Effects of short-term osmotic stress on leaf hydraulic conductivity and ZmPIPs mRNA accumulation in maize seedlings

Plants maintain water balance by varying hydraulic properties, and plasma membrane intrinsic proteins（PIPs） may be involved in this process. Leaf xylem and root hydraulic conductivity and the m RNA contents of four highly expressed Zm PIP genes（Zm PIP1;1, Zm PIP1;2, Zm PIP2;2, and Zm PIP2;5） in maize（Zea mays） seedlings were investigated. Under well-watered conditions, leaf hydraulic conductivity（K_（leaf）） varied diurnally and was correlated with whole-plant hydraulic conductivity. Similar diurnal rhythms of leaf transpiration rate（E）, K_（leaf） and root hydraulic conductivity（K_（root）） in well-watered plants are important for maintaining whole-plant water balance. After 2 h of osmotic stress treatment induced by 10% polyethylene glycol 6000, the K_（root） of stressed plants decreased but K_（leaf） increased, compared with well-watered plants. The m RNA contents of four Zm PIPs were significantly up-regulated in the leaves of stressed plants, especially for Zm PIP1;2. Meanwhile, Zm PIP2;5 was significantly down-regulated in the roots of stressed plants. After 4 h of osmotic stress treatment, the E and leaf xylem water potentials of stressed plants unexpectedly increased. The increase in K_（leaf） and a partial recovery of K_（root） may have contributed to this process. The m RNA content of Zm PIP1;2 but not of the other three genes was up-regulated in roots at this time. In summary, the m RNA contents of these four Zm PIPs associated with K_（leaf） and K_（root） change in maize seedlings during short-term osmotic stress, especially for Zm PIP1;2 and Zm PIP2;5, which may help to further reveal the hydraulic resistance adjustment role of Zm PIPs.

A new apparatus for investigating stress,deformation and seepage coupling properties of rock fractures

A true triaxial apparatus which is composed of three units was presented.The apparatus allows for investigations on deformation and seepage behaviors of a single rock fracture subjected to lateral stress and normal stress.The first unit has three jacks which can apply loads independently in three orthogonal directions.The second unit is used to supply water inflow,control seepage pressure and measure flow velocity in real time.The third unit is for measuring the normal deformation of rock fractures.Some tests for investigating the normal deformation and seepage behaviors of rock fractures subjected to normal and lateral loads on hard granite specimens with an artificial persistent fracture,were introduced.The results show that both the normal deformation and the hydraulic conductivity are influenced not only by the normal stress but also by the lateral stress.It is also shown that the aperture and the hydraulic conductivity decrease with the increasing normal stress but increase with the increasing lateral stress and both the aperture and the hydraulic conductivity obey exponential relationships with the normal stress and the lateral stress.

Theory and application of rock burst prevention using deep hole high pressure hydraulic fracturing

In order to analyze the mechanism of deep hole high pressure hydraulic fracturing, nonlinear dynamic theory, damage mechanics, elastic-plastic mechanics are used, and the law of crack propagation and stress transfer under two deep hole hydraulic fracturing in tectonic stress areas is studied using seepage-stress coupling models with RFPA simulation software. In addition, the effects of rock burst control are tested using multiple methods, either in the stress field or in the energy field. The research findings show that with two deep holes hydraulic fracturing in tectonic stress areas, the direction of the main crack propagation under shear-tensile stress is parallel to the greatest principal stress direction. High-pressure hydraulic fracturing water seepage can result in the destruction of the coal structure, while also weakening the physical and mechanical properties of coal and rock. Therefore the impact of high stress concentration in hazardous areas will level off, which has an effect on rock burst prevention and control in the region.

