The Floral Nectary of Tropaeolum majus L.--The Nature of the Secretory Cells and the Manner of Nectar Secretion

The floral nectary of Tropaeolun majus L. was studied with theaid of a microscope with transmitting and incident light, atransmission electron microscope and a scanning electron microscope.The Gomori method was used for the localization of acid phosphatase.As a result of this investigation the previously accepted viewthat nectar in this plant is secreted only from the hair tipsof the inner epidermis of the calyx spur was found to be inaccurate.The present studies showed that the parenchyma cells locatedbetween the inner epidermis and the region of the vascular bundlesof the lowest third of the spur, are the main nectar-secretingelements of the nectary. These secretory cells release the nectarsolution into intercellular spaces leading to modified stomata,through which it is exuded into the spur cavity. The modifiedstomata occur in the lowest portion of the spur only. At thestage of secretion small droplets of liquid of high viscositywere observed on the epidermal hairs. These droplets presumablycontain polysaccharides and a certain amount of sugar.     

星星草营养器官适应盐胁迫的结构特征

采用0．6％Na2CO3胁迫处理星星草[Puccinellia tenuiflora（Turcz．）Scribn．et Merr．]幼苗,光镜和电镜观察其根和叶的显微和超微结构。结果表明,星星草根的表皮向外突出形成密集的根毛;外皮层由1～2层细胞组成,排列较紧密;中皮层薄壁细胞排列疏松,形成发达的通气组织;内皮层呈典型的五面加厚;中柱鞘排列紧密,其壁加厚;初生木质部与初生韧皮部相间排列,初生木质部为5～7原型,中央为后生木质部导管,无髓存在。叶的表皮有表皮毛和丰富的蜡质层;叶上表皮泡状细胞数目较少,且深陷;气孔下陷,其下有较大的气室;叶脉有大、中、小3种维管束,大、中型维管束为C3型,小型维管束为C4型。星星草可能是介于C3和C4植物之间的类型,具有耐盐碱及耐干旱特征。     

F肌动蛋白作为胞间连丝组分的结构与生理学证据

以蒜 (AlliumsativumL .)瓣鞘外表皮为材料 ,利用荧光特异探针与共焦镜检术 ,结合透射电镜与免疫金标记对表皮细胞间胞间联络的性质、结构进行了系统观察。结果表明 ,加厚壁上的通道是由狭长的管状胞质和初生纹孔场上成束的胞间连丝衔接组成 ,前者实为原生质体的一部分。单个胞间连丝的孔径为 6 0～ 70nm ,属正常胞间连丝范围 ,它们乃相邻细胞间共质联系的所在。荧光探针TRITC_Phalloidin (TRITC_Ph)标记的结果显示 ,整个通道上呈现红色荧光的纤索在接近初生纹孔场处明显变窄 ,与超微结构观察中所见的结构特点相吻合 ,共焦镜下观察到的初生壁上的荧光亮斑乃初生纹孔场中成束胞间连丝被标记的反映 ,从而有效地证实了F肌动蛋白在常态胞间连丝上的存在。免疫金标记实验显示在管状胞质中和胞间连丝上有金颗粒分布 ,这一结果为证实荧光标记物具肌动蛋白性质提供了有说服力的补充。     

Formation of intercellular gas space in the diaphragm during the development of aerenchyma in the leaf petiole of Sagittaria trifolia

The development of aerenchyma in the petiole of Sagittaria trifolia L. was studied by means of light-microscopy, scanning electron microscope, transmission electron microscope and immunofluorescence, focusing on the formation of intercellular spaces in diaphragms and its relationship with the organization of cortical microtubule arrays. A complex and organized honeycomb-like schizogenous aerenchyma formed by cylinders and vascular diaphragms was observed in the petiole of S. trifolia at different developmental stages. Cell division was the primary factor contributing to the increased volume of air spaces at early stages, while cell enlargement became the primary factor at later stages. The cortical microtubules localize at the sites where intercellular spaces and the secondary cell walls will be formed or deposited during the formation of intercellular spaces by the separation of diaphragm cells. Cortical microtubules were observed at the boundary of diaphragm cells and the fringes of intercellular spaces at later developmental stages where cell expansion occurs rapidly. These observations support the hypothesis that reorganization of cortical microtubule arrays might be related to the formation of air spaces in diaphragms and are involved in the deposition of secondary cell walls.     

