栽培太子参块根的发育解剖学研究

应用石蜡制片技术研究了栽培太子参纺锤状块根的发育过程。结果表明,栽培太子参的块根是由其不定根发育而成。太子参不定根的初生结构与次生结构的发育可分为4个阶段:原分生组织阶段、初生分生组织阶段、初生结构与次生结构阶段,类似一般草本双子叶植物根的发育。其特点是初生结构的皮层细胞大,仅3 ~4层,内皮层细胞具凯氏带;初生木质部多为三原型,少数为二原型、四原型与五原型。次生结构中次生木质部约占根面积80 %,主要为薄壁组织细胞,导管呈稀疏的放射状分布其中。由不定根发育成块根过程中,根据从根头至根尾不同距离的各组成部分的面积及细胞层数分析,从上向下其维管形成层活动强度不同,从而根的直径大小不同,使根发育成上粗下细的纺锤状肉质块根。高碘酸-Schiff反应显示,在成熟的块根中次生韧皮部的薄壁组织细胞和次生木质部射线间的木薄壁组织细胞内富含淀粉粒,在有些木薄壁组织细胞中还含有草酸钙簇晶。     

镉胁迫对吊兰及银边吊兰生长及镉富集特性的影响

选择吊兰和银边吊兰为试验材料,采用水培法研究其在不同Cd²⁺处理浓度(0、20、80、200 μmol·L^-1)下生长及生理特性的变化。结果表明: 20 μmol·L^-1镉对两种吊兰的影响较小,单叶面积、总叶面积、叶绿素(Chl)a含量、总叶绿素[Chl (a+b)]含量、类胡萝卜素含量、Chl a/Chl b值、胞间二氧化碳浓度(C_i)和蒸腾速率(T_r)与对照(CK)基本无显著差异;80 μmol·L^-1镉胁迫下两种吊兰叶片初始荧光(F_o)和非光化学淬灭系数(NPQ)升至最高水平;200 μmol·L^-1镉胁迫下,两种吊兰生物量、叶绿素含量、最大净光合速率(P_n)、气孔导度(g_s)、最大光化学量子产量(F_v/F_m)、实际光化学量子产量Y_(II)、转移系数(TF)以及各部分生物量均降至最低水平,而两种吊兰的过氧化物酶(POD)、抗坏血酸过氧化物酶(APX)及过氧化氢酶(CAT)活性和银边吊兰的丙二醛(MDA)含量均有不同程度的增加。随着镉处理浓度的增加,两种吊兰各器官Cd含量持续升高,且主要富集在根部;吊兰各器官Cd含量及富集系数(BCF)在胁迫处理下均高于银边吊兰。研究表明,两种吊兰对镉具有一定的耐性,其中吊兰对Cd的耐受能力强于银边吊兰,可考虑作为绿化植物用于修复镉污染水体或土壤。     

三七(Panax notoginseng)根残体化感自毒效应研究

为研究三七(Panax notoginseng(Burk)F.H.Chen)采收过程中残留须根的化感自毒效应,采用土培和水培2种方法,按不同比例添加三七须根粉碎物,检测根残体作用下土培三七土壤中皂苷的动态变化及水培三七根部形态结构变化。结果显示,土培条件下,随着须根粉碎物处理时间的延长,土壤中皂苷成分种类增加、总皂苷含量减少。水培条件下,随着处理时间的延长,添加须根粉碎物处理后的三七根尖细胞壁增厚,细胞中出现菌丝体;随着处理时间及处理浓度的增加,细胞开始皱缩甚至破碎,细胞中无完整细胞器结构,三七根部细胞结构差异明显。研究表明三七采收过程中残留在土壤中的须根腐解释放的化学物质可能是导致三七自毒效应的因素之一。     

桔梗根的发育解剖学研究

以桔梗(Platycodon grandiflorum A.DC)根为材料,运用石蜡切片和半薄切片法对其根的发育过程及结构进行解剖学观察,并对不同年限根的结构进行了比较。结果表明:桔梗根的结构发育过程包括原生分生组织、初生分生组织、初生生长和次生生长4个阶段。其原生分生组织由3群原始细胞组成,表现出典型分生组织的细胞学特征;初生分生组织包括根冠原、表皮原、皮层原和中柱原;初生结构由表皮、皮层和中柱组成,其中皮层薄壁细胞占主要地位,初生木质部为二原型;次生生长主要依靠维管形成层和木栓形成层的活动来完成,其次生结构从外到内由周皮和次生维管组织组成,次生维管组织占主导地位,其中以薄壁细胞为主,维管分子少量,分散在薄壁组织中。不同年限的根的结构基本相同,但它们在主根长度和直径、周皮厚度、木质部与韧皮部面积之比等方面存在差异。     

