人参根系发育形态学的研究

人参(Panax qinseng C. A. Meyer)属于直根系植物,有次生构造。一年生苗只具有主根和侧根。二年以上的人参常在根状茎上长出不定根,即人参根系包括主根和不定根及其各级分枝。主根初生木质部为三原型,侧根和不定根及其分枝多为二原型,偶见三原型。根系随参龄的增加而增大。每年末级分枝自基部于休眠前萎缩、脱落,并在萎缩部分的上一级支根内部产生越冬根原基,越冬根原基是翌年形成全部吸收根的基础。一年生人参由中柱鞘产生一圈初生树脂道,由形成层产生一圈(或二圈)次生树脂道,以后次生树脂道的圈数随参龄的增加而每年增加一圈,自第五年开始渐缓。根内淀粉粒含量随发育时期的变化而相应变化,其积累高峰出现在果后期。研究人参根系发育形态学不仅对全面正确认识人参根系具有理论意义,而且对改进人参栽培管理和评价人参质量具有指导意义。     

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。     

水氮处理下不同品种水稻根系生长分布特征

为明确不同栽培条件下水稻(Oryza sativa)根系生长分布特征, 通过不同水氮处理和不同品种的水稻桶栽试验, 采用内置根架法, 于拔节期和抽穗期取样, 获取根系总干重(TRW)、不定根数(ARN)以及各类根(不定根、细分枝根和粗分枝根)的形态指标(长度、表面积和体积), 并分析植株根系生长状况和根系分布特征。结果显示: (1)各试验条件下抽穗期各项根系指标较拔节期均呈增长趋势。同一时期, 各项根系指标在3个施氮水平间均差异显著, 且随施氮量的增加而增加。不同水分处理下, 两个时期的ARN在湿润灌溉(W2)与保持水层(W1)之间差异均不显著, 而其他指标上W2处理均显著最高; 干旱处理 (W3)下, 仅拔节期的TRW和粗分枝形态指标与W1处理接近, 而在其他指标上均显著最低。不同品种间, ‘扬稻6号’ (V3)的各项根系指标均最高, 而‘日本晴’ (V1)和‘武香粳14’ (V2)间差异不显著。(2)各试验条件下, 抽穗期较拔节期根系下扎生长比例增加, 多分布于表层(0-5 cm)土中; 减少氮素和水分供应可提高根系在5 cm以下土层中的分布比例, 且分枝根反应最为明显; 品种V1和V2的深扎根性较V3明显。结果表明, 合理施氮与控水可优化水稻不同类型根的生长与分布特征, 但需考虑不同品种之间的差异。     

细叶马先蒿根系发育形态学研究

细叶马先蒿为玄参科多年生草本植物。年生产周期明显缩短。根系营养生长至花期为粗壮主根与纤细侧根并存,果期侧根几乎全部枯萎脱落,所存留根系皆呈乳白色。由胚根形成的初生主根根毛密集,初生木质部二原型。侧生分生组织只有形成层而无木栓形成层。根表皮细胞经解离后略呈不规则方形片状,横切面为平周长梭形,进行垂周分裂增加梭形根表皮细胞长度,以适应根的增粗生长。根表皮脱落时,外皮层以同样生长方式代替脱落的表皮。在年     

干旱荒漠区狭叶锦鸡儿灌丛扩展对策

通过对内蒙古干旱荒漠区狭叶锦鸡儿集群的灌丛结构、分株特征、繁殖倾向和分枝特征的调查,探讨荒漠区狭叶锦鸡儿的繁殖特点和灌丛扩展对策。研究表明：在荒漠区,狭叶锦鸡儿的营养繁殖占主导地位,主要是由根萌蘖产生无性系分株,其克隆生长构型为密集型。根系萌蘖、枝条的不定根繁殖、地上枝条不断分枝和新老个体形成复合灌丛是荒漠区狭叶锦鸡儿冠幅增大的主要原因。狭叶锦鸡儿通过克隆繁殖、灌丛扩大化和发达的根系适应荒漠区的干旱贫瘠环境,使其成为荒漠区的优势种。     

空心莲子草根中异常结构及不定芽的发育解剖学研究

运用光镜和扫描电镜的方法 ,观察了空心莲子草根的结构及不定芽的结构 ,结果表明 :根的初生木质部为二原型、三原型和四原型 ;初生结构和早期次生结构正常 ,异常的次生生长是由于次生韧皮部外侧发生的额外形成层所致 ,后一轮额外形成层起源于前一轮向外产生的薄壁细胞 ,结合组织为发达的薄壁细胞 ,二至四轮三生维管束排成整齐的同心环类型 ,不定芽主要起源于异常根的额外形成层 ,芽外有二至三轮鳞片 ,其内着生许多毛状物。     