A study of the source of virus in the Pholem exudate appearing on leaves of Amscinckia infected with the beet curly top virus

Abstract Leaves of Amsinckia douglasiana discharging phloem exudate after infection with the beet curly top virus (BCTV) were studied with the electron microscope. Infected tissue differed from the noninfected in having much hyperplastic phloem characterized by abnormally high proportion of sieve elements, scarcity of companion cells, degenerating parenchyma cells, and some unusually large intercellular spaces. Many spaces contained amorphous debris. Particles resembling BCTV were discernible within the debris. Such particles were encountered also in the debris trapped between stomatal guard cells. Since the phloem exudate excreted from leaves of BCTV-infected plants contains virus particles, and since the virus is found extremely rarely in sieve elements, we suggest (1) that most of BCTV particles apparently released into intercellular spaces are derived from degenerating parenchyma cells in which the virus had multiplied; (2) that the exudate is derived from sieve elements of the hyper-plastic phloem in which the normal functional control by companion cells is lacking; (3) that the exudate leaks from the nontransporting sieve elements through cell walls into intercellular spaces and carries the virus to the outside. Initially, stomata may serve as exits for the infectious exudate, but subsequently ruptures in the epidermis are involved.     

The vascular plant‐pathogenic bacterium Ralstonia solanacearum produces biofilms required for its virulence on the surfaces of tomato cells adjacent to intercellular spaces

The mechanism of colonization of intercellular spaces by the soil‐borne and vascular plant‐pathogenic bacterium Ralstonia solanacearum strain OE1‐1 after invasion into host plants remains unclear. To analyse the behaviour of OE1‐1 cells in intercellular spaces, tomato leaves with the lower epidermis layers excised after infiltration with OE1‐1 were observed under a scanning electron microscope. OE1‐1 cells formed microcolonies on the surfaces of tomato cells adjacent to intercellular spaces, and then aggregated surrounded by an extracellular matrix, forming mature biofilm structures. Furthermore, OE1‐1 cells produced mushroom‐type biofilms when incubated in fluids of apoplasts including intercellular spaces, but not xylem fluids from tomato plants. This is the first report of biofilm formation by R. solanacearum on host plant cells after invasion into intercellular spaces and mushroom‐type biofilms produced by R. solanacearum in vitro. Sugar application led to enhanced biofilm formation by OE1‐1. Mutation of lecM encoding a lectin, RS‐IIL, which reportedly exhibits affinity for these sugars, led to a significant decrease in biofilm formation. Colonization in intercellular spaces was significantly decreased in the lecM mutant, leading to a loss of virulence on tomato plants. Complementation of the lecM mutant with native lecM resulted in the recovery of mushroom‐type biofilms and virulence on tomato plants. Together, our findings indicate that OE1‐1 produces mature biofilms on the surfaces of tomato cells after invasion into intercellular spaces. RS‐IIL may contribute to biofilm formation by OE1‐1, which is required for OE1‐1 virulence.     

Biochemical Characteristics of Rice Endophytic DiazotrophicBacteria and Their Infection to Tobacco and Maiz

Some biochemical properties of rice endophytic diazotrophic bacteria N1 ( Bacillus pumilus), N2 ( Enterobacter cloacae) and N3 ( Enterococcus gallinarum) were characterized in this study. The plasmids harboring the reporter gene lacZ fused to the promoters of nifH and nifHDK, and the reporter gene gfp as well, were first transformed into rice endophytic diazotrophic bacteria respectively through triparental mating. After the conjugated bacteria were inoculated into tobacco Yunyan 85 and maize Jitian 6, the staining of β-galactosidase was carried out on the tobacco and maize roots and the observation was made under the confocal laser scanning microscope, transmission electron microscope and scanning electron microscope. The results showed that the rice endophytic diazotrophic bacteria were not only present in epidermal cells, cortex cells and intercellular spaces of tobacco and maize roots, but also found in vascular tissue cells of maize stem also, indicating that the bacteria had migrated from the roots into the stem. Data showed that the the fresh weight of maize plants inoculated with rice endophytic diazotrophic bacteria N3 was 18.52% more than that of the control.     

