.Chen Shengde Yubin Lan Li Jiyu Zhou Zhiyan Liu Aimin Mao Yuedong 2017International Journal of Agricultural and Biological Engineering2017,10,3:25
2The spring soil moisture and the summer rainfall in eastern China显示文摘The relation between the soil moisture in spring and the rainfall in summer in eastern China is investi- gated. Results show that the summer rainfall in eastern China is closely related to the spring soil moisture in the area from North China to the lower reaches of Yangtze River (NCYR). When spring soil moisture anomalies over NCYR are positive, the summer precipitation exhibits positive anomalies in Northeast China and the lower reaches of Yangtze River, and negative anomalies in southern China and North China. The higher soil moisture over NCYR cools land surface and reduces the land-sea tem- perature gradient, which weakens East Asian summer monsoon. The western Pacific Subtropical High (WPSH) is located to the south and shifts westward, resulting in more rainfall in the lower reaches of Yangtze River and less in southern China and North China.ZUO ZhiYan ZHANG RenHe 2007Chinese Science Bulletin2007,52,23:23
3N-doped defective carbon with trace Co for efficient rechargeable liquid electrolyte-/all-solid-state Zn-air batteries显示文摘Simple synthesis of multifunctional electrocatalysts with plentiful active sites from earth-abundant materials is especially fascinating. Here, N-doped defective carbon with trace Co(1.5 wt%) was prepared via a scalable one pot solid pyrolysis process. The sample exhibits efficient bifunctional OER/ORR activity in alkaline, mainly ascribed to the unique micro-mesoporous structure(1–3 nm), high population of graphitic-N doping(up to 49.0%), abundant defects and the encapsulated Co nanoparticles with graphitized carbon. The according rechargeable liquid Zn-air batteries showed excellent performance(maximum power density of 154.0 mW cm^(-2); energy density of 773 Wh kg^(-1) at 5 mA cm^(-2) and charging-discharging cycling stability over 100 cycles). As a proof-of-concept, the flexible, rechargeable all-solid-state Zn-air batteries were constructed, and displayed a maximum power density as high as 45.9 mW cm^(-2), among the top level of those reported previously.Zhiyan Chen Qichen Wang Xiaobin Zhang Yongpeng Lei Wei Hu Yao Luo Yaobing Wang 2018Science Bulletin2018,63,9:14
4Influence of Soil Moisture in Eastern China on the East Asian Summer Monsoon显示文摘The sensitivity of the East Asian summer monsoon to soil moisture anomalies over China was investigated based on ensembles of seasonal simulations(March–September) using the NCEP GCM coupled with the Simplified Simple Biosphere Model(NCEP GCM/SSi B). After a control experiment with free-running soil moisture, two ensembles were performed in which the soil moisture over the vast region from the lower and middle reaches of the Yangtze River valley to North China(YRNC) was double and half that in the control, with the maximum less than the field capacity. The simulation results showed significant sensitivity of the East Asian summer monsoon to wet soil in YRNC. The wetter soil was associated with increased surface latent heat flux and reduced surface sensible heat flux. In turn, these changes resulted in a wetter and colder local land surface and reduced land–sea temperature gradients, corresponding to a weakened East Asian monsoon circulation in an anomalous anticyclone over southeastern China, and a strengthened East Asian trough southward over Northeast China. Consequently, less precipitation appeared over southeastern China and North China and more rainfall over Northeast China. The weakened monsoon circulation and strengthened East Asian trough was accompanied by the convergence of abnormal northerly and southerly flow over the Yangtze River valley, resulting in more rainfall in this region.In the drier soil experiments, less precipitation appeared over YRNC. The East Asian monsoon circulation seems to show little sensitivity to dry soil anomalies in NCEP GCM/SSi B.Zhiyan ZUO Renhe ZHANG 2016Advances in Atmospheric Sciences2016,33,2:13
