Developmental changes in the inner epidermis of the bean seed coat

Summary The inner epidermis of the bean seed coat shows remarkable structural changes during seed development. At the globular stage of development, a moderately electron-dense substance begins to accumulate in the outer tangential and radial walls of the cells. The staining and fluorescence characteristics, together with the localization of peroxidase in the wall, suggest that this electron-dense material is a phenolic substance. At the same stage of embryo development, structural specialization can be detected in the cytoplasm of the epidermal cells with an increase in the abundance of organelles, especially the endoplasmic reticulum, mitochondria, and dictyosomes. These structural features are similar to those in the underlying branched parenchyma cells. As the seed rapidly expands during the maturation stage of embryo development, the epidermal cells and the inner layers of the branched parenchyma cells begin to degenerate. Small ruptures can be detected in the epidermis, exposing the branched parenchyma cells. These structural changes are discussed in relation to their possible functions during embryo development.     

Microtuboli in Cellule Parenchimatiche ed Epidermiche di Coleottile di Avena

Abstract

Microtubules in parenchyma and epidermis cells of avena coleoptile. — The fine structure of differentiating parenchyma and epidermis cells of the oat coleoptile, fixed in glutaraldehyde-osmium tetroxide, or glutaraldehyde-potassium permanganate, was investigated. Tubular structures have been observed aligned in the peripheral cytoplasm, between the cell wall and the plasma membrane, embedded in the cell wall and inside the tonoplast in the vacuoles.

The nature and function of these structures are yet unknown. Microtubular structures, localized beneath and above the plasma membrane, have been associated to the wall development; the function of the microtubules observed in vacuoles results, anyhow, of far problematic interpretation.     

Spatial and temporal aspects of cell separation in the foliar abscission zones ofImpatiens sultani Hook

Summary The abscission of leaves fromImpatiens sultani Hook. occurs as the direct result of the weakening of a narrow band of cells running transversely across the base of the petiole. This loss of strength of the abscission zone is due to the breakdown of the central cell wall in two or three layers of cells. The process of wall degeneration is first visible 13 hours after the induction of abscission in a small group of cells found just below the concave groove on the adaxial side of the petiole. As the abscission zone gets progressively weaker the area of cells showing wall breakdown expands, spreading through the parenchyma to the lower side of the stele. The walls of the collenchyma and epidermis along the sides and base of the petiole and the central vascular tissues are the last to break down. Experiments in which the abscission zone was dissected into small pieces were undertaken to investigate whether cell wall hydrolysis was a contagious phenomenon, spreading from cell to cell by direct contact. The results of these investigations indicated that there was little requirement for cell to cell contact in either the temporal or spatial integration of cell wall breakdown.     

STRUCTURAL SPECIALIZATION OF THE SITE OF RESPONSE TO VECTORIAL PHOTO-EXCITATION IN THE SOLAR-TRACKING LEAF OF LAVATERA CRETICA

Structural features of the pulvinus of the solar-tracking leaf of Lavatera cretica L. that are involved in its capacity for omnidirectional and fully reversible bending in response to vectorial excitation of the lamina were studied by light- and scanning electron microscopy. Pulvini that had bent in the plane at right angles to the midvein were bisected along that plane and the symmetrical tissues of the expanded and contracted flanks were compared. The pulvinus contains a central vascular core and exhibits a transversely furrowed exterior. These specialized features enable the fully mature tissue of this region of the petiole to bend reversibly. The epidermis, chlorenchyma, peripheral collenchyma, and cortical parenchyma in the pulvinus form concentric, radially symmetric sheaths around the vascular core and exhibit structural features in their cell walls that would allow considerable changes in cell volume and consequently enable the omnidirectional bending of this pulvinus. Thickened wall portions of the pulvinar epidermis and peripheral collenchyma exhibit a highly specialized architecture, consisting of alternating thick and thin strips, that enhances their flexibility, while maintaining mechanical support. Cell walls of the chlorenchyma and the cortical parenchyma are thin and capable of reversible infolding. Those of the cortical parenchyma also exhibit numerous prominent transverse pit fields, indicative of anisotropic orientation of their microfibrillar lattice transverse to the pulvinar axis. This orientation is compatible with elastic deformation of the cortical parenchyma cells along the pulvinar axis. Filament-like cytoplasmic strands were observed along the walls of pulvinar motor cells, predominantly transverse to the pulvinar axis, but their function (if any) in volume changes of these cells is unknown.     

