植物根系吸水机理的研究进展

近年来,植物根系吸水机理在细胞、组织和整体水平上的研究进展非常迅速,对阐明植物抗旱机制及其高效利用有限水资源途径的探讨具有重要意义.本文主要对植物根的复合结构和根系在土壤中的分布、根系中水流性质等方面的最新研究状况进行了概述,特别详细地论述了水通道蛋白的表达及功能与根系中水分运动的关系、以及根系输水的调节和根系吸水过程中的信号传导方面的研究动态,并且评价了根的复合运输模型和根系吸水的数学模型等,最后就其可能生理意义及其应用前景作了评述.     

植物根系吸水模型研究进展

植物根系吸水模型是当前生态水文和陆面过程建模领域最为活跃的研究方向,是研究流域水文、生态、环境以及水资源可持续利用等科学问题中最为关键的部分,研究植物根系吸水的物理和生理机制及其影响因素,是建立植物根系吸水模型的基础.本文通过对植物根系吸水模型研究的回顾,讨论了水分和盐分胁迫在根系吸水中的作用、根系吸水的多维模型、根系吸水在陆面过程中的作用等问题,指出植物根系吸水模型发展所面临的问题并展望了未来的发展方向.     

植物根际微生物群落构建的研究进展

植物根际是指植物根系与土壤的交界面,是根系自身生命活动和代谢对土壤影响最直接、最强烈的区域,其物理、化学和生物性质不同于土体土壤。在这个区域里,与植物发生相互作用的大量微生物,被称为根际微生物。根际微生物在植物的生长发育和植物病虫害的生物防治等方面都具有十分重要的意义。本文总结了根际微生物群落构建的研究现状,介绍了根际微生物的经典和最新的研究方法,包括根箱法、同位素技术以及高通量测序、菌群定量分析、高通量分离培养等方法在根际微生物研究中的应用,讨论了植物根系分泌物(碳水化物、氨基酸、黄酮类、酚类、激素及其信号物质)和土壤物理化学性质对根际微生物群落的影响,概述了根际微生物-植物的互作机制,以及根际微生物群落对植物的促生作用、提高植物抗逆性和抑制作用,并对根际微生物群落研究中存在的问题和未来发展方向进行了展望。     

植物根构型的定量分析

植物根系具有锚定植株、吸收和运输土壤中的水分及养分、合成和贮藏营养物质等重要功能。根构型是根系在土壤中的空间造型和分布。对植物根构型进行定量分析, 有助于人们了解根系结构和根系功能在生态系统中的重要作用。本文对植物根构型的概念及其定量分析研究进展进行了概述, 并介绍了植物根构型的主要研究方法和定量分析技术。     

植物根构型的定量分析

植物根系具有锚定植株、吸收和运输土壤中的水分及养分、合成和贮藏营养物质等重要功能。根构型是根系在土壤中的空间造型和分布。对植物根构型进行定量分析,有助于人们了解根系结构和根系功能在生态系统中的重要作用。本文对植物根构型的概念及其定量分析研究进展进行了概述,并介绍了植物根构型的主要研究方法和定量分析技术。     

植物根系分泌物主要生态功能研究进展

根系分泌物在植物根系-土壤-微生物互作过程及其生态反馈机制中发挥重要作用。在植物根际复杂网络互作过程中, 根系分泌物被认为是“根际对话”的媒介, 其在调控植物适应微生境、缓解根际养分竞争及构建根际微生物群落结构方面意义重大。该文结合国内外该领域主要研究成果, 综述了根系分泌物对植物生长、土壤微生物特性及土壤养分循环的影响, 并展望了未来根系分泌物的研究方向。     

根压与根系的主动吸水

植物根系吸收水分有两种类型:被动吸水和主动吸水,被动吸水的动力是蒸腾拉力,主动吸水的动力是根压。我认为根压不是植物根系吸水的动力,而应当是植物根系吸水的结果。理由有三点: 第一,根压的定义没有“根压是根系主动吸水的动力”的含义。“根系的生理活功使液流上升的压力称为根压”。“根压是由于根系代谢活动的结果,使木质部导管分子内产生     

湿地植物根系泌氧及其在自然基质中的扩散效应研究进展

湿地植物根系径向泌氧(ROL)是构造根际氧化-还原异质微生态系统的核心要素,其扩散层为好氧、厌氧微生物提供了良好生境并促进其代谢活动,使湿地植物根际成为有机物降解、物质循环及生命活动最为强烈的场所,已有成果证明湿地植物根系ROL的强弱与污染物的去除效果密切相关。因此,开展湿地植物根系ROL及其在自然基质中的扩散效应研究,对于了解湿地植物根系ROL机理及其根际氧环境特征,进而发挥湿地植物的污染去除功能具有十分重要的意义。基于此,首先归纳了湿地植物根系ROL特征及其受影响机制的研究现状,而后从种属差异、时空分布及对微生物的影响等方面对根系ROL在自然基质中的扩散效应国内外研究成果进行了总结,最终根据研究现状与不足对今后的研究方向进行了简要展望。创新之处在于:1)提出影响根系氧供给及氧输送释放通道的环境、生物等因素,阐述了其对根系ROL的影响机制;2)着重阐述了目前研究较少提及的根系ROL扩散效应测定方法。     