5Benzene alkylation with methanol over phosphate modified hierarchical porous ZSM-5 with tailored acidity显示文摘The acidity and acid distribution of hierarchical porous ZSM-5 were tailored via phosphate modification. The catalytic results showed that both benzene conversion and selectivity of toluene and xylene increased with the presence of appropriate amount of phosphorus. Meanwhile, side reactions such as methanol to olefins related with the formation of by-product ethylbenzene formation and isomerization of xylene to meta-xylene were suppressed efficiently. The acid strength and sites amount of Br?nsted acid of the catalyst were crucial for improving benzene conversion and yield of xylene, whereas passivation of external surface acid sites played an important role in breaking thermodynamic equilibrium distribution of xylene isomers.Jinghui Lyu Hualei Hu Carolyn Tait Jiayao Rui Caiyi Lou Qingtao Wang Wenwen Han Qunfeng Zhang Zhiyan Pan Xiaonian Li 2017Chinese Journal of Chemical Engineering2017,25,9:11
6A new-generation sand and dust storm forecasting system GRAPES_CUACE/Dust:Model development,verification and numerical simulation显示文摘Based on the new-generation Global/Regional Assimilation and PrEdiction System(GRAPES) developed by the Numerical Prediction Research Center,China Meteorological Administration and the Chinese Unified Atmospheric Chemistry Environment for Dust Atmospheric Chemistry Module(CUACE/Dust) developed by the Centre for Atmosphere Watch and Services(CAWAS) of the Chinese Academy of Meteorological Sciences(CAMS) ,the China sand and dust storm forecasting system GRAPES /CUACE-Dust model has been established.The latest data of land desertification,optical properties of China sand and dust aerosols,daily soil moisture and snow cover over China main land was introduced in this system.The system showed good performance in mass conservation.The comparisons of real-time prediction outputs with surface observations and aerosol indices derived from TOMS ozone spectrophotometers(TOMS AI) indicate that the model can predict the outbreak,development,transport and depletion processes of sand and dust storms accurately over China and the East Asian region.The system makes real-time quantitative prediction of a series of elements including sand and dust injection from the surface,dry and wet deposition amount,dust concentration and optical depth.We selected 7 major dust storms occurring in April 2006 and analyzed the spatiotemporal distribution patterns of dust emission,dry and wet deposition and atmospheric load in this paper.The results showed that about 225 million tons of dust were emitted into the atmosphere from the deserts over east Asia in that month.The 3 major sand and dust sources were just as the following:The deserts in northern Inner Mongolia and the boundary area around China-Mongolia were the first dust sources with a contribution of 153 million tons accounting for 68%of the total emission.The Taklimakan Desert ranked second and contributed approximately 40 million tons accounting for 17%of the dust emission.The Onqin Daga Sandland emitted about 15 million tons or 7%of the total emission.The contributions from other deserts,sandy lands and abandoned farmlands were about only 8%of the total dust emission.The total deposition over the East Asian region in April 2006 was 136 million tons.The regional distribution of dust deposition showed that the 3 major sources were also the major deposition areas.The deposition amount in the 3 major sources accounted for 78%of the total with about 135 million tons falling back to the source regions.The secondary deposition area was the China mainland downriver,where more than 2 million tons deposited accounting for 16%of the total deposition.The deposition over the region east of 120°E including China off-shore regions,Korean Peninsula,Japan and the West Pacific took only 6%of the total deposition,which was about 850000 tons.The analysis on dry and wet deposition showed that dry deposition dominated in the process,accounting for 94%of the total sand and dust depositions in the period and wet deposition only was around for 6%,since it was generally dry with less rainfall over northern China in April.WANG Hong GONG ShanLing ZHANG HongLiang CHEN Yong SHEN XueShun CHEN DeHui XUE JiShan SHEN YuanFang WU XiangJun JIN ZhiYan 2010Chinese Science Bulletin2010,55,7:10