Flow of couple stress fluid with variable thermal conductivity

The steady flow and heat transfer of a couple stress fluid due to an inclined stretching cylinder are analyzed. The thermal conductivity is assumed to be temperature dependent. The governing equations for the flow and heat transfer are transformed into ordinary differential equations. Series solutions of the resulting problem are computed. The effects of various interested parameters, e.g., the couple stress parameter, the angle of inclination, the mixed convection parameter, the Prandtl number, the Reynolds number, the radiation parameter, and the variable thermal conductivity parameter, are illustrated. The skin friction coefficient and the local Nusselt number are computed and analyzed. It is observed that the heat transfer rate at the surface increases while the velocity and the shear stress decrease when the couple stress parameter and the Reynolds number increase. The temperature increases when the Reynolds number increases.

Revisiting the methods of determining hydraulic conductivity of saturated expansive clays in low-compressibility zone

The hydraulic conductivity of saturated clays is commonly determined either directly by monitoring water flux or indirectly based on Terzaghi’s consolidation equation.Similar results are generally obtained from the two methods,but sometimes a significant difference can be observed,in particular for expansive soils.In this study,the hydraulic conductivities determined by the two methods are first compared based on existing data in the literature.The indirect method is then revisited attempting to explain the difference identified.A modified effective stress,considering physico-chemical interaction between face-to-face oriented particles,is finally introduced to better describe the compressibility of expansive clays and to further improve the indirect method in determining hydraulic conductivity of such soils in the low-compressibility zone.Extra tests were performed on Gaomiaozi(GMZ)bentonite slurry and the results obtained allowed the modified indirect method to be verified.

Experimental study and modeling of hydromechanical behavior of concrete fracture

In this study, the hydromechanical behavior of a concrete fracture under coupled compressive and shear stresses was investigated. A special experimental device was designed to create a planar fracture in a cylindrical sample and to carry out different kinds of hydromechanical tests on the fracture. Four series of laboratory tests were performed on an ordinary concrete sample. Hydrostatic compression tests were first conducted to characterize the normal compressibility of the fracture. In the second series, direct shear tests were conducted on the fracture under different normal stresses. The maximal shear stress of the fracture was determined as a function of the normal stress. In the third series, fluid flow tests were carried out in view of characterizing the overall hydraulic conductivity of the fracture as a function of its opening and closure. Shear tests with a constant fluid pressure were finally performed to investigate the influence of fluid pressure on the deformation behavior of concrete fractures. Based on the experimental investigation, an elastoplastic model is proposed. This model takes into account the nonlinear elastic behavior of a fracture under normal compression and the plastic deformation and failure due to shear stress. The model was coupled with the classical Darcy's law to describe the fluid flow along the fracture by considering the variation of permeability with fracture aperture. Numerical results agree with experimental data from various laboratory tests.

The effects of soil moisture and salinity as functions of groundwater depth on wheat growth and yield in coastal saline soils

In the coastal saline soils,moisture and salinity are the functions of groundwater depth affecting crop growth and yield.Accordingly,the objectives of this study were to:1)investigate the combined effects of moisture and salinity stresses on wheat growth as affected by groundwater depth,and 2)find the optimal groundwater depth for wheat growth in coastal saline soils.The groundwater depths(0.7,1.1,1.5,1.9,2.3,and 2.7 m during 2013-2014(Y1)and 0.6,1.0,1.4,1.8,2.2,and 2.6 m during 2014-2015(Y2))of the field experiment were maintained by soil columns.There was a positive correlation between soil moisture and salinity.Water logging with high salinity(groundwater depth at 0.7 m in Y1 and 0.6 m in Y2)showed a greater decline towards wheat growth than that of slight drought with medium(2.3 m in Y1)or low salinity(2.7 m in Y1,2.2 and 2.6 m in Y2).The booting stage was the most sensitive stage of wheat crop under moisture and salinity stresses.Data showed the most optimal rate of photosynthesis,grain yield,and flour quality were obtained under the groundwater depth(ditch depth)of 1.9 m(standard soil moisture with medium salinity)and 2.3 m(slight drought with medium salinity)in Y1 and 1.8 m(standard soil moisture with medium salinity)and 2.2 m(slight drought with low salinity)in Y2.The corresponding optimal soil relative moisture content and conductivity with the 1:5 distilled water/soil dilution,in the depth of 0-20 cm and 20-40 cm in coastal saline soils,were equal to 58.67-63.07%and 65.51-72.66%in Y1,63.09-66.70%and 69.75-74.72%in Y2;0.86-1.01 dS m^-1 and 0.63-0.77 dS m^-1 in Y1,0.57-0.93 dS m^-1 and 0.40-0.63 dS m^-1 in Y2,respectively.