Research Advances in the Main Ecological Functions of Root Exudates

根系分泌物在植物根系-土壤-微生物互作过程及其生态反馈机制中发挥重要作用。在植物根际复杂网络互作过程中, 根系分泌物被认为是“根际对话”的媒介, 其在调控植物适应微生境、缓解根际养分竞争及构建根际微生物群落结构方面意义重大。该文结合国内外该领域主要研究成果, 综述了根系分泌物对植物生长、土壤微生物特性及土壤养分循环的影响, 并展望了未来根系分泌物的研究方向。     

植物水分生理教学中的两个问题

根压与根系吸水根压是植物根系的生理活动使液流从根部上升的压力。一些教科书中将根压视为根系吸水的动力之一,认为根压把根部的水分压到地上部,土壤中的水分便不断补充到根部,这就形成了根系吸水过程。这是不正确的。根系利用代谢能,主动地将土壤中的溶质吸收到内皮层内部,又主动(或被动)地将吸收的溶质转移到导管中,使导管溶液的浓度高于外部溶液的浓度,通     

Changes in Root Hydraulic Conductivity During Wheat Evolution

A better understanding of the mechanisms of water uptake by plant roots should be vital for improving drought resistance and water use efficiency (WUE). In the present study, we have demonstrated correlations between root system hydraulic conductivity and root characteristics during evolution using six wheat evolution genotypes (solution culture) with different ploidy chromosome sets (Triticum boeoticum Bioss., T. monococcum L.: 2n=2x=14;T. dicoccides Koern., T. dicoccon (Schrank) Schuebl.:2n=4x=28;T. vulgare Vill., T. aestivum L. cv. Xiaoyan No. 6:2n=6x=42). The experimental results showed that significant correlations were found between root system hydraulic conductivity and root characteristics of the materials with the increase in ploidy chromosomes (2x→6x) during wheat evolution. Hydraulic conductivity of the wheat root system at the whole-plant level was increased with chromosome ploidy during evolution, which was positively correlated with hydraulic conductivity of single roots, whole plant biomass,root average diameter, and root growth (length, area), whereas the root/shoot ratio had an inverse correlation with the hydraulic conductivity of root system with increasing chromosome ploidy during wheat evolution. Therefore, it is concluded that that the water uptake ability of wheat roots was strengthened from wild to modern cultivated species during evolution, which will provide scientific evidence for genetic breeding to improve the WUE of wheat by genetic engineering.     

Changes in Root Hydraulic Conductivity During Wheat Evolution

A better understanding of the mechanisms of water uptake by plant roots should be vital for improving drought resistance and water use efficiency (WUE). In the present study, we have demonstrated correlations between root system hydraulic conductivity and root characteristics during evolution using six wheat evolution genotypes (solution culture) with different ploidy chromosome sets (Triticum boeoticum Bioss., T. monococcum L.: 2n = 2x = 14; T. dicoccides Koern., T. dicoccon (Schrank) Schuebl.: 2n = 4x = 28;T. vulgare Vill., T. aestivum L. cv. Xiaoyan No. 6: 2n = 6x = 42). The experimental results showed that significant correlations were found between root system hydraulic conductivity and root characteristics of the materials with the increase in ploidy chromosomes (2x→6x) during wheat evolution. Hydraulic conductivity of the wheat root system at the whole-plant level was increased with chromosome ploidy during evolution, which was positively correlated with hydraulic conductivity of single roots, whole plant biomass,root average diameter, and root growth (length, area), whereas the root/shoot ratio had an inverse correlation with the hydraulic conductivity of root system with increasing chromosome ploidy during wheat evolution. Therefore, it is concluded that that the water uptake ability of wheat roots was strengthened from wild to modern cultivated species during evolution, which will provide scientific evidence for genetic breeding to improve the WUE of wheat by genetic engineering.     

Inoculation with arbuscular mycorrhizal fungi enhances growth of Litchi chinensis Sonn. trees after propagation by air-layering

This study investigated the patterns of root growth and water uptake of maize (Zea mays L.) and cowpea (Vigna unguiculata (L.) Walp) grown in a mixture under greenhouse conditions. The plants were grown in root boxes for 5 weeks under 2 watering regimes; fully irrigated and water stress conditions, followed by a 5-day drying cycle imposed during the 6th week of growth. Water uptake patterns were analysed during the drying cycle. The two-dimensional distribution of the roots of both plants in the boxes was determined immediately at the end of the drying cycle. Under well-irrigated conditions, the roots of the component plants grew profusely into all sections of the root box and intermingled considerably. Water stress resulted in the decline of root growth of maize and cowpea but the root:shoot ratios of maize and cowpea were not affected, suggesting that there was no significant effect of water stress on root:shoot partitioning. However, water stress affected the biomass distribution between fine and coarse roots in cowpea. About 64% by weight of cowpea roots under water stress were coarse whereas as against 48% under well-irrigated conditions. Furthermore, water stress generally restricted the lateral extent of the roots of both maize and cowpea with a tendency of clumping together of the root systems and a reduced degree of intermingling. Thus, the extent of mixing of the root systems was apparently controlled by the availability of soil water. Water uptake from the well-irrigated soil in the root boxes was initially restricted to the sections directly below the base of each plant. Although roots of both plants were present in almost all sections of the root box, all the sections did not contribute simultaneously to water uptake by each plant. Water uptake was delayed from the middle intermingled zones. In effect, uptake patterns did not relate generally to the root distribution. The tendency was for the component plants to initially `avoid' water uptake from zones of intense intermingling or competition.     