7Design and test of operation parameters for rice air broadcasting by unmanned aerial vehicle显示文摘Considering the difficulty of broadcasting in the small plots and complex terrain in South China,this research aimed to explore a new efficient broadcasting way and figure out advisable operation parameters by using a hollow 12-axis,rotor-wing Unmanned Aerial Vehicle(UAV)which is typically made up of four groups of solid support structure,with each consisting of three axes and two rotor wings.A 3.7 L reverse pyramid-shape seed hopper with a 60 mm×13 mm rectangular outlet at the bottom was designed to realize self-gravity seeding.Rice seed firstly directly falls on the rotating disc driven by direct-current dynamo before being sown.The disc was located 120 mm above the ground,with a diameter of 350 mm.Under constant flight conditions,parameters of the on-board broadcasting devices(dropping speed referring to speed for the outlet and the broadcasting speed for the disc’s rotation speed)determine the uniformity of air broadcasting.The FUTABA T8FG transmitter and receiver system were employed as the remote control device.When the UAV flies at 3 m/s and 2 m above the ground with an expected seeding of 180 grain/m^(2),the RD(Right Down)knob marked 29 and LD(Left Down)knob marked-24 with a disc rotation speed of 900 r/min,the broadcasting lasts for 15 seconds with a 25%opening(1.95 cm^(2))of rectangular outlet.In order to verify the feasibility of air broadcasting parameters,the project team carried out a field broadcasting test by using a hollow multi-rotor UAV at Zhongluotan Test Base in Guangzhou in July,2014.In the square field plots of 0.09 hm^(2),flying path of air broadcasting operation was designed.The collected sampling data of broadcasting quantity per unit area after the test showed that there were,on average,187.4 grains/m^(2)of the five sampling points with a standard deviation of 22.77,and a coefficient of variation of 12.15%which was far smaller than that of artificial broadcasting.The average yield of field broadcasted by UAV is 7705.5 kg/hm^(2)in 2014,implying that rice air broadcasting by UAV is feasible.Li Jiyu Lan Yubin Zhou Zhiyan Zeng Shan Huang Cong Yao Weixiang Zhang Yang Zhu Qiuyang 2016International Journal of Agricultural and Biological Engineering2016,9,5:10
8Acquisition of deleterious mutations duringpotato polyploidization显示文摘Potatoes(Solanum tuberosum L.) represent an important tuber crop, worldwide. During its prolonged clonal propagation, numerous deleterious mutations have accumulated in the potato genome,leading to severe inbreeding depression; however,the shaping of this mutation burden during polyploidization and improvement is largely unknown.Here, we sequenced 20 diploid landraces of the Stenotomum group, eight tetraploid landraces, and 20 tetraploid modern cultivars, to analyze variations in their deleterious mutations. We show that deleterious mutations accumulated rapidly during the polyploidization of tetraploid potatoes. This study provides a foundation for future potato improvement.Qun Lian Die Tang Zhiyan Bai Jianjian Qi Fei Lu Sanwen Huang Chunzhi Zhang 2019Journal of Integrative Plant Biology2019,61,1:8
9Analysis and Calculation for Heating and Temperature Rise of Magnetic Levitation Device显示文摘准确的热分析是磁悬浮系统电磁装置优化设计、防止过热的前提。提出了基于等效热路模型的电磁装置发热及温升计算方法,并与基于"场"的仿真分析结果进行比较,验证其正确性。首先,利用ANSYS软件建立电磁装置的瞬态温度场模型,并将装置中动铁心随大轴旋转时与空气产生的风摩擦损耗包含在模型中,通过仿真分析,得到电磁装置温度分布;然后,通过对散热路径的分析建立了电磁装置的等效热路模型,从"路"的角度计算出本电磁装置各位置的温升;最后,将基于"路"的计算结果与基于"场"的仿真结果进行了比较分析,各部分温升误差均在允许范围内,验证了等效热路模型计算电磁装置发热及温升方法的准确性和可行性。在基于"场"和"路"的两种分析中,均考虑了电阻率随温升的变化,散热分析中均计及了导热系数和对流散热系数随温度的变化。MA Hongzhong GENG Zhihui WANG Qingyan ZHANG Zhiyan 2012中国电机工程学报2012,32,30:7
10Optimization of variables for maximizing efficacy and efficiency in aerial spray application to cotton using unmanned aerial systems显示文摘Aerial spraying can support efficient defoliation without crop contact.With the recent introduction to unmanned aerial system(UAS)for aerial spraying in China,there is a need to determine the optimum application variables to achieve high efficacy and efficiency with low costs.The present research involved field studies across two annual cotton production seasons in North Xinjiang,China.Four factors,including volume rate(A),tank mix including spray adjuvants(B),flight altitude(C),flight speed(D)and three levels of L9(3^(4))orthogonal arrays were carried out to optimize the application parameters for three types of UASs.These included different numbers of rotors as follows:four-rotors,six-rotors and eight-rotors.Spray coverage,distribution uniformity(coefficient of variation(CV)of droplet coverage),rates of cotton defoliation and boll opening,application efficiency and cost were measured and assessed.Results showed that:(1)the rates of defoliation and boll