Consolidation and Creep Behaviors of Two Typical Marine Clays in China

This paper presents an experimental investigation into the deformation characteristics of two typical marine clays obtained from Dalian and Shanghai, respectively, in China. Three kinds of laboratory tests, i.e. conventional oedometer tests, one-dimensional and triaxial creep tests were carried out. The results obtained from consolidation tests demonstrate linear e−logσv relationships for Shanghai clay at normally consolidated state, while partly or even global non-linear relationships for Dalian clay. The compression index Cc for both clays follows the correlation of Cc = 0.009(wL −10) where wL is the liquid limit of soil. The relationship between logkv (kv is the hydraulic conductivity of soil) and void ratio e is generally linear and the hydraulic conductivity change index Ckv can be described by their initial void ratio for both clays. The secondary compressibility of Dalian clay lies in medium to high range and is higher than that of Shanghai clay which lies in the range of low to medium. Furthermore, based on drained triaxial creep tests, the stress-strain-time relationships following Mesri’s creep equation have been developed for Dalian and Shanghai clays which can predict the long-term deformation of both clays reasonably well.

土壤冻融过程中的水热参数化方案研究进展

冻土是陆地冰冻圈的重要组成部分,其冻融循环变化能够影响土壤结构、土壤水热传输以及土壤生物化学等过程,并通过陆-气相互作用影响局地甚至全球天气气候。因此,研究土壤冻融过程对冻土区人类生产生活和了解区域外天气气候变化具有重要的科学意义。本文回顾了土壤中的砾石、有机质对土壤冻融过程的影响及物理机制,总结了土壤冻融过程中水热参数化的相关研究成果,包括土壤导热率和水力学参数的计算、水热耦合方案以及冻融锋面计算方案等。相对于普通的矿物质土粒而言,砾石具有高导热率和低热容,有机质具有低导热率和高热容,他们对热量在土壤中的传输及土壤温度垂直分布有不同的影响。另外,砾石和有机质的存在改变了土壤孔隙度、土壤基质毛细作用与吸附作用,进而影响水分在土壤中的传输过程和垂直分布。已有研究表明:(1)当前大部分数值模式中土壤导热率采用Johansen方案及其派生方案进行计算,其中Balland-Arp方案考虑了砾石和有机质对土壤导热率的影响,该方案更好地刻画了土壤冻融过程中土壤导热率变化的连续性;综合考虑热-水-变形相互作用的导热率参数化方案可以较好地刻画土壤冻融过程中的水热耦合和土体冻胀的作用,对相变过程中土壤导热率变化特征的模拟更符合实际观测。(2)过冷水参数化方案刻画了土壤液态水在0℃以下存在的事实;相变温度方案描述了土壤相变温度低于0℃且不固定的事实;导水阻抗方案考虑了土壤冻结对土壤水分下渗的阻抗作用,改善了对冻土区水文过程的模拟效果。(3)土壤冻融过程伴随着水分的相变和能量的转化,水热耦合方案的发展能够较好地刻画土壤中热力-水文过程的协同变化特征,细化了对冻融过程中水分和能量相互作用的复杂物理机制的描述。(4)等温框架的数值模式通过模拟每层土壤中间深度的冻融过程代表该模式分层的整体特征,导致对冻融深度的严重高估或低估,尤其是对厚度较大的模式深层土壤,冻融锋面计算方案的提出和应用减小了这种模拟偏差。目前土壤冻融参数化方案的不足之处包括:绝大多数数值模式没有考虑土壤盐分导致土壤水的冰点降低这一事实;虽然大部分数值模式考虑了土壤有机质对土壤水、热传输的影响,但是模式中对土壤有机质含量及垂直分布的考虑与植被根系的生长状态脱节;模式模拟的土壤深度不足并且下边界通量为零的假定不符合实际情况。发展土壤溶质传输参数化方案以模拟盐分的分布、刻画植被根系生长过程和土壤有机质的分布特征、考虑深层土壤对浅层的热力学影响并完善数值模式中的下边界条件,这些是未来陆面模式改进土壤冻融过程模拟的可能方向。