中药秦艽根内中柱裂分的发育解剖学研究

通过发育解剖学研究表明,秦艽根的初生结构正常,初生木质部四原型。次生生长早期阶段也是正常的,但天以后的次生生长过程中,由于木质部内部分薄壁细胞的分裂,且迅速 化成异常形成层细胞,并与原维管形成层相连,从而形成多个新的形成层环,将木质部柱分为几个子木质部。     

黄柳不同级序根的解剖结构及其细根的研究

采用石蜡切片法和徒手切片法对3年生黄柳不同级序的根进行解剖结构研究,并结合直径和根序对其细根进行定义,为沙生植物细根及其碳分配等相关研究提供依据。结果表明:(1)黄柳1、2级根为初生根,4、5级根为次生根,3级根为过渡型根。(2)黄柳根的初生木质部为三原型或四原型。(3)黄柳不同级序根的形态与解剖结构存在显著差异,随着根序的增加,根直径与维管柱直径逐渐增大;低级根直径主要影响因素为维管柱直径、皮层薄壁细胞直径和皮层层数;高级根直径主要影响因素为维管柱直径。(4)定义黄柳的细根为前3级根中未形成连续木栓层且直径小于0.7mm的根。该研究明确了黄柳不同级序根的解剖结构特征,并界定了黄柳细根的范围,其研究方法对于精确估计细根在生态系统中的作用具有重要的意义。     

蒙古黄芪营养器官的解剖结构研究

通过对蒙古黄芪营养器官解剖结构研究表明,根为典型的双子叶植物根的结构,初生结构由表皮、皮层和维管柱组成,初生木质部和初生韧皮部在分化过程中呈外始式,初生木质部四原型,皮层内具凯氏带;茎由表皮、皮层和维管柱组成,维管束为外韧无限维管束;叶为异面叶,由表皮、叶内和叶脉组成,栅栏组织排列紧密且整齐,细胞呈长柱形,海绵组织排列疏松且不整齐,细胞呈海绵状,有大量气隙,叶脉维管束发达,为外韧无限维管束,叶上下表皮均具有气孔.     

抗感枯萎病西瓜根际微生物比较研究

本文通过传统微生物培养方法,研究了在土培和基质培条件下,抗感枯萎病西瓜不同生育期根际和非根际微生物数量的变化.结果表明,微生物数量在根际显著高于在非根际微生物,且随西瓜生长发育的阶段不同而变化,苗期根际微生物数量最少,以后随西瓜生长发育,根际微生物数量不断增加,至生长旺盛的开花结果期,微生物数量达到最高,在西瓜生长发育后期,根际微生物数量又有所回落.西瓜抗枯萎病性与根际细菌的数量具有相关性,在生长发育各个阶段,无论是土培还是基质培,均表现为抗病材料的根际细菌数量高于感病材料的根际细菌数量.根际真菌与放线菌数量与西瓜的抗感枯萎病性没有相关性.非根际微生物数量在整个生育期变化辐度较小.非根际细菌数量在土培条件下几乎保持在同一水平,在基质培条件下迅速增加,至生长后期有所回落.非根际真菌与放线菌数量在土培和基质培条件下均于生长后期达到最高.     

玉米根系水流导度差异及其与解剖结构的关系

在人工气候室水培条件下,从单根水平研究了不同水分条件下玉米根系水流导度的基因型差异及解剖结构之间的关系.结果表明,抗旱性的杂交种户单四号具有水流导度上的杂种优势现象,不抗旱的父本803根系水流导度最低,3个品种根系水流导度大小为F₁代户单四号＞母本天四＞父本803;水分胁迫普遍降低了根系直径、导管直径和皮层厚度.同时,玉米品种根系的解剖结构和根系水流导度有关,正常水分条件下,根系导管直径与3个玉米品种的根系水流导度呈正相关,胁迫条件下则呈负相关.无论是在胁迫还是正常水分条件下,根系皮层厚度占根系直径的比例与根系水流导度都呈负相关,说明根系皮层是根系吸收水分的主要阻力部位.     