接骨草的显微结构及其绿原酸组织化学定位研究

运用石蜡切片法和荧光显微镜观察法研究了3个不同接骨草(Sambucus chinensis Lindl.)居群营养器官的显微结构及其绿原酸的分布规律。结果表明:(1)接骨草地上茎厚角组织明显,髓部由大小不等的两类薄壁细胞组成,且有单宁细胞分布;地下根状茎厚角组织细胞小,髓部薄壁细胞大小差异不明显,皮层及髓中有油细胞分布。(2)叶片为异面叶,栅栏组织细胞为短柱状,油细胞不明显。(3)绿原酸分布在根状茎皮层部分细胞、茎厚角组织部分细胞及叶片的海绵组织中,以海绵组织中含量最高。研究认为,髓部薄壁细胞大小的差异可作为接骨草的一个鉴别特征;荧光显微镜观察法可迅速准确显示绿原酸的分布;在所研究的3个接骨草居群中,怀化居群的绿原酸含量最高,若以绿原酸为有效成分来采收接骨草,可以只采收叶。     

Microfibril orientation in plant cell walls

Summary The distribution of particles on the surface of the plasmalemma in the collenchyma of Apium graveolens was studied by the freeze-etching technique. The aim was to determine whether the distribution of particles was related to the known longitudinal or transverse orientation of cellulose microfibrils in different layers of the walls of these cells. Preliminary statistical studies have shown no obvious correlation between particle distribution and microfibril orientation although the distribution appeared uniform rather than random. Qualitatively, the particle distribution on the plasmalemma of differentiating xylem fibres of Eucalyptus maculata and of the cortical parenchyma of Avena sativa coleoptiles appeared to be similar to that observed on the plasmalemma of Apium. No correlation between the particle distribution and the microfibril orientation known to exist in the walls of these cells could be discerned.The orientation of microtubules in the cytoplasm of collenchyma cells of Apium graveolens was parallel to the microfibril orientation in many instances, but exceptions were noted. A possible interpretation for this variation is discussed. It is concluded that the microtubules are the structures which are most likely to be involved in determining microfibril orientation in the cell wall.     

葛(豆科)叶的解剖学研究

利用光学显微镜和扫描电镜观察了葛(Pueraria lobata)叶的解剖学特征。结果表明,葛叶片的上、下表皮都只有一层表皮细胞,上表皮比下表皮厚。上、下表皮都有腺毛和非腺毛。气孔主要分布在下表皮,下表皮的气孔密度为(261±17)mm-2,上表皮只有(6±3)mm-2。叶肉由两层栅栏组织细胞和一层海绵组织细胞构成。叶肉细胞中有丰富的叶绿体。在栅栏组织和海绵组织之间有一层平行于叶脉的薄壁细胞。叶脉中含有大量的草酸钙晶体。葛叶的这些形态特征与其喜阳、耐旱的特点相适应。     

油茶叶肿病子房瘿体和叶片瘿体的形态结构特征观察

采用光学显微镜观察了油茶叶肿病子房瘿体和叶片瘿体的形态特征和组织结构特点。结果表明:(1)油茶叶肿病瘿体是油茶的幼嫩子房和幼叶被细丽外担菌感染后所导致的组织增生而成的,细丽外担菌分布于成熟子房瘿体的外表面和叶片瘿体的表面。(2)子房瘿体由受感染的雌蕊子房增殖而来,成熟后表皮层脱落。(3)子房壁分两层,外层子房壁肉质肥厚,主要由大型薄壁细胞构成,是食用的主要部分,内层子房壁为较薄的心皮层,内外两层子房壁之间具有较大的空隙;心皮内有胚珠,胚珠着生在中轴胎座上,胚珠内部中空而没有育性。(4)叶片瘿体为受感染的幼嫩叶片增殖所致,由大型薄壁细胞构成,瘿体表面具表皮层,成熟后表皮脱落。(5)在正常叶片与叶片瘿体的过渡区内有维管束相通,瘿体侧的厚度比正常叶片厚度增加3～4倍,细胞体积增大5～10倍,但瘿体细胞内无叶绿体。     