怀地黄块根的形态发生和结构发育

观察了怀地黄(Rehmannia glutinosa cv．Hueichingensis Hsiao．)块根的形态发生和生长发育过程中的形态结构变化。采用怀地黄的传统栽培方法,即用上一年的块根作母根进行繁殖,分别从母根和不定芽的茎基部发生不定根。怀地黄不定根的初生结构和维管形成层的发生与一般双子叶植物相同,但其次生生长却有两种方式,即正常次生生长和异常次生生长。一类不定根的形成层产生的次生结构与一般双子叶植物相同,即次生木质部中主要是导管,而薄壁细胞较少。这类不定根其次生生长为正常次生生长(normal secondary growth),是担负吸收和固着作用的正常根。另一种类型的不定根,其形成层产生的次生木质部含有大量的薄壁细胞,少量的导管分散在薄壁细胞之间。这种次生生长为异常次生生长(anomalous secondary growth),从而使不定根膨大,形成块根。因此,怀地黄的药用部分在起源和结构上都属于根的性质,其药用部分应称为块根。     

旋扭山绿豆（Desmodium intortum）营养器官的形态解剖特点与高固氮、耐阴和水土保持的关系

旋扭山绿豆（Ｄｅｓｍｏｄｉｕｍｉｎｔｏｒｔｕｍ）不仅是营养价值高的牧草,而且是耐阴、高固氮和适于水土保持的植物。本植物由主根、各级侧根和不定根组成庞大的根系．各种根都可长出根瘤。其根瘤形成时间较早．数量较多．８５％以上为有效根瘤．类菌体力棒形．茎半匍匐,分枝多,复盖面积大,节及节间都能产生不定根。其叶较薄．气孔较少．叶绿体较大．其内淀粉粒少．基粒片层较丰富,因而能耐阴、在２０％遮阴下生长最好。     

濒危药用植物桃儿七根的显微结构及其菌根真菌分布研究

本文研究了桃儿七Sinopodophyllum hexandrum根的显微结构及其真菌分布。结果表明,桃儿七的根为根状茎,节状,不定根形成的须根系发达。根的结构主要由表皮、皮层、维管柱三部分构成,其中,皮层所占比例最大,超过80%。根的木质部有四原型和五原型两种类型,五原型较为常见;四原型的根和五原型的根在皮层细胞形态上存在一定差异。在桃儿七的不定根和其上的侧根观察到真菌菌丝分布,其数量和种类与根的直径有关,在不定根较细(先端)的部位真菌以暗色有隔内生真菌(DSE真菌)为主,侵染率为77.9%;而较粗根中真菌菌丝为无隔菌丝为主,分布很少且仅存在于皮层细胞的一至二层,不侵染皮层深部和维管柱。不定根侧根中真菌以丛枝菌根真菌为主,丛枝菌根常常占据大部分的皮层细胞,侵染率高达90%以上。桃儿七根中没有发现根毛存在,因此,侧根中共生的丛枝菌根真菌可能是桃儿七养分和水分吸收的主要途径。     

欧美杂种山杨微扦插不定根发生过程的解剖学研究

采用石蜡切片技术,以欧美杂种山杨插穗基部茎段为实验材料,连续解剖观察插穗不定根发生发育过程,分析根原基发生部位与扦插生根的关系。结果显示:欧美杂种山杨插穗不定根的发生过程分为4个时期,为根原基诱导期,不定根起始期、表达期和伸长生长期。根原基诱导期维管形成层产生具有分生组织特点的薄壁细胞;不定根起始期,维管形成层及附近的薄壁细胞脱分化,形成不定根原基发端细胞;不定根表达期,根原基发端细胞不断分裂成具有方向性的根原基,根原基穿过韧皮射线和皮层,向皮孔方向发展;不定根伸长生长期,根原基从皮孔伸出,其内部的维管系统开始发育,形成不定根。研究认为,欧美杂种山杨为皮部诱导生根类型,不定根原基起源于维管形成层区,起源部位单一,扦插难生根。     

ANATOMY OF SEEDLING ROOTS OF PSEUDOTSUGA MENZIESII

The seedling root system of Pseudotsuga menziesii (Mirb.) Franco consists of the primary root, active long laterals, long laterals that become mycorrhizal, and short roots that may or may not become mycorrhizal. Numerous adventitious roots arise from the pericycle in young roots and from the vascular cambium and pericycle in older roots following pruning. All actively growing apices have a single plate of initials, a complex zonation of mother cells, and a similar pattern of primary tissue differentiation. Short roots and mycorrhizal short roots have 2 plates of initials, one producing the stele and the other the root cap and cortex, and differentiation occurs close to the apex. Primary and adventitious roots are usually triarch, while long laterals are usually diarch as are all short roots. The latter lack secondary xylem, but mycorrhizal short roots may produce a small amount of secondary phloem.     