Coupling analysis of unsteady seepage and stress fields in discrete fractures network of rock mass in dam foundation

The drag force of water flow through single fracture and the coupling characteristics of seepage and stress in single fracture surface are analyzed,and a three dimensional model of coupled unsteady seepage and stress fields is proposed.This model is used to the analysis of foundation rock mass of a high dam.If the coupling effects are considered,the changes of boundary heads have less influence on the inner head of rock mass,and the strong permeability of main fractures appears.If the coupling effects are not considered,the fractures distribution affects the inner head more greatly.When the upstream water head declines,the inner head of dam foundation slightly declines and the hydraulic gradient distribution becomes smoother.A bigger upstream water level declining velocity has a stronger lag effect,meanwhile the values of stress components change more greatly.Therefore the upstream water level declining velocity directly affects the stability of rock mass in dam foundation and we should take into account the above factors to make sure the safety of the dam during reservoir level fluctuation period.

基于双重介质渗流-应力耦合模型的高压压水试验渗透参数反演

高压压水试验过程中岩体易发生水力劈裂产生裂隙,岩体内部孔隙、裂隙双重导水,渗流场和应力场相互作用,导致岩体渗透参数的时空变异性。基于高压压水试验反演渗透参数需考虑双重介质渗流-应力耦合作用下产生裂隙前后渗透系数的变化规律,利用渗流-应力耦合数值模型结合工程现场高压压水试验数据进行参数反演,计算得到不同压力阶段下灰岩岩体渗透率。主要结论如下:发生水力劈裂前,随着注液压力的增大,渗透率及孔隙水压力在不同压力阶段之间分界明显,渗透率反演值与规程公式计算值相近;发生水力劈裂后,岩体渗透率增大约2倍,孔隙介质渗透率和通过的流量出现陡减现象。

