Vascular system of the floret of Alopecurus carolinianus (Gramineae)

1987 ◽  
Vol 65 (12) ◽  
pp. 2592-2600 ◽  
Author(s):  
Thompson Demetrio Pizzolato
Keyword(s):  
Vascular System ◽  
Sieve Tube ◽  
Sieve Element ◽  
Sieve Elements

The interconnecting vascular system of the floret of Alopecurus carolinianus Walter begins as a single, collateral bundle, which enters the rachilla and becomes reorganized into a diarch pattern while ascending between the glumes. During a pronounced posterior enlargement, the rachilla bundle becomes connected with the median and four lateral bundles of the lemma. Above the trace to the lemma median, elements of a xylem discontinuity surrounded by those of a sieve-element plexus form in the rachilla bundle. Higher, a trace consisting of elements of the xylem discontinuity and the plexus enters the anterior and the posterior stamen. Two bundles, the lowest portion of the pistil vasculature, rise eccentrically from the xylem discontinuity and sieve-element plexus at the level of the stamen traces. The bundles condense into one which rotates counterclockwise and connects with the anterior sieve tube of the pistil. The xylem discontinuity of the bundle now in the pistil begins to diminish, and the sieve elements fan out to the sides and posterior of the xylem discontinuity. From the sieve elements one or two posterolaterals emerge toward the styles. The bundle of diffuse sieve elements in a semicircle behind the diminishing xylem discontinuity is now the placental bundle of the pistil. After its xylem discontinuity and then its sieve elements fade out, the placental bundle merges with the ovule at the chalaza.

Vascular system of the floret of Phleum pratense

1988 ◽  
Vol 66 (9) ◽  
pp. 1818-1829 ◽  
Author(s):  
Thompson Demetrio Pizzolato
Keyword(s):  
Vascular Tissue ◽  
Vascular System ◽  
Sieve Tube ◽  
Sieve Element ◽  
Phleum Pratense ◽  
Tracheary Elements ◽  
Sieve Elements ◽  
Circular Component

Two bundles occur in the rachilla at the floret base. The anterior bundle supplies the vascular tissue for the lemma median trace, and the posterior supplies that for its two extreme laterals. The intermediate laterals of the lemma connect at the anterior bundle, and the two palea traces join near the posterior bundle to the traces for the extreme lemma laterals. Near these connections sieve elements of the two rachilla bundles link, forming the lower component of the sieve-element plexus. The xylem discontinuity begins above the anterior bundle. An upper, circular component of the sieve-element plexus surrounds the discontinuity. The sieve elements of the lodicules join the anterior of the upper plexus. The upper plexus becomes trilobed as it merges with the stamen traces. Three pistil bundles including sieve elements and tracheary elements of the xylem discontinuity join the upper plexus. These pistil bundles unite into a circular pistil plexus surrounding the discontinuity. The anterior sieve tube of the pistil joins the anterior of the pistil plexus. Sieve elements emerge from the posterolateral portions of the plexus toward the styles and leave a placental bundle of sieve elements and tracheary elements of the xylem discontinuity in the pistil posterior.

Vascular system of the fertile floret of Phalaris arundinacea

1989 ◽  
Vol 67 (5) ◽  
pp. 1366-1380 ◽  
Author(s):  
Thompson Demetrio Pizzolato
Keyword(s):  
Vascular System ◽  
Lower Layer ◽  
Phalaris Arundinacea ◽  
Sieve Element ◽  
Vascular Bundles ◽  
Tracheary Elements ◽  
Sieve Elements

Six vascular bundles lie in two rows of three in the rachilla at the base of the fertile floret. Each bundle relates to a lemma or palea trace. As the rachilla bundles become traces they also produce sieve elements that interconnect to form the lower layer of the sieve-element plexus. Lodicule traces join the anterior of this lower plexus. Only the tracheary elements from the rachilla bundle related to the lemma's median trace rise higher in the rachilla, and these merge into a system of anomalous tracheary elements (xylem discontinuity) that rises toward the ovule. The lower sieve-element plexus layer ascends around the xylem discontinuity into a trilobed upper plexus layer which supplies the stamen traces. A third sieve-element plexus (pistil plexus) joins the upper plexus layer by three descending prongs. The pistil plexus, which occurs at the base of the pistil, is linked on its anterior to the anterior bundle. The placental bundle rises from the posterior of the pistil plexus and furnishes the sides of the pistil with their anterolateral and posterolateral sieve elements. The posterolaterals supply the styles. The sieve elements and the xylem discontinuity of the placental bundle supply the ovule.