Ultrastructural studies on migrating epidermal cells during the wound healing stage of regeneration in the adult newt, Notophthalmus viridescens

The ultrastructure of the epidermal cells which migrate over the wound surface of the amputated limb of the adult newt, Notophthalmus viridescens, was observed with transmission (TEM) and scanning (SEM) electron microscopy. In order to aid in the visualization of polyanionic surface materials on the wound epithelium and wound surface with TEM, the basic dye, ruthenium red, was introduced into the fixatives and buffer. Control limbs were processed without ruthenium red. Shortly after amputation, basal cells at the wound margin possessed elongated, flattened profiles with long pseudopodial projections (lamellipodia and filopodia) that appeared to make contact with the fibrin exudate covering the stump tissues. Epidermal cells proximal to the site of amputation were also in a state of mobilization. Large intercellular spaces and a reduction in the number of desmosomes were observed in the migrating cells. Epidermal cell nuclei became characteristically euchromatic with well-developed nucleoli. Microfilaments were seen within the cytoplasm, extending toward the plasma membrane of cellular processes. Phagocytosed material was also present in the migrating cells. By approximately 9 hours post-amputation, wound closure was complete, and the wound epithelium consisted of three to four cell layers of a non-cornified epidermis. Generally, the amount of extracellular material present on the surface and in the enlarged intercellular spaces of migrating epidermal cells remained the same throughout the period of wound closure. A layer of polyanionic material was observed consistently over the fibrin meshwork covering the wound surface with TEM.     

灵武长枣正常果及裂果中Ca2+的细胞化学定位研究

采用焦锑酸钾沉淀法,对灵武长枣正常果发育过程中的Ca2+及不同开裂度果实中的Ca2+进行细胞化学定位,在透射电镜下观察并比较Ca2+的分布特征和积累规律.结果表明:(1)正常长枣青果期的外果皮细胞及胞间隙中检测到大量的钙沉淀颗粒,而果肉细胞以及叶绿体中很少有钙沉淀颗粒.红果期很多外果皮细胞中钙沉淀颗粒特异性地沿细胞壁呈一圈分布,且越靠近内方的细胞中钙沉淀颗粒越少、越小.果肉细胞中仍无钙沉淀颗粒分布.(2)具轻微开裂的长枣很多外果皮细胞中无钙沉淀颗粒,只有少数细胞中有且集中分布于大液泡中;细胞质沿细胞壁分布,也无钙沉淀颗粒;在果肉细胞中几乎看不到钙沉淀颗粒分布.(3)完全开裂的长枣中钙沉淀颗粒只分布在少数体积较小的外果皮细胞中,而果肉细胞的细胞壁边缘或细胞壁以及胞间隙中分布有大量的钙沉淀颗粒.     

A correlated histochemical and ultrastructural study of the epidermis and hypodermis of onion roots

Summary Cell walls of mature epidermal and hypodermal cells are autofluorescent when viewed under ultraviolet or blue light. This autofluorescence develops in a centripetal direction, beginning in the outer tangential wall of the epidermis and ending in the inner tangential wall of the hypodermis. The intercellular regions between the epidermis and hypodermis and between the hypodermis and the cortex are dense and also become autofluorescent. Although the walls of the hypodermis provide a barrier to the movement of a high molecular weight fluorescent dye, the walls of the epidermis are permeable. Histochemical studies indicate that lipids and polyphenolics are components of the epidermal and hypodermal cell walls. Both layers are resistant to the wall-degrading enzyme Driselase and to concentrated sulphuric acid, whereas the cortex is digested with both treatments. Observations with the transmission electron microscope show that a complex suberin lamella encases each hypodermal cell but is absent from the epidermis. However, the outer tangential wall and radial walls of the epidermal cells are complex in that layers of different densities are present. Some of these layers, as well as the intercellular regions and the radial walls of the hypodermal cells, bind ferric ions when tissue is fixed in ferric chloride-glutaraldehyde indicating the presence of poly-phenolics in these regions. An extracellular layer covering the outer tangential wall of the epidermis stained positively with a number of histochemical tests for polyphenolics.     

国产润楠属植物的叶表皮特征及其系统学意义

对45种国产润楠属(Machilus Nees)植物的叶表皮进行光学显微镜和扫描电镜观察,其中31种为首次报道.结果表明:润楠属植物叶表皮细胞形状为多边形或不规则形,气孔复合体均为平列型且仅分布在下表皮;上下表皮细胞的垂周壁式样有5种类型:平直、圆滑、浅波、波状、平直-弓形;下表皮毛被有(稀疏、密集或非常密集)或无;上表皮平周壁纹饰类型有:点状、平滑、条纹(或波浪条纹);下表皮内面平周壁纹饰类型有:不规则、平滑、粗糙网状、微毛状、颗粒状、鳞片状.这些特征在本属种间存在较显著的差异,可作为区分种类的辅助特征和种间亲缘关系,因而对润楠属植物的分类学研究和亲缘关系的确定有较大意义.     