水力耦合下煤样声发射分形−渗透率模型及试验研究

煤样轴向应力加载-水压渗流作用下裂隙(孔隙)发展直接影响煤样试件的力学指标与渗流特性,文中通过理论解析与力学试验方法,分析了煤样试件裂隙(孔隙)主导下渗透率与声发射分形维数、振铃计数响应关系,建立了水力耦合作用下煤样声发射分形-渗透率模型,开展了不同围压(2~5 MPa,Δpw(渗透压)/p'c(围压)=0.75)下水力耦合煤样渗流试验,分析了不同围压(水压)下煤样试件的力学行为、声发射规律与渗流特征,探讨了不同围压下煤样试件的强度提升特点与破坏形态-声发射定位关系,验证了水力耦合下煤样试件的声发射分形-渗透率模型合理性。结果表明:煤样试件渗流试验中裂隙(孔隙)变化与声发射振铃具有一致性,裂隙(孔隙)扩展与声发射分形维数、渗透率密切相关,声发射分形、渗透率可用体积应变表征,基于声发射分形的水力耦合下煤样试件的声发射分形-渗透率模型可采用2段式数学模型解析;煤样渗流全应力-应变过程中渗透率表现为短时减少—长时缓慢增加—急速增加—小幅回落过程,振铃计数呈快速增加—减少—增加—减少波浪型发展,渗透率最小值滞后体积应变压缩与膨胀临界点,最小渗透率变化在0.124×10^(-17)~1.250×10^(-17)m^(2);随着围压(2~5 MPa)增加,煤样峰值偏应力、峰值轴向应变与峰值体积应变均呈增大趋势,线性特征显著,煤样峰值渗透率滞后峰值强度呈减小趋势,减幅达到93.34%,最大声发射振铃计数(对应峰值强度位置)表现为增加趋势;水力耦合下煤样试件有效黏聚力和有效内摩擦角分别提高到6.5116 MPa与36.56º,随着围压(2~5 MPa)增加,煤样试件的声发射信息由单斜面向不规整斜面过渡,主控破裂面角度由小角度向高角度转变,失稳由单块体剪切变为多块体压缩形态,试件破裂可采用声发射定位振铃计数表达;煤样试件声发射分形-体积应变、渗透率与体积应变、分形与渗透率3个试验曲线与理论曲线较为吻合,围压2~5 MPa试件压缩阶段相关性分别在0.882~0.999、0.950~0.998与0.849~0.997,围压2~5 MPa试件膨胀阶段相关性0.937~0.996、0.891~0.998与0.873~0.966。

航空发动机液压弯管流固耦合振动特性分析

为研究流固耦合作用下多弯曲段液压管道的流体流动与管道振动之间的动力学特性,基于ANSYS Workbench平台分析了航空发动机某易故障部位弯形液压管道的预应力模态,通过SST k-ω湍流模型模拟计算不同流体流速下弯形液压管内流体的流动状态,获得了不同管内流体流速与管道形变以及等效应力之间的关系,得出在允许最大流速下弯管的形变随曲率半径的变化趋势,并总结出该液压弯管不同充液状态下的前六阶固有频率的变化趋势。结果表明:管道形变随流体流速的增加而增大,随曲率半径的增大而减小;弯管不同充液状态下管道的前六阶固有频率随阶数增加而增长且同阶下空管的固有频率大于充液弯管的固有频率;最后通过充液弯管的前六阶振型图分析了不同阶频率易发生形变的部位研究,可为航空发动机弯形液压管道的设计提供参考。

干旱胁迫对甘草幼苗光合特性及根系吸水的影响

甘草(Glycyrrhiza uralensis)为豆科甘草属多年生草本植物,具有极高的药用价值,是我国干旱、半干旱地区重要的经济和生态作物。土壤水分是限制甘草生长的主要环境因素之一,研究其抗旱适应性表现对甘草资源可持续利用具有重要意义。本研究采用聚乙二醇6000(PEG-6000)模拟干旱胁迫,研究胀果甘草(G.inflata)和乌拉尔甘草(G.uralensis)幼苗的光合特性和根系吸水能力对干旱胁迫的响应。结果表明:干旱胁迫7 d后胀果甘草和乌拉尔甘草幼苗地上部干重和根系干重均显著降低,其中地上部干重分别降低56.10%、62.50%,地下部干重分别降低16.67%和28.57%,而根冠比均有所增加。干旱胁迫均造成了胀果甘草和乌拉尔甘草幼苗叶片净光合速率(P_(n))、蒸腾速率(T_(r))和气孔导度(G_(s))的降低,与对照相比,其下降幅度分别为41.73%、67.22%,62.21%、75.38%,66.02%、82.60%。干旱胁迫下甘草幼苗荧光特性也被显著抑制(P<0.05),其中胀果甘草幼苗的光系统Ⅱ潜在活性(F_(v)/F_(o))和最大光能转换效率(F_(v)/F_(m))与对照相比分别降低21.94%和9.09%,乌拉尔甘草幼苗的F_(v)/F_(o)和F_(v)/F_(m)与对照相比分别降低35.10%和10.39%;胀果甘草和乌拉尔甘草幼苗的光化学淬灭系数(qP)在15%PEG胁迫下分别降低17.65%和27.27%。干旱胁迫降低了两种甘草幼苗叶片相对含水量和叶水势,其中胀果甘草幼苗叶片相对含水量降低11.07%,叶水势降低19.54%;乌拉尔甘草幼苗叶片相对含水量降低13.91%,叶水势降低62.56%。干旱胁迫抑制了两种甘草的根系生长,根表面积和根体积减少但增加了总根长,其中胀果甘草根系显著小于乌拉尔甘草,但胀果甘草干旱胁迫下整株根系水力学导度降幅小于乌拉尔甘草。说明在受到干旱胁迫时,胀果甘草可以保持较高的光合作用优势,同时其根系较小具有更高的根系效率,通过更强的根系吸水能力提高了作物水分利用效率,具有更强的抗旱能力。本研究可为补充完善甘草耐旱性理论提供依据,并为人工栽培及旱生植物资源保护与利用提供策略。