scholarly journals Ultrastructural changes in aster yellows phytoplasma affected Limonium sinuatum Mill. plants.I Pathology of conducting tissues

2014 ◽  
Vol 70 (3) ◽  
pp. 173-180 ◽  
Author(s):  
Anna Rudzińska-Langwald ◽  
Maria Kamińska
Keyword(s):  
Endoplasmic Reticulum ◽  
Structural Changes ◽  
Sieve Tube ◽  
Sieve Element ◽  
Ultrastructural Changes ◽  
Sieve Elements ◽  
Aster Yellows ◽  
Parenchyma Cells ◽  
Sieve Tubes ◽  
Aster Yellows Phytoplasma

Changes in anatomy and cytology of conducting tissues of <em>Limonium sinuatum</em> Mill. plants affected by aster yellows phytoplasma were investigated. In the phloem tissues of affected plants stem necrosis takes place. In necrotic regions no sieve tubes were observed only necrotic cells and parenchyma cells. The sieve tubes present on the border of necrosis showed collapsed walls and were rich in vesicles. Phytoplasma cells were observed in sieve tubes present in nonnecrotic regions of the phloem. Various structural changes in sieve elements were investigated. The endoplasmic reticulum cistemae were often localised in the lumen of the sieve element without contact with the walls. Such localisation of endoplasmic reticulum was never observed in healthy plants. Vesicles of different size, fuzzy material and clumping of p-proteins were characteristic for sieve elements from nonnecrotic part of phloem. No correlation with the sieve tube structure and the appearance of phytoplasma in a single sieve element was found. In control plants of <em>L. sinuatum</em> phloem observed were phloem parenchyma cells with spiny vesicles (SV). In infected plants there were a remarkable increase in cells with SV. Also the SV itself had not only a vesicular but also a tubular or extended cistern shape.

Proteins in the sieve element-companion cell complexes: their detection, localization and possible functions

2000 ◽  
Vol 27 (6) ◽  
pp. 489 ◽  
Author(s):  
Hiroaki Hayashi ◽  
Akari Fukuda ◽  
Nobuo Suzui ◽  
Shu Fujimaki
Keyword(s):  
Sieve Tube ◽  
Soluble Proteins ◽  
Sieve Element ◽  
Tissue Extract ◽  
Companion Cell ◽  
Phloem Sap ◽  
Sieve Elements ◽  
Cell Complexes ◽  
Companion Cells ◽  
Sieve Tubes

Many kinds of proteins have been found in the sieve element–companion cell complexes by the analyses of phloem sap and microscopic observations. The cDNAs, which encode some of these sieve-tube proteins, have already been cloned. As mature sieve elements lack nuclei and most ribosomes, sieve-tube proteins have been hypothesized to be synthesized in the companion cells and then transported to the lumina of the functional sieve tubes through the plasmodesmata connecting the companion cells and sieve elements. Soluble proteins present in the sieve tubes can be collected by several techniques, such as incision or the aphid technique. The composition of the proteins in the phloem sap is unique compared with that of tissue extract, suggesting these proteins have important roles for the development and functions of sieve tubes.

scholarly journals A STUDY OF SIEVE ELEMENT STARCH USING SEQUENTIAL ENZYMATIC DIGESTION AND ELECTRON MICROSCOPY

1970 ◽  
Vol 45 (2) ◽  
pp. 383-398 ◽  
Author(s):  
Barry A. Palevitz ◽  
Eldon H. Newcomb
Keyword(s):  
Electron Microscopy ◽  
Sieve Tube ◽  
Cell Types ◽  
Enzymatic Digestion ◽  
Sieve Element ◽  
Branch Points ◽  
Thin Sections ◽  
Sieve Elements ◽  
Hypocotyl Tissue ◽  
Bare Copper