Relationships between structure and motility ofAlbizzia motor organs: Changes in ultrastructure of cortical cells during dark-induced closure

Summary Paired leaflets ofAlbizzia julibrissin spread apart (open) in the daytime and fold together (close) at night. We examined the structure of cells in open and closedAlbizzia motor organs (pulvini) to identify reversible changes in structure associated with motility. Pulvini were fixed in glutaraldehyde and stained using conventional methods. The pulvinus has a central vascular cylinder bordered by thick-walled collenchyma cells, in turn surrounded by an endodermis and many layers of cortical parenchyma. Cortical cells in the extensor undergo large changes in shape during leaflet closure linked with: formation of wall infoldings, development of a large periplasmic space filled with fibrils and membranes, development of lobes on the nucleus, evagination of the nuclear outer envelope membrane, break-up of the large central vacuole to form many small vacuoles, and linking of the plasmalemma to inner regions of the cytoplasm by microfilaments. Cortical cells in the flexor, by contrast, remain relatively stable during leaflet movement. Microtubules are present near the plasmalemma in both extensor and flexor cells; in the extensor, spherical coated vesicles are located near the microtubules. The possible function of these structures in regulating intracellular shuttling processes is discussed.     

HISTOLOGICAL STUDIES ON THE COLEOPTILE. I. TISSUE AND CELL TYPES IN THE COLEOPTILE TIP

The uppermost 1-4 mm of 25-mm coleoptiles of oats and wheat have been studied at the optical microscope level, using newer histological methods and sections 1-4 μ thick. The outer epidermal wall, which shows very fine wrinkling, is continuous with the thinner wall of the inner epidermis through the pore. The cells of both epidermal layers have acidophilic cytoplasm with long transvacuolar strands. Both inner and outer epidermis have stomata, those of the outer epidermis having kidney-shaped guard cells like those of dicotyledons. The guard-cell walls are lignified in their inner layers only and are thinly cuticularized. In the vascular bundles the sieve tubes terminate apically about 250 μ below the end of the xylem; the xylem in turn terminates about 400 μ below the extreme apex. A number of clearly undifferentiated cells, with highly basophilic cytoplasm and many mitochondria, separate the xylem elements from the inner epidermis. Towards the outer epidermis there are a few sieve elements, each of which is associated with a special cell having an elongated nucleus supported on fine cytoplasmic strands. The parenchyma of both the tip and the shaft of the coleoptile are generally interpenetrated by air-spaces, but where they are adjacent to the inner epidermis there is heavy interposition of readily stained intercellular material, especially in Triticum. Plastids are widely distributed throughout the tissue, but their greening in light takes place preferentially towards the phloem side of the vascular bundles. The observations are discussed in reference to earlier literature and with regard to the function of the coleoptile as a protecting and guiding organ for the shoot system of the seedling.     

六种沉香属植物叶片解剖结构研究

为比较沉香属不同种植物间的叶片形态解剖特征,将不同来源的六种沉香属植物在海南省兴隆南药园种植,运用石蜡切片法和撕片法对其成熟叶片的解剖特征进行观察,并对叶片的上下表皮,叶脉和叶横切面等12项数量性状进行统计分析。结果表明:六种沉香属植物叶片解剖结构基本一致,均为典型的异面叶,由表皮、叶肉和叶脉组成,表现出典型的旱生形态特点。表皮细胞单层,气孔微下陷,仅分布在下表皮,上下表皮上零星分布着表皮毛。叶肉组织发达,栅栏组织由1~2层排列紧密地圆柱状细胞组成,其间分布着大量的长方晶体,海绵组织内有一层排列较整齐,染色较深的异细胞组成的下皮层。主脉维管束双韧型,呈圆环状,内含大量异细胞。方差分析表明,除栅海比外,叶片厚度、叶脉条数、主脉厚度等其余11项数量指标在六种植物间差异均达到显著水平。聚类分析将这六种植物聚成3类,Aquilaria sinensis(白木香),A.crassna和A.banaensis聚为一类,A.baillonii和A.malaccensis聚为一类;A.yunnanensis(云南沉香)单独为一类。该研究结果为沉香属植物的物种鉴定提供了解剖学依据,同时对沉香属植物合理开发利用具有重要意义。     