干热岩柔性压裂裂缝起裂与扩展规律

考虑岩石热孔隙弹性效应、循环载荷下岩石强度疲劳劣化本构关系、弹脆性破坏准则和井筒应力叠加效应,建立并验证了热流固-疲劳损伤耦合的干热岩柔性水力压裂裂缝扩展数值模型,在此基础上开展数值模拟研究,探究不同温度和循环载荷共同作用下干热岩裂缝起裂及扩展特征。研究表明:①周期注入、流体渗透、孔隙压力累积与岩石强度劣化共同引发柔性压裂岩石疲劳破坏;②干热岩柔性压裂裂缝扩展模式由温差和循环载荷共同控制,温差越大,热应力越强,利于形成复杂缝网;循环载荷降低,热应力波及范围增大,循环载荷为90%pb和80%pb(pb为常规水力压裂时岩石破裂压力)时,改造面积相较于常规水力压裂分别提升88.33%和120%(注入温度为25℃);③随着循环载荷的进一步降低,储层改造效果减弱,循环载荷降低至70%pb时,距离井筒较远处流体压力无法达到岩石最低破裂压力,不会产生宏观水力裂缝。

水力压裂延迟活化断层的多场耦合数值模拟研究——以加拿大福克斯溪地区诱发地震为例

加拿大西部盆地的福克斯溪(Fox Creek)页岩气开采区自压裂开采以来,地震频度急剧增加,引发工业界和科学界的广泛关注。目前一些典型诱发地震案例的断层活化动力学机制尚未完全厘清。本文以2014年初福克斯溪地区Duvernay地层附近发生的地震群及构造为研究对象,开展地下断层受流体扰动而活化的多场耦合数值模拟研究。文中重点讨论的1号平台附近发生的诱发地震主要沿着两个较为清晰的发震断层发生,最大震级M_(W)3.9事件发生于压裂井下方约1 km处的结晶基底内,并具有典型的延迟触发特点。本文就上述断层的滞后活化现象开展数值模拟研究。首先,基于PKN裂缝扩展模型计算并验证注入流体的应力扰动输入项,根据地震数据识别出断层的具体位置,结合地层和构造信息建立二维地质模型;然后,耦合固体力学、流体渗流定律和断层活化理论搭建多孔弹性介质内的断层活化数值仿真模型;最后,采用有限元方法数值模拟水力压裂活化断层的全过程,通过计算库仑应力改变量(ΔCFS)的值来观测断层活化前后的流固耦合场和应力应变场的演化特征。结果表明,经过5天注水和15天扩散的流体作用,西断层附近的ΔCFS持续增加,验证西断层延迟活化的主要成因是流体逐渐扩散累积到结晶基底并改变了其应力状态。此外,模拟结果表明东断层的存在使得西断层更容易活化。断层位错产生的正ΔCFS区域与诱发地震发生位置高度吻合。本文的数值模拟研究重现了水力压裂活化断层的物理过程,相关机制的正演分析若能事先开展,将可能为地震危害性预测提供科学依据。