远志根的发育解剖学研究

运用石蜡切片法对远志根的发育过程及1~3年生根的结构进行解剖学研究。结果显示:远志根的原分生组织由3群原始细胞组成,具有典型分生组织的细胞学特征。初生分生组织分化为根冠原、表皮原、皮层原和中柱原;初生结构由表皮、皮层和中柱组成,初生木质部为二原型。次生生长是依靠维管形成层和木栓形成层的活动完成,次生结构从外到内由周皮和次生维管组织组成;远志根次生结构特点为:次生韧皮部在次生维管组织中占主要部分,次生韧皮部中以韧皮薄壁细胞为主且其中储存有丰富的内含物,随着根龄的增加,韧皮薄壁细胞中的内含物也随之增加。3年生的主根中次生韧皮部薄壁细胞中的内含物最丰富;不同年份远志的主根随根龄的增加,周皮、次生韧皮部和次生木质部的面积都呈增加趋势,其中韧皮部和木质部的面积比值随根龄增长呈由小到大的变化,这是远志根的显著特点;根中的周皮发达,具有较厚的木栓层,次生木质部中导管和纤维发达,导管分布频率较高,并具有较大的口径。周皮和次生木质部的结构特征与远志的抗旱特性相适应。     

Sites, pathways, and mechanism of absorption of Cu-EDDS complex in primary roots of maize (Zea Mays L.): anatomical, chemical and histochemical analysis

To study the mechanism of chelant-metal complexes to be absorbed into plant roots in the presence of different concentration chelating agents, the sites, pathways, and mechanism of absorption of Cu-EDDS complex ([S, S’]-ethylene diamine disuccinic acid) in maize (Zea mays L.) primary roots were systematically studied. The results showed that, at low concentrations of the Cu-EDDS complex (<200 μmol L^?1) in hydroponic culture, the complex was passively absorbed mainly from the apoplastic spaces where lateral roots penetrate the endodermis and the cortical region into the root xylem, the lateral root zone were the main absorption sites. At higher concentrations (<3,000 μmol L^?1), under hydroponic culture and soil culture conditions, the passage cells, which form a physiological barrier controlling ion absorption, were either injured or killed, and the complex could enter the root xylem. Injury to the physiological barrier was a key factor in the complex being absorbed by roots in substantially larger quantities. In addition, the histochemical analysis of rubeanic acid can also be used for other researches involving Cu, and the negative–pressure measuring device provides a new research tool for studying the apoplastic absorption of other metal–chelating complexes, molecules, and ions.     

Root exudation and rhizoplane bacterial abundance of barley (Hordeum vulgare L.) in relation to nitrogen fertilization and root growth

The abundance of bacteria in the rhizoplane of barley varieties was investigated at different soil nitrogen levels. Increased amendments of nitrogen resulted in higher bacterial numbers in the rhizoplane of barley seedlings of different varieties. A negative correlation was found between nitrogen level in the soil and the growth rate of the seedling roots. The effect of nitrogen on the bacterial abundances could be indirect through changed root growth and thereby changed exudation. The exudation of soluble organic carbon componds from barley seedling roots were measured in hydroponic culture. The effect of natural variation in root growth rate and of different concentrations of nitrogen in the nutrient solution was investigated. The amount of exudates consituted 2–66% of the dry weight increase in root biomass, depending on the root growth. Slower growing roots released considerably more organic carbon per unit root weight than faster growing roots. The variation in root exudation appeared to be mainly explained by differences in root growth, rather than of the nitrogen concentration in the nutrient solution. A significantly higher exudation rate was found during day time compared to night.     

Water Flow Through Cotton Roots in Relation to Xylem Anatomy

The effect of root anatomy on water flow was studied in 7-d-oldcotton (Gossypium hirsutum L.) seedlings grown in solution culture.The total water flux of the intact root system was measuredusing a pressure chamber. Then successive terminal root sectionswere removed at 2,6,10 and 12 cm behind the root tip and theflux was remeasured after each successive cut was made. Xylemdevelopment at different distances behind the root apex wasstudied with a microscope using sections cut free-hand and stainedwith toluidine blue. Water flux increased with the removal ofsuccessive terminal root sections and this coincided with thedegree of basipetal primary xylem development. The large increasein water flux at 10 to 12 cm was associated with secondary xylemdevelopment and increased xylem vessel number. A comparison of water flow and xylem anatomy between roots withtetrarch (Stoneville 506 and Deltapine 41) and pentarch (T25strain) vascular bundle arrangements showed no significant differencesin the measured values of water flux for the primary root. Waterflux, estimated using Poiseuille's equation and measured xylemdimensions, was greater for the tetrarch roots, primarily becauseof the larger diameter of individual vessel elements. The increasednumber of vessel elements in the pentarch primary root of T25did not result in any apparent decrease in axial resistanceto water flow. Key words: Gossypium hirsutum L., roots, vascular bundle, xylem water flux, xylem     