The fine structure of plastids and their starch deposits in differentiating sieve elements was studied in bean (Phaseolus vulgaris L.). Ultrastructural cytochemistry employing two carbohydrases specific for different linkages was then used to compare the chemical nature of "sieve tube starch" (the starch deposited in sieve elements) with that of the ordinary starch of other cell types. Hypocotyl tissue from seedlings was fixed in glutaraldehyde, postfixed in osmium tetroxide, and embedded in Epon-Araldite. Treatment of thin sections on uncoated copper grids with α-amylase or diastase at pH 6.8 to cleave α-(1 → 4) bonds resulted in digestion of ordinary starch grains but not sieve element grains, as determined by electron microscopy. Since α-(1 → 6) branch points in amylopectin-type starches make the adjacent α-(1 → 4) linkages somewhat resistant to hydrolysis by α-amylase, other sections mounted on bare copper or gold grids were treated with pullulanase (a bacterial α-[1 → 6] glucosidase) prior to digestion with diastase. Pullulanase did not digest sieve element starch, but rendered the starch digestible subsequently by α-amylase. Diastase followed by pullulanase did not result in digestion. The results provide evidence that sieve element starch is composed of highly branched molecules with numerous α-(1 → 6) linkages.

scholarly journals A crystalline inclusion in sieve element nuclei of Amsinckia. II. The inclusion in maturing cells

1979 ◽  
Vol 38 (1) ◽  
pp. 11-22
Author(s):  
K. Esau ◽  
A.C. Magyarosy
Keyword(s):  
Hydrostatic Pressure ◽  
Sieve Element ◽  
Crystalline Inclusion ◽  
Sieve Elements ◽  
P Protein ◽  
Sudden Release ◽  
Sieve Plates ◽  
Tubular Components

The compounds crystalloids formed in sieve element nuclei of Amsinckia douglasiana A. DC. (Boraginaceae) during differentiation of the cell become disaggregated during the nuclear breakdown characteristic of a maturing sieve element. The phenomenon occurs in both healthy and virus-infected plants. The crystalloid component termed cy, which is loosely aggregated, separates from the densely aggregated component termed cx and disperses. The cx component may become fragmented, or broken into large pieces, or remain intact after the cell matures. After their release from the nucleus both crystalloid components become spatially associated with the dispersed P-protein originating in the cytoplasm, but remain distinguishable from it. The component tubules of P-protein are hexagonal in transections and are somewhat wider than the 6-sided cy tubules. The cx tubules are much narrower than the P-protein or the cy tubules and have square transections. Both the P-protein and the products of disintegrated crystalloids accumulate at sieve plates in sieve elements subjected to sudden release of hydrostatic pressure by cutting the phloem. The question of categorizing the tubular components of the nuclear crystalloid of a sieve element with reference to the concept of P-protein is discussed.

The secondary phloem of Austrobaileya scandens

1970 ◽  
Vol 48 (2) ◽  
pp. 341-359 ◽  
Author(s):  
Lalit M. Srivastava
Keyword(s):  
Tannic Acid ◽  
Cross Sections ◽  
Significant Proportion ◽  
Sieve Tube ◽  
Secondary Phloem ◽  
Sieve Elements ◽  
Sieve Cells ◽  
Companion Cells ◽  
Parenchyma Cells ◽  
Definition Of

The origin of sieve elements and parenchyma cells in the secondary phloem of Austrobaileya was studied by use of serial cross sections stained with tannic acid – ferric chloride and lacmoid. In three important respects, Austrobaileya phloem recalls gymnospermous features: it has sieve cells rather than sieve-tube members; a significant proportion of sieve elements and companion cells arise independently of each other; and sieve areas occur between sieve elements and companion cells ontogenetically unrelated to each other. The angiospermous feature includes origin of most sieve elements and parenchyma, including companion cells, after divisions in phloic initials. In these instances companion cells show a closer ontogenetic relationship to sieve elements than do other parenchyma cells. The combination of gymnospermous and angiospermous features makes phloem of Austrobaileya unique when compared to that of all those species that have been investigated in detail. It is further suggested that the term albuminous cells is inappropriate and should be replaced by companion cells but that the ontogenetic relationship implicit in the definition of companion cells is too restrictive and should be abandoned.

