植物生理学研究中的压力探针技术

压力探针技术是一种用来测定微系统中压力大小和变化的新技术。其最初被设计用于直接测定巨型藻类的细胞膨压。随着操作装置的进一步微型化和精密化,后来被应用于测定普通高等植物细胞膨压及其它水分关系参数。该技术的发展建立在一系列相应的流体物理学理论基础上。通过这些物理学公式的计算,该技术能测定跨细胞膜或器官的水分运输速度以及它们的水力学导度;测定溶液中水分和溶质的相对运输速度以及它们之间的相互影响;还可以测定细胞壁的刚性等。目前压力探针技术已成为植物生理学和生态学领域研究中的多用途技术。它可以在细胞水平上原位测定水分及溶质跨膜运输及分布情况,这对于阐明水通道功能具有极其重要的意义。此外,木质部压力探针技术是目前唯一可以直接测定导管或管胞中负压的工具。该技术还可以用于单细胞汁液的样品采集,结合微电极技术测定导管或其它细胞中的pH值、离子浓度以及细胞膜电位。本文重点介绍该技术使用的基本原理和相应的理论基础,并详细地描述了操作过程中的技术和技巧。     

植物生理学研究中的压力探针技术

压力探针技术是一种用来测定微系统中压力大小和变化的新技术。其最初被设计用于直接测定巨型藻类的细胞膨压。随着操作装置的进一步微型化和精密化, 后来被应用于测定普通高等植物细胞膨压及其它水分关系参数。该技术的发展建立在一系列相应的流体物理学理论基础上。通过这些物理学公式的计算, 该技术能测定跨细胞膜或器官的水分运输速度以及它们的水力学导度; 测定溶液中水分和溶质的相对运输速度以及它们之间的相互影响; 还可以测定细胞壁的刚性等。目前压力探针技术已成为植物生理学和生态学领域研究中的多用途技术。它可以在细胞水平上原位测定水分及溶质跨膜运输及分布情况, 这对于阐明水通道功能具有极其重要的意义。此外, 木质部压力探针技术是目前唯一可以直接测定导管或管胞中负压的工具。该技术还可以用于单细胞汁液的样品采集, 结合微电极技术测定导管或其它细胞中的pH值、离子浓度以及细胞膜电位。本文重点介绍该技术使用的基本原理和相应的理论基础, 并详细地描述了操作过程中的技术和技巧。     

植物木质部压力探针测定技术与方法

木质部压力探针技术是目前直接测定植物木质部导管负压的唯一手段。在结构上,木质部压力探针测定系统由精密操作装置、压力探针系统和信号采集—传输一显示系统三大部分组成。其测定原理是将毛细管探针刺入木质部导管,通过传导介质将木质部导管负压传至压力传感器,压力传感器感应压力并将压力信号输出。本文从玻璃毛细管探针的制作、去气泡水的制备以及压力探针的校准、安装、测定等方面详细介绍了木质部压力探针的使用方法和注意事项。     

植物水分生理研究中的压力-容积测定技术几个关键问题

传统的压力-容积(pressure-volume,PV)技术是通过测定植物组织细胞从吸水饱和状态直至膨压消失的失水全过程中水势与相对含水率,并建立两者之间的关系,从而获得其他方法难以获取的植物水分生理参数(如:质壁分离渗透势、饱和渗透势、质壁分离相对含水量、细胞弹性模量)。这些参数与植物耐旱性密切关联,反映植物组织在干旱期维持功能的能力,因而使该技术在揭示树木因水力衰竭而死亡的生理机制中发挥重要作用。然而,该技术在试验材料预处理、测定、计算方法等关键步骤上尚存在问题。为此,本文针对这些潜在问题,结合中国应用研究现状,对PV技术进行综述,并提出相应的建议。     

植物体内水分长距离运输的生理生态学机制

植物体内长距离水分运输是植物生理生态学研究中的一个重要问题,长期为植物生理学家和生理生态学家所关注。木质部探针技术的问世,掀起了近年来植物生理学界最为激烈的一场争论。提出了已经有100多年,风行40年的内聚力-张力(Cohesion-Tension, C-T)学说受到质疑。随后维护派和质疑派围绕木质部探针技术、压力室技术(C-T理论的主要支撑实验技术)的可靠性展开辩论。进一步从物理学原理和各种实验上就C-T理论的3个支柱(木质部导管或管胞中巨大的张力、沿树高的压力梯度、连续水柱)进行争论。这场争论似暂告一段落,C-T理论没有被推翻,但仍留有问题期待以后的研究。     