opening by aerial cotton defoliant application could meet the requirement of cotton mechanized harvesting;(2)the optimal scenario for the three UASs was A_(3)B_(2)C_(1)D_(3),Volume rate(A3):48 L/hm^(2);Tank mix and concentration(B_(2)):(Tuotulong 225+Sujie 750+Ethephon 2250)mL/hm^(2),Flight altitude(C_(1)):1.5 m,and Flight speeds(D_(3))for unmanned helicopters with four-rotors,six-rotors and eight-rotors were 3.12 m/s,2.51 m/s and 3.76 m/s,respectively.These results can provide guidance for cotton defoliant aerial spraying in China using UAS.Juan Liao Ying Zang Xiwen Luo Zhiyan Zhou Yubin Lan Yu Zang Xiuyan Gu Weiming Xu Andrew John Hewitt 2019International Journal of Agricultural and Biological Engineering2019,12,2:6
11Review of Chinese atmospheric science research over the past 70 years: Climate and climate change显示文摘Climate and climate change have always been a research focus of atmospheric sciences. This paper summaries research efforts, achievements and international contributions of the Chinese scientific community on climate and climate change over the past 70 years. The review is based on papers published officially in national or international scientific journals,and is organized to cover six aspects:(1) general climate studies;(2) impact of the Qinghai-Tibetan Plateau;(3) impact of the East Asian monsoon;(4) influences of teleconnection oscillation and westerlies;(5) climate dynamics and development of climate models;and(6) climate change. It is, however, to be noted that the present review can not be considered as an exhaustive one, since there is a huge body of literature in the field.Jianping HUANG Wen CHEN Zhiping WEN Guangjun ZHANG Zhaoxin LI Zhiyan ZUO Qingyun ZHAO 2019Science China Earth Sciences2019,62,10:6
12Novel algorithm for constructing support vector machine regression ensemble显示文摘A novel algorithm for constructing support vector machine regression ensemble is proposed. As to regression prediction, support vector machine regression (SVMR) ensemble is proposed by resampling from given training data sets repeatedly and aggregating several independent SVMRs, each of which is trained to use a replicated training set. After training, several independently trained SVMRs need to be aggregated in an appropriate combination manner. Generally, the linear weighting is usually used like expert weighting score in Boosting Regression and it is without optimization capacity. Three combination techniques are proposed, including simple arithmetic mean,linear least square error weighting and nonlinear hierarchical combining that uses another upper-layer SVMR to combine several lower-layer SVMRs. Finally, simulation experiments demonstrate the accuracy and validity of the presented algorithm.Li Bo Li Xinjun Zhao Zhiyan 2006Journal of Systems Engineering and Electronics2006,17,3:6
13Integrated sensor system for monitoring rice growth conditions based on unmanned ground vehicle system显示文摘Ground-based platform systems provide a good tool for monitoring and managing crop conditions in precision agriculture applications and have been widely used for monitoring crop conditions.To develop an unmanned ground vehicle system(UGVS)based multi-sensors and test the feasibility of this system for monitoring rice conditions,an UGVS was developed to collect real-time rice condition information including NDVI values,reflectance measurements and crop canopy temperature in this study.Major components of the integrated system are GreenSeeker R100 system,hyper-spectroradiometer and infrared temperature sensor.The leaf area index(LAI)was measured by the CGMD302 Spectrometer.The Independent Samples T-Test method and the one way ANOVA method were used to determine the best spectral indices and analyze the relationship between the vegetation indices and rice LAI.It was found that the two best spectral indices for estimating LAI were NDVI(860 nm and 750 nm)with the correlation coefficient(R^(2))at 0.745 and RVI(853 nm and 751 nm)with the R^(2)at 0.724.The results show the UGVS can support multi-source information acquisition and is useful for crop management and precision agriculture applications.Wang Pei Yubin Lan Luo Xiwen Zhou Zhiyan Zhigang Wang Yonghui Wang 2014International Journal of Agricultural and Biological Engineering2014,7,2:6