ONTOGENETIC ANALYSIS OF TREE ROOTS IN ACER RUBRUM AND BETULA PAPYRIFERA

The development of long (6-20 m) tree roots was reconstructed from serial transverse sections taken 10-20 cm apart. Measurements of primary xylem diameter showed that the tips of long roots of red maple (Acer rubrum L.) and paper birch (Betula papyrifera Marsh.) are initially small, but they increase in diameter with increasing distance from the stem. A repeating pattern of the width of the first annual ring marks length increments of long roots. The pattern of ring width is paralleled by a pattern of primary xylem diameter. Our interpretation is that primary xylem diameter increases during spring and early summer, stays constant during late summer and decreases in autumn. After injuries to large root tips, new large lateral tips are formed that replace the parent tip. Thus, a single long root is actually formed by a succession of these replacement roots. In a series of sections there may be sudden changes in primary xylem diameter as the successive sections pass from parent root to replacement root at points of injury. These changes in birch are associated with changes in a number of protoxylem poles.     

Cu2O纳米颗粒对小麦根系形态及遗传毒性的影响

为了阐明Cu₂O纳米颗粒(NPs)暴露对植物根系的毒性效应,本研究以小麦品种‘周麦18’为材料,采用水培试验方法,研究了10、50、100和200 mg·L^-1浓度的Cu₂O-NPs对小麦幼苗生长、根系活性、形态结构及细胞遗传学毒性的影响。结果表明: 不同浓度的Cu₂O-NPs降低了小麦幼苗的根芽长度、鲜重、根活性和根冠比,增加了初生根的数量;随着Cu₂O-NPs浓度的升高,幼苗根伸长区缩短、根系变硬变脆、根径增加、根冠变大;100 mg·L^-1浓度的Cu₂O-NPs处理下,小麦根尖有丝分裂指数显著降低,根尖细胞形状不规则化、质壁分离、细胞出现空泡化、细胞核核膜模糊、核内染色体异常。在水培条件下,Cu₂O-NPs对小麦幼苗具有一定的遗传学毒性效应,从而影响小麦幼苗的生长发育和根系形态结构。     

Linking root morphology, longevity and function to root branch order: a case study in three shrubs

Root branching order supports a powerful approach to understanding complex root systems; however, how the pattern of root morphological characteristics, tissue carbon (C) and nitrogen (N) concentrations, and root lifespan are related to anatomical features of variable root orders for mature shrubs (～19 years old) in sandy habitats is still unclear. In this study, these relationships were investigated for three typical shrubs in Horqin Sand Land, Northeast China. Root diameter, individual root length, tissue carbon concentration, C:N ratio, root lifespan, root cross-sectional area (CSA), stele CSA, proportion of stele in root CSA, mean xylem vessel CSA and the number of xylem vessels all increased with root order for the three shrubs, while specific root length and nitrogen concentration decreased with root order. The combined root biomass of the first two orders accounted for more than 63% of the first–fourth order root biomass for all the three shrubs. Proportion of stele to root CSA and number of xylem vessels of third-order root segments were significantly higher than that of the first two orders, and third-order roots showed secondary development with a continuous cork layer. All first-order and most second-order roots exhibited primary development, had an intact cortex, a lower proportion of stele to root CSA, and a smaller number of vessels. Our research suggests that the first two order roots of shrubs in sandy habitats are responsible mainly for absorption, and that they play a major role in root turnover and C and N flux in the soil organic matter pool due to their high proportion of biomass and N concentration, as well as their short lifespan.     

不同培育方式对橡胶树实生苗生理指标、养分及长势的影响

橡胶树(Heveabrasiliensis)种子催芽生长一般使用沙床培育,沙子是不可再生资源,为了选择一种适合橡胶树种子培育方式来替代对沙子的依赖,该研究通过水培、悬空培育和传统的沙培比较橡胶树实生苗第1蓬叶稳定时,苗木的生长势、生理指标及养分含量。结果表明,水培实生苗地上部株高、茎粗、叶面积的长势最佳,壮苗指数和生物量的含量最高,但其根太长,根相对较细。水培的叶、茎、根的可溶性糖、丙二醛、游离脯氨酸、超氧化物歧化酶的含量均较低;水培和悬空培育的叶片和茎的叶绿素、类胡萝卜素及根系活力的含量没有显著性差异,均高于沙培。水培的叶、茎、根中的氮和磷含量最低,沙培的最高;而水培实生苗根和茎中钾的含量较高,叶片中含量与悬空培育、沙培均没有显著性差异;悬空培育在叶、茎、根中钾的含量最低。水培促进了苗木的生长,降低干旱胁迫,提高养分利用率,但后续还需调控根系,建设良好根团。悬空培育的苗木长势较弱,还需进一步完善方法。     