热胁迫下不结球白菜和甘蓝叶片组织结构的变化

利用显微及扫描电镜方法,研究不结球白菜及甘蓝的耐热品种和感热品种种在高温（３８－３９℃）胁迫下,叶片表皮和组织结构的差异。结果如下：耐热品种叶片下表皮比感热品种气孔频度高,气孔体积小且开张度小。耐热品种部分气孔呈关闭状态,而感热品种气孔基本上呈开放状态。显微结构观察到耐热品种叶肉组织细胞排列紧密,叶脉的维管束发达,特别是木质部的导管数量多且孔径大。而感热品种相比于耐热品种叶肉细胞排列疏松,维管束相     

Aerenchyma tissue development and gas-pathway structure in root of Avicennia marina (Forsk.) Vierh.

The aerenchyma differentiation in cable roots, pneumatophores, anchor roots, and feeding roots of the mangrove plant, Avicennia marina (Verbenaceae) was analyzed using a light microscope and scanning electron microscope. In all types, cortex cells were arranged in longitudinal columns extending from the endodermis to the epidermis. No cells in the cortex had intercellular spaces at the root tip (0–150 m), and aerenchyma started developing at 200 m from the root apex. The aerenchyma formation was due to cell separation (schizogeny) rather than cell lysis. The cell separation occurred between the longitudinal cell columns, forming long intercellular spaces along the root axis. During aerenchyma formation, the cortex cells enlarged longitudinally by 1.8–3.9 times and widened horizontally by 2.2–2.9 times. As a result, the aerenchyma had a pronounced tubular structure that was radially long, elliptical or oval in cross section and that ran parallel to the root axis. The tube had tapering ends, as did vessel elements, although there were no perforated plates. The interconnection between neighboring tubes was made by abundant small pores or canals that were schizogenous intercellular spaces between the wall cells. All aerenchyma tubes in the root were interconnected by these small pores serving as a gas pathway.     

Fine structure of the epidermis of the mudskipper,Periophthalmus modestus (Gobiidae)

The ultra-structure of the epidermis of the mudskipper,Periophthalmus modestus, was examined by both light and transmission electron microscopies. The epidermis is exceptionally not well endowed with mucous or granular cells. Filament-containing cells occur in three distinct layers of the surface, middle and basal epidermis. The surface layer is further subdivided into two layers, an outermost and less superficial one. Two different cell types were identified in the epidermis. Type I cells are fiat cells in a single stratum. Type II cells are enormous cells, characterized by having a large vacuole in the cytoplasm. The outermost layer is composed of a free surface of Type I cells and numerous microridges covered with a fuzzy, fibrillar substance. The “fuzz” forms a cuticule-like structure, but keratinization as found in terrestrial animals does not occur. The superficial layer contains Type I cells and intraepithelial blood capillaries. When Type I cells become senescent, numerous intercellular spaces are formed in the plasma membranes of adjacent cells, with the senescent cells finally falling off. Just beneath these cells, however, young cells of Type I are always found. The blood capillaries are usually reinforced with young Type I cells. A large volume of oxygen may be absorbed through the skin using the blood capillary network. The middle layer contains several strata of Type II cells. The special corky structure of these cells seems to play an important role in thermal insulation and protection against ultraviolet light in relation to life out of water. However, by comparison with terrestrial animals, the histological design of the epidermis of this goby appears incomplete, so as to reduce desiccation on land, owing to the epidermis lacking a keratinized stratum. The differentiation of the epidermis seems to be an adaptation for a terrestrial habit in this species.     

Differential ultrastructural changes in tomato hormonal mutants exposed to cadmium

Cadmium (Cd) is a toxic heavy metal, which can cause severe damage to plant development. The aim of this work was to characterize ultrastructural changes induced by Cd in miniature tomato cultivar Micro-Tom (MT) mutants and their wild-type counterpart. Leaves of diageotropica (dgt) and Never ripe (Nr) tomato hormonal mutants and wild-type MT were analysed by light, scanning and transmission electron microscopy in order to characterize the structural changes caused by the exposure to 1 mM CdCl₂. The effect of Cd on leaf ultrastructure was observed most noticeably in the chloroplasts, which exhibited changes in organelle shape and internal organization, of the thylakoid membranes and stroma. Cd caused an increase in the intercellular spaces in Nr leaves, but a decrease in the intercellular spaces in dgt leaves, as well as a decrease in the size of mesophyll cells in the mutants. Roots of the tomato hormonal mutants, when analysed by light microscopy, exhibited alterations in root diameter and disintegration of the epidermis and the external layers of the cortex. A comparative analysis has allowed the identification of specific Cd-induced ultrastructural changes in wild-type tomato, the pattern of which was not always exhibited by the mutants.     