液压支架结构的优化设计与结果

为降低压力对液压支架造成的冲击,提升液压支架的承受力,根据液压支架围岩耦合方式,在ANSYS Workbench中构建液压支架耦合模型,对受力较高的顶板通过多次迭代计算,对比其概率分布图和敏感度图像,从而得到最优结果。结果表明,优化后的最大应力值为194.37 MPa,最大应力下降28.8%;在变形正方向和负方向上,变形量分别下降11.26%和37.05%。

重复压裂气井诱导应力场模拟研究

重复压裂是低渗透油气田开发中后期增产挖潜和稳产的重要技术措施。重复压裂新裂缝的重新定向分析是具有相当难度和应用价值的核心问题,也是制约重复压裂优化设计的关键。重复压裂产生的裂缝方向取决于地应力状态,因此,垂直裂缝气井重复压裂前储层中的应力分布,尤其是水平主应力方向控制着重复压裂裂缝的起裂方位和延伸方向。系统研究了垂直裂缝井重复压裂前应力场的分布特征及其影响重复压裂气井应力大小和方向变化的主要因素。应用弹性力学和流-固耦合等理论建立了重复压裂气井的诱导应力场的数学模型,开发了相应的计算模拟程序,实现了垂直裂缝气井重复压裂前应力场的定量分析与模拟。研究表明,垂直裂缝气井中初始水力裂缝产生的诱导应力和气井生产过程中孔隙压力变化产生的诱导应力能够改变气井周围的应力场分布,并导致气井中的应力场发生重新定向。新场气田的实际运用结果也表明,重复压裂气井中的初始应力差和生产时间是决定应力重新定向的关键因素。

热-应力耦合结构灵敏度分析方法

研究稳态／瞬态热传导灵敏度分析、以及热与机械荷载同时作用的热结构应力灵敏度分析问题．考虑了温度场随设计变量的变化及其对热应力的影响，提出温度场与结构热应力耦合问题的灵敏度计算方法．特别指出了热－应力耦合灵敏度分析中温度场导数的影响；说明了在热－应力耦合结构灵敏度分析中必须考虑耦合灵敏度．在应用软件系统ＪＩＦＥＸ中实现了所提出的方法，数值算例验证了灵敏度算法的精度．

水分胁迫对紫花苜蓿根系吸水与光合特性的影响

变水条件下(利用PEG-6000模拟水分胁迫48 h,ψs=-0.2 MPa,之后复水48 h),测定紫花苜蓿(Medicagosativa L,品种阿尔冈金和陇东苜蓿)幼苗根系水力学导度与光合参数变化规律,旨在研究变水条件下紫花苜蓿光合作用的响应机制、植株水分吸收能力的变化规律及地上与地下部可能的相关关系。结果表明:干旱胁迫使得紫花苜蓿根系水力学导度(Lpr)受到显著影响。随着水分胁迫时间的延长,根系吸水能力呈现快速——缓慢下降趋势,即根系水力学导度逐渐下降,气孔导度(Gs)、蒸腾速率(Tr)、净光合速率(Pn)和叶片水势亦随之而显著降低,胞间二氧化碳浓度(Ci)先随之降低但最终上升而累积。复水后,根系水导呈现缓慢——慢速的恢复趋势,Pn、Gs、Tr、叶片水势随着根系水导速率的增加而逐渐恢复;Ci则随复水时间的延长而逐渐下降。但各参数除Ci外,均没有恢复到胁迫前水平。紫花苜蓿根系水导与光合参数在复水后的恢复程度说明,紫花苜蓿对干旱逆境的抵御与适应能力相对较弱,但陇东苜蓿对水分胁迫的忍耐能力强于阿尔冈金。