14Facile grafting strategy synthesis of single-atom electrocatalyst with enhanced ORR performance显示文摘Single-atom catalysts(SACs)have become one of the most considered research directions today,owing to their maximum atom utilization and simple structures,to investigate structure-activity relationships.In the field of non-precious-metal electrocatalysts,atomically dispersed Fe-N4 active sites have been proven to possess the best oxygen reduction activity.Yet the majority of preparation methods remains complex and costly with unsatisfying controllability.Herein,we have designed a surface-grafting strategy to directly synthesize an atomically dispersed Fe-NVC electrocatalyst applied to the oxygen reduction reaction(ORR).Through an esterification process in organic solution,metal-containing precursors were anchored on the surface of carbon substrates.The covalent bonding effect could suppress the formation of aggregated particles during heat treatment.Melamine was further introduced as both a cost-effective nitrogen resource and blocking agent retarding the migration of metal atoms.The optimized catalyst has proven to have abundant atomically dispersed Fe-N4 active sites with enhanced ORR catalytic performance in acid condition.This method has provided new feasible ideas for the synthesis of SACs.Rui Ding Yide Liu Zhiyan Rui Jia Li Jianguo Liu Zhigang Zou 2020Nano Research2020,13,6:6
15Dynamic Uplink Transmission Scheduling for Satellite Internet of Things Applications显示文摘Satellite communication systems provide a cost-effective solution for global internet of things(IoT)applications due to its large coverage and easy deployment.This paper mainly focuses on Satellite networks system,in which low earth orbit(LEO)satellites network collect sensing data from the user terminals(UTs)and then forward the data to ground station through geostationary earth orbit(GEO)satellites network.Considering the limited uplink transmission resources,this paper optimizes the uplink transmission scheduling scheme over LEO satellites.A novel transmission scheduling algorithm,which combined Algorithms of Simulated Annealing and Monte Carlo(SA-MC),is proposed to achieve the dynamic optimal scheduling scheme.Simulation results show the effectiveness of the proposed SA-MC algorithm in terms of cost value reduction and fast convergence.Li Wang Shuaijun Liu Weidong Wang Zhiyan Fan 2020China Communications2020,17,10:6
16Inter-decadal variations of springtime rainfall over southern China mainland for 1979-2004 and its relationship with Eurasian snow显示文摘This study analyzes the inter-decadal variations of rainfall over southern China in spring (March-April-May) using the observed precipitation data for 1979-2004. The result shows that the variations of spring rainfall over southeastern China are opposite to those over and southwestern China in both inter-annual and inter-decadal time scales. The precipitation over south- ern China exhibits an apparent inter-decadal shift in the late 1980s. The accumulated spring rainfall has reduced 30% over southeastern China after the late 1980s, whereas it has increased twice as much over southwestern China. The atmospheric circulations related to this shift show that an abnormal high at lower and middle troposphere appears over Asian middle and high latitudes, accompanied by stronger-than-normal northerly wind over eastern China. Consequently, the wet air flows from tropical oceans are weakened over southern China, resulting in less rainfall over southeastern China and more rainfall over southwestern China. Furthermore, the anomalous atmospheric circulation over Asian middle and high latitudes is closely related to the inter-decadal downward shift of Eurasian spring snow in the late 1980s, indicating that the inter-decadal shift of Eurasian spring snow in the late 1980s is probably an important factor in the decadal shift of spring rainfall over southern China.ZUO ZhiYan ZHANG RenHe WU BingYi 2012Science China Earth Sciences2012,55,2:5