红豆草根瘤侵入线的超微结构研究

用透射电镜对红豆草根瘤侵入线的超微结构进行了观察研究.结果表明,(1)红豆草根瘤侵入线由胞间隙和胞间层细胞壁内陷形成,它们的体积较小,多为管状,基质丰富,含菌很少,常有分叉和1个以上的基质区,而且不同基质区的电子密度、细菌数量和侵入线壁厚度都不相同.(2)红豆草根瘤的侵入线十分丰富,它们不仅大量存在于根瘤分生细胞和幼龄侵染细胞中,也经常出现在发育成熟的侵染细胞内.(3)红豆草根瘤中有一种近似圆形的特殊结构,表面由一层膜包围,其内电子密度较低且无固定结构,且只位于侵染细胞的细胞质中,常在侵入线附近,从不出现在侵染细胞的液泡内和非侵染细胞里面.     

Surface and subsurface structures of neuromasts in tadpoles of the crab-eating frog, Rana cancrivora

Neuromast structure in Rana cancrivora larvae was observed by scanning and transmission electron microscopy. Neuromast units, each being composed of two or three neuromasts, are arranged in several well-defined lines in the head, body, and tail regions. The structure of neuromasts in these three regions is basically identical. The neuromast is composed of sensory, sustentacular, and mantle cells. The top of each neuromast has a hillocklike appearance, and is surrounded by four to six epidermal cells with tight intercellular junctions. Long kinocilia and many stereocilia occur in the apex of the neuromasts and are surrounded by numerous microvilli. Numerous granules are present on the apical portions of the mantle and the sustentacular cells. Four or five trapeziform mantle cells are connected closely with each other to form the shell of the neuromast. Large intercellular spaces occur between the mantle cells and the cells of the inner epidermal layers, and between the cells of the inner epidermal layer. Thus, at the apical parts of the neuromast intercellular junctions are tight and the intercellular spaces are more dilated in more basal areas. Morphologically the neuromasts of R. cancrivora larvae resemble those of generalized pond anurans, based on the grouping of Lannoo (Journal of Morphology 191:115-129, 1987a), although larvae of this species inhabit brackish water.     

蕤核的花粉形态及叶片微观结构

运用光学显微镜和扫描电镜对蕤核的花粉形态及叶片微观结构进行了观察。结果表明:蕤核花粉体积小,近球形,辐射对称,具三沟,外壁具条纹状纹饰。上下表皮均有角质层,但形态不同。下表皮有气孔分布,气孔略下陷,气孔密度每平方毫米200～300个,气孔存在三种状态。叶片为异面叶,栅栏组织细胞由2～3层柱状细胞构成,排列紧密,海绵组织由管状细胞构成,细胞间隙大。蕤核虽属于中生植物,但叶片微观结构趋近于旱生植物的特征。     

小麦类根瘤中胞间细菌的运动及其对细胞壁的影响

用电子显微镜和光学显微镜观察了小麦类根瘤,以探讨小麦类根瘤中胞间细菌的运动及其对细胞壁的影响.结果表明:(1)小麦类根瘤由薄壁细胞、分生细胞和侵染细胞组成,它们中有许多胞间隙,其中一些还含有大量细菌;它们的胞间层常常彼此分离,形成间隙,间隙中有时也有细菌存在;(2)小麦类根瘤中没有侵入线,细菌运动主要在胞间进行;具有细菌的胞间隙和胞间层大小不等、形状各异,其细胞壁还常常出现不同程度的变化,变化的大小一般与它们中的细菌有关,且随细菌数量的增加而增加.     

Ultrastructural localization of silver deposits in the receptacle cells of carnation flowers

Carnations were treated with a silver thiosulphate complex to prevent wilting of the flowers. The ultrastructural localization of silver and sulphur in the receptacle tissue was investigated by electron microscopy. Electron-dense deposits were present in the receptacle tissue. Coarse-grained deposts (diam. 60–100 nm) were predominantly observed at the inner side of the cell wall, whereas fine-grained deposits (diam. 20–60 nm) were predominantly present inside the cell-wall region and in the intercellular spaces. These particles were analyzed for chemical elements by X-ray analytical electron microscopy (Philips EM 400 plus Edax energy dispersive analyzer, type 711). In both types of deposits, the presence of silver and sulphur was verified. Point analysis revealed that in both precipitates the S/Ag ratio was of the same order.Abbreviations CTEM conventional transmission electron microscope - STEM scanning transmission electron microscope The AEM unit is a joint unit of the Erasmus University of Rotterdam, the University of Leyden, and the Health Organization TNO. The analytical microscope was purchased with a grant from the Dutch Organization for Pure Scientific Research (ZWO) through BION