白鲜营养器官解剖结构及其与白鲜碱的积累关系

应用植物解剖学、组织化学及植物化学方法对白鲜营养器官根、茎、叶的结构及其生物碱的积累进行了研究。结果显示:(1)白鲜根的次生结构以及茎和叶的结构类似一般双子叶植物;白鲜多年生根主要由周皮、次生韧皮部、维管形成层以及次生木质部组成,根次生韧皮部中可见大量的淀粉、草酸钙簇晶、韧皮纤维以及油细胞;茎由表皮、皮层、维管组织和髓组成;叶由表皮、栅栏组织、海绵组织和叶脉组成;在茎和叶初生韧皮部的位置均分布有韧皮纤维,在叶表皮上分布有头状腺毛和非腺毛;在茎和叶紧贴表皮处分布有分泌囊。(2)组织化学分析结果显示:在白鲜多年生根中,生物碱类物质主要分布在周皮、次生韧皮部、维管形成层和木薄壁细胞中;在茎中,生物碱主要分布在表皮、皮层、韧皮部、木薄壁细胞及髓周围薄壁细胞中;在叶中,生物碱主要分布在表皮细胞、叶肉组织和维管组织的薄壁细胞;此外在分泌囊和头状腺毛中亦含有生物碱类物质。(3)植物化学结果显示,秦岭产白鲜根皮/白鲜皮、根木质部、茎和叶中白鲜碱含量分别为0.041%、0.012%、0.004%和0.002%,其中木质部中白鲜碱含量和其他部分地区白鲜皮中白鲜碱含量类似。研究表明,在秦岭产白鲜营养器官中,除根皮/白鲜皮外,在根木质部亦含有大量的白鲜碱,且在茎和叶中亦含有一定的白鲜碱,具有潜在的开发利用价值。     

Immunolocalization of LeAGP-1, a modular arabinogalactan-protein, reveals its developmentally regulated expression in tomato

 Arabinogalactan-proteins (AGPs) are highly glycosylated cell surface proteins that are thought to function in plant growth and development. The developmentally regulated expression of LeAGP-1, a novel and major AGP in tomato, was examined in different organs and tissues of tomato (Lycopersicon esculentum Mill. cv. UC82B) plants with an anti-peptide antibody (i.e. the PAP antibody) directed specifically against the lysine-rich subdomain of the LeAGP-1 core protein. During cell differentiation in tomato plants, LeAGP-1 was associated with cell wall thickening and lignification of particular cell types. Specifically, LeAGP-1 was detected in secondary wall thickenings of maturing metaxylem and secondary xylem tracheary elements in roots and stems, and in thickened cell walls of phloem sieve elements. However, LeAGP-1 was also present in thin-walled, cortical parenchyma cells of seedling roots as well as thick-walled collenchyma cells in young stems, both of which are not lignified. Based on these observed patterns, possible roles for LeAGP-1 in plant growth and development are discussed. Received: 17 August 1999 / Accepted: 7 October 1999     

中华白花丹参与其近缘种的形态分类鉴定

该研究采用光学显微镜和扫描电镜相结合的方法,对中华白花丹参(Salvia sinealba)与其近缘种丹参(S.miltiorrhiza)及山东丹参(S.shandongensis)根的解剖学、叶表皮、花及花粉粒进行了系统地比较研究。结果表明:中华白花丹参(S.sinealba)根的中央部位有多数薄壁细胞,在根横切面射线薄壁细胞间及韧皮部外侧与次生皮层部位有多数裂隙;叶片上表皮细胞外平周壁具有细密平行丝状褶皱(SEM);花冠白色;花粉粒椭圆形,外壁具网状雕纹,网眼较大,多角形,少为单穿孔。上述这些显著的特征,不仅为中华白花丹参在植物分类学上的地位提供了形态解剖学依据,而且为近缘种丹参及山东丹参的分类鉴定提供了佐证,同时也为中华白花丹参这一特有新资源的保护和开发利用提供了资料。     