Anatomy and ultrastructure of the endophytic system of Pilostyles thurberi (Rafflesiaceae)

1985 ◽  
Vol 63 (7) ◽  
pp. 1231-1240 ◽  
Author(s):  
Job Kuijt ◽  
D. Bray ◽  
A. R. Olson
Keyword(s):  
Cell Types ◽  
Sieve Element ◽  
Cell Type ◽  
Discontinuous System ◽  
Sieve Elements ◽  
The Third ◽  
Sieve Plates ◽  
Host Parasite ◽  
Anatomy And Ultrastructure ◽  
Sieve Pores

The endophytic system of Pilostyles thurberi Gray consists of initially uniseriate filaments which develop into an anastomosing complex of larger cortical strands and radial sinkers. In the cortical strands three cell types are recognized, two of which differ largely in the density of the cytoplasm, the shape of the nucleus, and the degree to which the cytoplasm becomes plasmolyzed during fixation. The nuclei of both cell types contain two nucleoli which are physically connected by a nucleolar bridge. The third cell type demonstrates sieve plates, including a calloselike substance in the sieve pores and is consequently considered to be a sieve element. The sieve elements appear to form a discontinuous system and are regarded as a vestigial cell type. Plasmodesmal connections across the host–parasite interface have not been observed.

scholarly journals Anatomical features of conductive tissues of soybeans that prevent the penetration of pathogenic agents of bacterial blight into seeds

2021 ◽  
Vol 188 (4) ◽  
pp. 25-34
Author(s):  
S.V. Zelentsov ◽  
◽  
G.M. Saenko ◽  
E.V. Moshnenko ◽  
◽  
...  
Keyword(s):  
Bacterial Blight ◽  
Pathogenic Bacteria ◽  
Vascular System ◽  
Sieve Tube ◽  
Soybean Seeds ◽  
Oil Crops ◽  
Russian Research Institute ◽  
Sieve Plates ◽  
Soybean Leaves ◽  
Pathogenic Agents

The ways of penetration of pathogenic bacteria from the infected vegetative parts of plants into soybean seeds remain practically unexplored. It is widely believed that soybean seeds are infected through the vascular system from already infected areas of the vegetative parts. The aim of the present research was to study the possibility of penetration of pathogens of bacterial blight into soybean seeds through the conductive tissues of plants. The studies were carried out in 2019–2021 in V.S. Pustovoit All-Russian Research Institute of Oil Crops on plants and seeds of soybean variety Vilana. It was found that the size of stomatal slots in soybean leaves is 8–12 µm. This ensures free penetration of bacteria with a diameter of 1.3–1.7 µm into the leaf mesophyll. The pore sizes of the sieve plates of the phloem range from 0.4–0.7 to 0.8–1.6 µm, depending on the age of the plants. The largest pores of the phloem sieve plates are comparable to the diameters of pathogenic bacteria. However, a large number of transverse sieve plates located in the vessels of the phloem every 0.05–0.1 mm will filter and partially retain bacteria in each sieve tube along the path of cell sap in the phloem. Therefore, the pathogenic bacteria passing through the entire phloem from leaves infected with bacteriosis up to pods is physically unlikely. In pods, the vascular system ends in the area of attachment of the placenta to the seed hilum. In the hilum, there are no conductive tissues, and the further flow of water and nutrients into the seed is carried out diffusely through the plasmodesma of cell walls. It was found that the anatomical structure of the soybean phloem prevents the free movement of pathogenic bacteria along the conductive system directly into the inner tissues of the seeds. Therefore, the hypothesis of infection of soybean seeds with pathogens of bacterial blight through the conducting system of the plant should be considered untenable

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