Potassium uptake by plants,as characterized by root density,species and K/Rb ratio

Summary A small fraction of the plant K requirement is attained by root interception. The bulk of K has to be transported to the growing roots by mass-flow and diffusion in which diffusion mechanism plays the major role. Studies were undertaken to evaluate soil and plant parameters that might have influence on K supply mechanisms in soil and on plant uptake of K. Increasing wheat plant density led to competition for K absorption and resulted in lower K uptake by plant. In high plant density treatment, about 60% of the K requirement was met by diffusion process whereas in low plant density treatment mass-flow contributed most of the K demand. Solution diffusion and mass-flow were the major mechanisms of K supply to wheat roots. The mechanism of K supply to wheat root was compared with corn and onion. The major mechanism of K supply to corn and onion roots was exchange and solution diffusion. The mechanism of K supply to different crop species is attributable to differences in the K requirements, water flux rates and to the differences in root parameters.     

Water uptake by plant roots: an integration of views

A COMPOSITE TRANSPORT MODEL is presented which explains the variability in the ability of roots to take up water and responses of water uptake to different factors. The model is based on detailed measurements of 'root hydraulics' both at the level of excised roots (root hydraulic conductivity, Lp_r) and root cells (membrane level; cell Lp) using pressure probes and other techniques. The composite transport model integrates apoplastic and cellular components of radial water flow across the root cylinder. It explains why the hydraulic conductivity of roots changes in response to the nature (osmotic vs. hydraulic) and intensity of water flow. The model provides an explanation of the adaptation of plants to conditions of drought and other stresses by allowing for a `coarse regulation of water uptake' according to the demands from the shoot which is favorable to the plant. Coarse regulation is physical in nature, but strongly depends on root anatomy, e.g. on the existence of apoplastic barriers in the exo- and endodermis. Composite transport is based on the composite structure of roots. A `fine regulation' results from the activity of water channels (aquaporins) in root cell membranes which is assumed to be under metabolic and other control.     

植物根系和叶片生长对水分亏缺的原初反应

细胞扩张生长是植物受水分亏缺影响最敏感的生理过程之一。主要在对细胞水分导性、细胞壁特性和延伸组织中溶质传输结果分析的基础上 ,从细胞、组织和器官水平上对细胞扩展生长进行了探讨。根系和叶片细胞主要通过以下 2个过程来补偿水分胁迫的作用 :调节扩展生长需要的细胞临界膨压 ;溶质在延伸组织中的运移。此外 ,还探讨了植物根系和叶片生长对水分亏缺的生理适应机制     

非均匀水势下作物根系吸水模型分析

根据土壤-根系统中水分守恒和水势对水分运输作用的原理, 建立了土壤中非均匀水势作物根系吸水模型。在该模型中, 分别对一次函数和指数函数两种不同的非均匀土壤水势的表达形式建立模型, 并对非均匀水势和均匀水势下模型的解析解之间的关系进行了探讨; 利用该模型讨论根系的吸收阻力和木质部传导阻力的比率对根吸水的影响; 运用阻力比率的合理生理范围确定根生长的优化长度。结果表明: 在特定情况下, 非均匀水势下的根系吸水模型可以用于均匀水势, 对Poiseuille公式进行修正后得到的根的优化长度接近实际值。     

A model for water uptake by plant roots

We present a model for water uptake by plant roots from unsaturated soil. The model includes the simultaneous flow of water inside the root network and in the soil. It is constructed by considering first the water uptake by a single root, and then using the parameterized results thereby obtained to build a model for water uptake by the developing root network. We focus our model on annual plants, in particular the model will be applicable to commercial monocultures like maize, wheat, etc. The model is solved numerically, and the results are compared with approximate analytic solutions. The model predicts that as a result of water uptake by plant roots, dry and wet zones will develop in the soil. The wet zone is located near the surface of the soil and the depth of it is determined by a balance between rainfall and the rate of water uptake. The dry zone develops directly beneath the wet zone because the influence of the rainfall at the soil surface does not reach this region, due to the nonlinear nature of the water flow in the partially saturated soil. We develop approximate analytic expressions for the depth of the wet zone and discuss briefly its ecological significance for the plant. Using this model we also address the question of where water uptake sites are concentrated in the root system. The model indicates that the regions near the base of the root system (i.e. close to the ground surface) and near the root tips will take up more water than the middle region of the root system, again due to the highly nonlinear nature of water flow in the soil.