二月兰根系发育形态学研究

二月兰Ｏｒｙｃｈｏｐｈｒａｇｍｕｓ ｖｉｏｌａｃｅｕｓ Ｏ．Ｅ．Ｓｃｈｕｌｚ为二年生草本植物,直根系。初生结构为二原型,次生结构发达,主侧根结构相同。形成层活动随季节有明显变化,木质部可见年轮。冬季吸收根不死,无越冬根原基产生,吸收根连续不断更替,无明显季节性变化。根内淀粉含量随发育时期的变化而相应变化,其积螺高峰有两个,分别出现在第一年越冬前及第二年返青后开花前,不同播期对根系积累营养及第二年植     

小麦种子根的发育解剖

小麦胚胎发育过程中通常形成5条幼根(少数可形成6条),这些根统称为种子根,中间最先发生的为初生根.初生根的原基在胚胎发育的早期就在胚轴的一侧发生,原基细胞由不规则到规则排列。侧生种子根的原基在胚胎发育后期才出现,通常成对发生,并且是由胚轴上的节(盾片节和胚芽鞘节)维管束外方的细胞形成。侧生种子根的发育明显较初生根的快,分化能力也较强,后生木质部导管母细胞出现早,数目较多.因此,小麦胚胎发育过程中从胚轴上形成的这些侧生的种子根,形态上,仍应看作是一些不定根,其结构特征与后来形成须根系的不定根的比较近似。     

RHABDOXYLON AMERICANUM SP. N., A STRUCTURALLY SIMPLE FERN-LIKE PLANT FROM THE UPPER PENNSYLVANIAN OF ILLINOIS

A new species of the genus Rhabdoxylon Holden (1960), an anatomically simple plant of presumed fern or fern-like affinities, is described from a coal ball petrifaction found in the Upper Pennsylvanian of southern Illinois. The new species, R. americanum, is based upon five specimens consisting of stems bearing spirally arranged leaves and numerous randomly distributed adventitious roots. The haplostelic stems branch by equal dichotomies and bear foliar traces which arise as unequal dichotomies of the stele. Leaf traces possess a circular outline in cross section and one adaxial protoxylem strand. The characteristics of exclusively primary tissues, diarch adventitious roots, centrarch haplosteles with simple scalariform pitting, and the nature and arrangement of the leaf traces, suggest that Rhabdoxylon represents a fern or fern-like plant rather than a representative of the Rhyniophytina or Trimerophytina. At present it is not possible to determine whether the simple structure of Rhabdoxylon has come about through phyletic reduction or represents a primitively simple condition.     

ROOT GLOCHIDS AND ROOT SPURS OF OPUNTIA ARENARIA (CACTACEAE)

Root glochids of Opuntia arenaria Engelm. are produced by adventitious buds (areoles) that arise endogenously on fleshy roots. If they remain active, root areoles become dwarf shoots that initiate only glochids and trichomes unless the roots are uncovered or the shoots bearing the roots are removed. Then they will expand, producing aerial shoot joints. Root spurs are formed in great numbers on the profusely branched system of small roots. They consist of clusters of rootlets about one mm long that are initiated in sympodial sequence, each new rootlet arising endogenously near the base of the preceding one. On older spurs this results in the formation of a short axial peg. Rootlet primordia lack a root cap from the beginning and appear to mature quickly, losing all their meristematic characteristics and becoming completely covered with root hairs, even over the tip. They may represent a mechanism for the rapid production of root hairs during the infrequent periods when moisture is available. In any case, they seem to be transitory structures because cork soon forms beneath the older ones on a spur.     

Increase of root induction in Pinus nigra explants using agrobacteria

Summary Wounding of explanted Pinus nigra primary explants followed by infection with Agrobacterium rhizogenes wild strains 8196, 15834, or with the pRiA4abc transconjugant strain of A. tumefaciens (C58 chromosomal background) resulted in adventitious root induction. Roots were formed in 60–97% of explants (1–3 roots/explant) but without a hairy root phenotype. The presence of T-DNA of pRi8196 or pRiA4abc in regenerated roots was confirmed by the opine (mannopinic acid) content. Transformation response was influenced by the bacterial strain, age of explant and period of co-cultivation. Both the aggregate state (liquid) of medium and the season of the year (spring) had a positive effect on the root induction and their development. Histological analysis of the transformed roots showed that complete elements of primary and secondary root structures were present but roots were always triarch or tetrarch in the central cylinder as opposed to the primary roots of the untransformed seedling wich are diarch.     

ORIGIN AND EARLY DEVELOPMENT OF NONARTICULATED LATICIFERS IN EMBRYOS OF EUPHORBIA MARGINATA

In E. marginata 12 nonarticulated laticifer initials arise in the cotyledonary node of the young embryo during the early heart stage. The initials arise progressively in the developing embryo, the first laticifers differentiating simultaneously with or shortly before the elements of the pro-cambium. The laticifers occupy a position lateral to the six procambial strands which are formed in the embryo. Upon subsequent growth each laticifer becomes vacuolated and nuclear division unaccompanied by cytokinesis results in the formation of a coenocytic protoplast. The enlarging laticifer produces several branches, one growing into the cotyledon, another growing down along the hypocotyl penetrating toward the root meristem, and one or several growing along intercellular spaces of adjacent cells. No fusion of these branches with one another or adjoining parenchyma cells was observed.