17Velocity-dependent symmetries and non-Noether conserved quantities of electromechanical systems显示文摘The theory of velocity-dependent symmetries(or Lie symmetry) and non-Noether conserved quantities are presented corresponding to both the continuous and discrete electromechanical systems.Firstly,based on the invariance of Lagrange-Maxwell equations under infinitesimal transformations with respect to generalized coordinates and generalized charge quantities,the definition and the determining equations of velocity-dependent symmetry are obtained for continuous electromechanical systems;the Lie's theorem and the non-Noether conserved quantity of this symmetry are produced associated with continuous electromechanical systems.Secondly,the operators of transformation and the operators of differentiation are introduced in the space of discrete variables;a series of commuting relations of discrete vector operators are defined.Thirdly,based on the invariance of discrete Lagrange-Maxwell equations under infinitesimal transformations with respect to generalized coordinates and generalized charge quantities,the definition and the determining equations of velocity-dependent symmetry are obtained associated with discrete electromechanical systems;the Lie's theorem and the non-Noether conserved quantity are proved for the discrete electromechanical systems.This paper has shown that the discrete analogue of conserved quantity can be directly demonstrated by the commuting relation of discrete vector operators.Finally,an example is discussed to illustrate the results.FU JingLi CHEN BenYong FU Hao ZHAO GangLing LIU RongWan ZHU ZhiYan 2011Science China(Physics,Mechanics & Astronomy)2011,54,2:4
18152 W high-power blue diode laser operated at 447 nm显示文摘We demonstrate a high-power blue diode laser operated at 447 nm combining laser diodes using an optical fiber bundle. As many as 127 diode lasers at 447 nm were coupled into 400 μm/0.22 NA fibers using an aspherical lens group with different focus lengths. The bare fibers were mechanically bundled through high temperature ultraviolet adhesive after the coatings of the 127 fibers were stripped. The diameter of the fiber bundle was 6 mm. The total output power of such a bundle was 152 W with electro-optical conversion efficiency of 27.56%and the RMS power instability was less than ±1% within 3 h.Peng Wu Ling Zhang Haijuan Yu Xiandan Yuan Zhiyan Zhang Pengfei Zhao Shuzhen Zou Chaojian He Yaoyao Qi Yingying Yang Gang Li Xubao Wang Xuechun Lin 2017Journal of Semiconductors2017,38,7:4
19Novel benzamido derivatives as PTP1B inhibitors with anti-hyperglycemic and lipid-lowering efficacy显示文摘Based on a non-competitive and selective PTP1 B inhibitor reported by us previously, thirtynine benzamido derivatives were designed and synthesized as novel PTP1 B inhibitors. Among them,twelve compounds exhibited IC_(50) values at micromolar level against human recombinant PTP1 B, and most of them exhibited significant selectivity to PTP1 B over TC-PTP and CD45. Further evaluation of the most potent compound 27 on high-fat diet(HFD)-induced insulin-resistant(IR) obese mice indicated that27 could modulate glucose metabolism and ameliorate dyslipidemia simultaneously.& 2018 Chinese Pharmaceutical Association and Institute of Materia Medica, Chinese Academy of Medical Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license(http://creativecommons.org/licenses/by-nc-nd/4.0/).Yanbo Tang Xiaolin Zhang Zheng Chen Wenwen Yin Guanglei Nan Jinying Tian Fei Ye Zhiyan Xiao 2018Acta Pharmaceutica Sinica B2018,8,6:4
20The mechanism underlying overwintering death in poplar:the cumulative effect of effective freeze-thaw damage显示文摘We analyzed the relationships linking overwintering death and frost cracking to temperature and sunlight as well as the effects of low temperatures and freeze–thaw cycles on bud-burst rates,relative electrical conductivity,and phloem and cambial ultrastructures of poplar.Overwintering death rates of poplar were not correlated with negative accumulated temperature or winter minimum temperature.Freeze–thaw cycles caused more bud damage than constant exposure to low temperatures.Resistance to freeze–thaw cycles differed among clones,and the budburst rate decreased with increasing exposure to freeze–thaw cycles.Cold-resistant clones had the lowest relative electrical conductivity.Chloroplasts exhibited the fastest and the most obvious reaction to freeze–thaw damage,whereas a single freeze–thaw cycle caused little damage to cambium ultrastructure.Several such cycles resulted in damage to plasma membranes,severe damage to organelles,dehydration of cells and cell death.We conclude that overwintering death of poplar is mainly attributed to the accumulation of effective freeze–thaw damage beyond the limits of freeze–thaw resistance.Chengchao Yang Jiandong Peng Xiaoyu Li Dejun Liang Zhiyan Yang Yan Zhang 2020Journal of Forestry Research2020,31,1:4
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