THE EFFECTS OF MECHANICAL STIMULATION AND ETIOLATION ON THE COLLENCHYMA OF DATURA STRAMONIUM

Walker , Waldo S. (Grinnell College, Grinnell, Iowa.) The effects of mechanical stimulation and etiolation on the collenchyma of Datura stramonium. Amer. Jour. Bot. 47(9) : 717–724. Illus. 1960.–In an effort to determine the effect of mechanical stimulation on collenchyma tissue, plants of Datura stramonium L. were placed on a mechanical agitator and subjected to intensive shaking for 9 hr. per day for 40 days. Measurements indicated that such stimulation greatly increased the amount of wall thickening per cell, as observed in transverse section. Measurements also indicated that such stimulation may inhibit collenchyma cell elongation. A second group of Datura stramonium plants was placed in total darkness to determine the effect of such treatment on the quantity of wall thickening in the collenchyma tissue. Measurements indicated that when plants were placed in the dark for extended periods a great reduction of wall thickening resulted. It is suggested that reduction of wall material was due to its utilization as substrate for respiratory processes which occur in the plant under such extreme conditions. The composition and structure of the collenchyma cell walls are discussed.     

Comparison of expression of three different sub-cellular targeted GFPs in transgenic Valencia sweet orange by confocal laser scanning microscopy

The green fluorescent protein (GFP) has become an ideal visual marker to monitor and quantify the expression of the transgene. It can be targeted to specific subcellular locations, including the endoplasmic reticulum, mitochondria, actin cytoskeleton and nuclei through the addition of signal peptides. Our previous work has resulted in transgenic citrus plants expressing cytoplasmic targeted GFP (Cy-GFP) or endoplasmic reticulum targeted GFP (Er-GFP) gene. To evaluate the localization of three different subcellular targeted GFP, i.e., Cy-GFP, Er-GFP and mitochondria targeted GFP (Mt-GFP) in citrus tissues and to utilize cell lines containing Mt-GFP for basic research in cell fusion, the plasmid pBI-mgfp4-coxIV encoding the Mt-GFP gene was successfully transferred into embryogenic callus of Valencia sweet orange (Citrus sinensis (L.) Osbeck) via Agrobacterium tumefaciens-mediated transformation. Furthermore, we compared the specific expression of these three different subcellular localized GFP constructs in cells of different mature leaf tissues (upper epidermis, palisade parenchyma, spongy parenchyma and lower epidermis) by a confocal laser scanning microscope (CLSM). Cytoplasmic-localized GFP expression was observed throughout the cytoplasm but appeared to accumulate within the nucleoplasm. The Er-GFP occurred within a layer very close to the cell wall. In addition, a stable fluorescence on the ER network throughout the guard cells was detected. Interestingly, the Mt-GFP specifically expressed in the guard cells to particles of about 1–2 μm within the cytoplasm in this case. To verify that the fluorescent particles observable in the guard cells are indeed mitochondria, we co-localize the Mt-GFP fusion protein with a mitochondrial-specific dye in citrus protoplasts. These results demonstrate that the subcellular distribution of the three subcellular targeted GFP is very distinct in citrus leaf cells and the cell lines containing Mt-GFP gene can be further used in citrus basic cell fusion research.     

Morphological and anatomical characteristics and taxonomical significance of achene micromorphology of Achillea phrygia and A. gypsicola (Asteraceae), endemic to Turkey

Micromorphological and anatomical characters of two Achillea L. species, A . phrygia Boiss. & Bal. and A. gypsicola Hub-Mor., which are endemic to Turkey, were investigated. It was observed that stem length, corymb width, number of capitula and median phyllary shape were diagnostic characters. In the anatomical studies, cross sections were taken from roots, stem and leaves. It was observed that roots of the investigated taxa had a secondary thickening. Endodermis and collenchyma layers were prominent in the stem of both taxa and they had a bifacial mesophyll while the layers of the mesophyll varied. Stomata were anomocytic in both species. We found that there was a significant difference in terms of width of epidermis cells and length of cortex cells in the root, epidermis width and length, collenchyma and parenchyma cells, endodermis length, diameter of trachea of stem, length of upper epidermis cells, width of lower epidermis cells, length of palisade parenchyma and spongy parenchyma cells, diameter of trachea and stomata length of leaf between the two taxa (p<0.05). Scanning electron microscopy (SEM) was used to describe the micromorphology of trichomes and achenes. In A. phrygia , long and eglandular trichomes were more dense on the stem and leaf epidermis. Achene micromorphological characteristics such as size, shape and achene coat were considered to be useful in separating the investigated species.     