水分胁迫下高粱叶片的渗透调节与延伸生长的关系

高粱抗旱品种3197B比不抗旱品种三尺三在水分胁迫条件下ψ_S下降低。在相同ψ_S时,3197B相对含水量高于三尺三。水分胁迫期间,3197B能始终维持比三尺三较高的ψ_P。在中度和严重水分胁迫时,3197B几种渗透物质积累均高于三尺三,其中可溶性糖和K~ 对渗透调节贡献最大。水分胁迫下,3197B正展开叶渗透调节能力较强,ψ_P维持较高,临界膨压低,叶片扩张性能小、故生长速率随ψ_W下降较慢。     

镧定位法在生物研究中的应用

利用稀土镧具有的一些特殊性质,结合电子显微技术,通过其在细胞中的定位,可对生物系统中的一些过程进行更广泛的研究。１稀土定位的原理及技术稀土离子在碱性条件下可与溶质的某些盐类生成电子束不能穿透的致密沉淀物,利用此特性,采用特殊生物制片技术即可将离子沉积...     

稳定同位素技术在植物水分利用研究中的应用

近20a稳定同位素技术在植物生态学研究中的应用得到了长足发展,使得对植物与水分关系也有了更深一步的了解。介绍稳定同位素性碳、氢、氧同位素在研究植物水分关系中的应用及进展,以期能为国内植物水分利用研究提供参考。由于植物根系从土壤中吸收水分时并不发生同位素分馏,对木质部水分同位素分析有助于对植物利用水分来源,生态系统中植物对水分的竞争和利用策略的研究,更好地了解生态系统结构与功能。稳定碳同位素作为植物水分利用效率的一个间接指标,在不同水分梯度环境中,及植物不同代谢产物与水分关系中有着广泛的应用。同位素在土壤-植被-大气连续体水分中的应用,有助于了解生态系统的水分平衡。随着稳定同位素方法的使用,植物与水分关系的研究将取得更大的进展。     

碳稳定同位素技术在植物水分胁迫研究中的应用

植物体的碳稳定同位素组成主要由植物本身的生物学特性决定 ,但环境胁迫对其影响也十分明显。综述了碳稳定同位素技术在研究植物水分利用效率、生物量高低及判断历史气候依据等研究领域的进展 ,阐明了植物体的 δ1 3C值对干旱、盐分及其它环境因素的变化所引起的水分胁迫的响应 ,并对碳稳定同位素对水分胁迫的响应机理进行了归纳和推断     

水分胁迫下ABA由蚕豆根向地上部的运输及其在叶片组织中的分布

蚕豆根装载的３Ｈ－ＡＢＡ可经５．６ｃｍ／ｍｉｎ以上的速率向冠部运输。短时间内（５ｍｉｎ）根运来的ＡＢＡ主要分布在有大量气孔密布的下表皮,但长时间内（３ｈ）则主要分布在对内组织中。抑制蒸腾可降低ＡＢＡ向叶片中的运输积累。光镜放射自显影术显示,根运来的ＡＢＡ可有效地在表皮细胞及保卫细胞的质外体积累。３Ｈ－ＡＢＡ由根向地上部快速运输及其在作用部位的有效积累,说明水分胁迫下蚕豆根部可以通过ＡＢＡ信号的传递控制气孔的行为。     

Leaf Diffusive Conductance and Tap Root Cell Turgor Pressure of Sugarbeet

Abstract. The interrelationships of leaf diffusive conductance, tap root cell turgor pressure and the diameter of the tap root of sugarbeet were studied. The study was conducted on well-watered plants growing in pots under artificial light in the glasshouse. In a typical experiment, on illumination (400 μmol m⁻² s⁻¹) leaf conductance increased from 0.6 to 7.4 mm s⁻¹. Cell turgor pressure in the tap root decreased from 0.8 MPa to 0.45 MPa and the root diameter (9.0 cm) contracted by 145μm. Removal of light resulted in the reversal of each of the above parameters to their previous values. Quantitively similar results were obtained when sugar beet plants were uprooted and the response of each of the parameters was measured. The sequence of events however was different. On stimulation by light, changes in leaf diffusive conductance preceded the turgor and root diameter changes (which were simultaneous) by some 15–20min. In contrast, on uprooting the simultaneous changes in root turgor pressure and diameter preceded the changes in leaf conductance. The lag times between changes in diffusive conductance and turgor pressure in the root were between 20 and 30 min.
Tap root turgor pressure and diameter correlated strongly and permitted the calculation of an apparent whole root volumetric elastic modules (55–63 MPa). The small changes in tissue volume relative to the transpiration rate suggest that the tap root is not a significant source of transpirational water during the day.     