Uptake of amino acids by plants from the soil: A comparative study with castor bean seedlings grown under natural and axenic soil conditions

Castor bean seedlings grown in different media (soil, quartz sand, or liquid culture) under natural or axenic conditions take up¹⁴C labelled proline when offered to the rooting medium at concentrations similar to those occuring in the soil. Most of the absorbed proline was transferred through the root into the xylem without metabolic conversion, though some conversion to glutamine and alamine occurred.It is concluded that roots successfully compete with microorganisms for free amino acids in the soil for the following reasons: (a) The initial rate of appearance of radioactivity in the xylem sap was the same in plants grown in natural or in axenic soil, and (b) the specific activity of proline in the xylem sap was approximately the same in plants grown in natural conditions and in axenic soil (even somewhat higher under natural condition).The role of soil microorganisms became evident however in long-term experiments (e.g. 5h), because the soil solution was much more rapidly depleted of labelled amino acids in natural soil than in axenic soil. Therefore after 20 hours roots grown in sterilized soil or quartz sand always contained more¹⁴C label than those grown in natural soil.It is suggested that viable roots use free amino acids from the soil and that the main flux of carbon to the rhizosphere might be in the form of organic acids.     

The influence of slope on <Emphasis Type="Italic">Spartium junceum</Emphasis> root system: morphological,anatomical and biomechanical adaptation

Root systems have a pivotal role in plant anchorage and their mechanical interactions with the soil may contribute to soil reinforcement and stabilization of slide-prone slopes. In order to understand the responses of root system to mechanical stress induced by slope, samples of Spartium junceum L., growing in slope and in plane natural conditions, were compared in their morphology, biomechanical properties and anatomical features. Soils sampled in slope and plane revealed similar characteristics, with the exception of organic matter content and penetrometer resistance, both higher in slope. Slope significantly influenced root morphology and in particular the distribution of lateral roots along the soil depth. Indeed, first-order lateral roots of plants growing on slope condition showed an asymmetric distribution between up- and down-slope. Contrarily, this asymmetric distribution was not observed in plants growing in plane. The tensile strength was higher in lateral roots growing up-slope and in plane conditions than in those growing down-slope. Anatomical investigations revealed that, while roots grown up-slope had higher area covered by xylem fibers, the ratio of xylem and phloem fibers to root diameter did not differ among the three conditions, as also, no differences were found for xylem fiber cell wall thickness. Roots growing up-slope were the main contributors to anchorage properties, which included higher strength and higher number of fibers in the xylematic tissues. Results suggested that a combination of root-specific morphological, anatomical and biomechanical traits, determines anchorage functions in slope conditions.     

两个不同耐旱性棉花品种根系生理特性对干旱的响应

为探明不同抗旱性棉花品种的根系生理特性对干旱的响应及其与生物量的关系,以不耐旱性品种‘新陆早17号'(L17)和耐旱性品种‘新陆早22号'(L22)为试材,在土柱栽培条件下设常规灌溉(CK)、轻度干旱(W₁)和中度干旱(W₂)处理,研究干旱胁迫对不同耐旱性棉花品种根系活力、保护酶活性及解剖结构(导管直径、数量)和生物量的影响。结果表明:干旱胁迫下两棉花品种根系可溶性蛋白(SP)含量、根系活力(RV)、木栓层数、根茎导管数量、导管直径显著降低,根系丙二醛(MDA)含量及保护性酶活性显著增加,进而导致地上部干物质量显著降低。与L17相比,L22的SP含量、0～40 cm和80～120 cm土层RV、木栓层数、根茎导管数量、导管直径以及地上部干物质量均显著增加,尤其W₂条件下L22的RV降幅比L17低26.2%,过氧化氢酶(CAT)、过氧化物酶(POD)和超氧化物歧化酶(SOD)活性和皮层厚度分别比L17高43.6%、6.9%、25.4%、19.9%,且差异均达到显著水平。干物质量与RV、SOD、POD、木栓层数、导管直径和个数之间均呈显著正相关。因此,耐旱性强的棉花品种在干旱条件下通过保持较高的根系活性、木栓层数、导管直径和数量,进而促进地上部生物量积累,是其具有较高耐旱性的生理机制。