SECONDARY PULVINUS OF ROBINIA PSEUDOACACIA (LEGUMINOSAE): STRUCTURAL AND ULTRASTRUCTURAL FEATURES

The structure of the secondary pulvinus of Robinia pseudoacacia has been examined together with ultrastructural features of motor cells both in open and closed pulvini, to identify ultrastructural changes associated with leaflet movement. Pulvini have a central vascular core bordered by thick-walled collenchyma cells, which in turn are surrounded by several layers of cortical parenchyma cells. Cortical motor cells exhibit ultrastructural features similar to those reported in homologous cells of other pulvini. The vacuolar compartment contains two kinds of vacuoles: nontannin vacuoles, which change both in number and size during leaflet movement, and tannin vacuoles, which may act as an ion reservoir. No differences in wall thickness were found between flexor and extensor motor cells. Thick walls of collenchyma cells show numerous pits with plasmodesmata through which the phloem parenchyma cells and the inner cortical motor cells are connected. Tannin vacuoles and calcium oxalate crystals are common inclusions of phloem parenchyma cells. The tissue arrangement and the occurrence of pits with plasmodesmata in the central cylinder cells provide evidence of symplastic continuity through the central cylinder between the extensor and flexor regions of the motor organs. The greater amplitude of Robinia leaflet movements may be related to the extension of motor regions, the scarcity of lignification in the central vascular core, and the thin flexor walls.     

The ontogeny and structure of the pericarp and seed-coat of Harpephyllum caffrum Bernh. ex Krauss (Anacardiaceae)

The exocarp sensu lato , which develops from the outer epidermis and adjacent parenchyma of the ovary wall, consists of collenchyma cells with a stomatous epidermis. The fleshy, parenchymatous mesocarp or sarcocarp develops after endocarp differentiation. The endocarp is partly spongy and partly woody. The spongy endocarp contains most of the vascular tissue and fills the cavities and grooves of the intricately sculptured outer woody endocarp. The inner woody endocarp and adjacent woody, endocarpal operculum develop from the inner epidermis and subepidermal parenchyma of the ovary wall. The bitegmic, anatropous ovule develops into a derived, exalbuminous seed with an undifferentiated seed-coat. An extensive chalaza, extensive hypostase sensu lato and the raphe are important in the development of the seed-coat. The pericarp and seed-coat of H. caffrum is compared with those of Sclerocarya birrea subsp. caffra and Lannea discolor . The close phylogenetic relationship of these three species of the Spondieae is reaffirmed. The marked similarities in pericarp and seed structure between H. caffrum and species of the genus Spondias are noted.     

Pericarp histogenesis and histochemistry during fruit development in Butia capitata (Arecaceae)

Palm fruits show great structural complexity, and in-depth studies of their development are still scarce. This work aimed to define the developmental stages of the fruit of the neotropical palm Butia capitata and to characterize the ontogenesis of its pericarp. Biometric, anatomical, and histochemical evaluations were performed on pistillate flowers and developing fruits. The whole fruit develops in three phases: (I) histogenesis (up to 42 days after anthesis – DAA), when the topographic regions of the pericarp are defined; (II) pyrene maturation (42 to 70 DAA), when the sclerified zone of the pericarp is established; and (III) mesocarp maturation (70 to 84 DAA), when reserve deposition is completed. During pericarp ontogenesis (i) the outer epidermis and the outer mesophyll of the ovary give origin to the exocarp (secretory epidermis, collenchyma, parenchyma, sclerenchyma, and vascular bundles); (ii) the median ovarian mesophyll develops into the mesocarp, with two distinct topographical regions; (iii) the inner ovarian epidermis originates the endocarp; and in the micropylar region, it differentiates into the germination pore plate, a structure that protects the embryo and controls germination. (iv) Most of the inner region of the mesocarp fuses with the endocarp and, both lignified, give rise to the stony pyrene; (v) in the other regions of the mesocarp, carbohydrates and lipids are accumulated in a parenchyma permeated with fiber and vascular bundles. The development of the B. capitata pericarp presents high complexity and a pattern not yet reported for Arecaceae, which supports the adoption of the Butia-type pyrenarium fruit class.