The plant cell pressure probe

The pressure probe is a micro manometer for the simultaneous direct recording and manipulation of plant cell hydrostatic pressure. It is used to map in space and time the turgor pressures of individual cells within tissues and organs of intact plants. This is used to study the hydraulic architecture of tissues, tissue movement and the responses of tissues to water stress. The approach can be augmented by simultaneous measurement of individual cell osmotic pressure. This permits the hydraulic driving forces across selectively permeable membranes and walls to be assessed fully. By manipulating manually the pressure, cell wall elasticity and its properties can also be mapped. Under some conditions this can be extended to plastic behaviour.     

Seasonal changes in tissue elasticity in chaparral shrubs

An important physiological feature of chaparral shrubs is the development of low water potentials during periods of drought characteristic of southern Californian summers. Changes in tissue elasticity may be an important characteristic allowing these low water potentials to be reached and maintained without the development of detrimental water deficits. To examine this possibility, seasonal changes in tissue elasticity were measured in 3 species of chaparral shrubs, Arctostaphylos glandulosa Eastw., Quercus dumosa Nutt. and Ceanothus greggii Gray., by the pressure-volume method. Tissue elasticity was characterized using graphs of the modulus of elasticity plotted as a function of turgor pressure, and maximum values of the elastic modulus. The moduli of elasticity of the shrubs increased following leaf emergence in the spring, were highest during periods of low soil water potential, and tended to decrease following the summer-fall drought period. Increases in tissue elasticity facilitate water uptake from drying soils, but result in greater turgor loss during tissue dehydration.     

Xylem and cell turgor pressure probe measurements in intact roots of glycophytes: transpiration induces a change in the radial and cellular reflection coefficients

Xylem probe measurements in the roots of intact plants of wheat and barley revealed that the xylem pressure decreased rapidly when the roots were subjected to osmotic stress (NaCl or sucrose). The magnitude of the xylem pressure response and, in turn, that of the radial reflection coefficients (σ_r) depended on the transpiration rate. Under very low transpiration conditions (darkness and high relative humidity), σ_r assumed values of the order of about 0·2–0·4. The σ_r values of excised roots were also found to be rather low, in agreement with data obtained using the root pressure probe of Steudle. For transpiring plants (light intensities at least 10 μmol m^?2 s^?1; relative humidity 20–40%) the response was nearly 1:1, corresponding to radial reflection coefficients of σ_r= 1. Further increase of the light intensity to about 400 μmol m^?2 s^?1 resulted in a slight but significant decrease of the σ_r values to about 0·8. Similar measurements on maize roots confirmed our previous results (Zhu et al. 1995, Plant, Cell and Environment 18, 906–912) that, in intact transpiring plants at low light intensities of about 10 μmol m^?2 s^?1 and at relative humidities of 20–40% as well as in excised roots, the xylem pressure response was much less than expected from the external osmotic pressure (σ_r values 0·3–0·5). In contrast to wheat and barley, very high light intensities (about 700 μmol m^?2 s^?1) were needed to shift the radial reflection coefficients of maize roots to values of about 0·9. Osmotically induced xylem pressure changes were apparently linked to changes in turgor pressure in the root cortical parenchyma cells, as shown by simultaneous measurements of xylem and cell turgor pressure. In analogy to the σ_r values of the respective glycophytes, the σ_c values of the root cortical cells of wheat and barley were close to unity, whereas σ_c for maize was significantly smaller (about 0·7) under laboratory conditions. When the light intensity was increased up to about 700 μmol m^?2 s^?1 the cellular reflection coefficient of maize roots increased to about 0·95. In contrast to the σ_r values, the σ_c values of the three species investigated remained almost unchanged when the leaves were exposed to darkness and humidified air or when the roots were cut. The transpiration-dependent (species-specific) pattern of the cellular and radial reflection coefficients of the root compartment of the three glycophytes apparently resulted from (flow-dependent) concentration-polarization and sweep-away effects in the roots of intact plants. The data could be explained straightforwardly terms of theoretical considerations outlined previously by Dainty (1985, Acta Horticulturae 171, 21–31). The far-reaching consequences of this finding for root pressure probe measurements on excised roots, for the occurrence of pressure gradients under transpiring conditions, and for the non-linear flow-force relationships in roots found by other investigators are discussed.     

盐胁迫下大麦根系木质部压力的自调节现象

用植物木质部压力探针测定的结果表明,水培大麦幼苗根的木质部压力在环境条件恒定不变时始终保持波动,并且在受到轻度的盐胁迫和当盐胁迫解除时表现出高度的自调节现象.这种波动和自调节现象将对植物水势的测定和根的径向反射系数的测定产生很大的影响,并可能与植物的抗盐性有关.小麦根在同样条件下未表现出上述现象.