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.

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.

Fine structure of the phloem of Pisum sativum. I. The sieve element ontogeny

1965 ◽  
Vol 13 (2) ◽  
pp. 171 ◽  
Author(s):  
MC Wark ◽  
TC Chambers
Keyword(s):  
Endoplasmic Reticulum ◽  
Pisum Sativum ◽  
Nuclear Material ◽  
Sieve Element ◽  
Secondary Phloem ◽  
Sieve Elements ◽  
Pisum Sativum L ◽  
Ontogenetic Study ◽  
Sieve Plates ◽  
Peripheral Cytoplasm

An ontogenetic study of secondary phloem sieve elements of Pisum sativum L., fixed on the intact plant for electron microscopy, indicates that the connecting strands across the sieve plates are continuities of the endoplasmic reticulum. Each connecting strand is surrounded by a callose cylinder. The peripheral cytoplasm of the nucleate "young" sieve elements contains longitudinally oriented tubules of endoplasmic reticulum. As the sieve elements develop, nuclear material is extruded into the cytoplasm by way of a fibrotubular body which is structurally distinct from the slime body. When the cells are fully expanded the slime bodies disperse. This process is followed by breakdown of a number of organelles including the nucleus and tonoplast. This apparently leaves the endoplasmic reticulum free in the cell lumen.

A crystalline inclusion in sieve element nuclei of Amsinckia. I. The inclusion in differentiating cells

1979 ◽  
Vol 38 (1) ◽  
pp. 1-10
Author(s):  
K. Esau ◽  
A.C. Magyarosy
Keyword(s):  
Sieve Element ◽  
Entire Length ◽  
The Other ◽  
Crystalline Inclusion ◽  
Sieve Elements

The presence of usually single, elongated, compound crystalloids in nuclei of sieve elements is an outstanding characteristic of the phloem of Amsinckia douglasiana A. DC. (Boraginaceae). The crystalloid consists of two components forming alternating panels, or blocks, that extend through the entire length of the crystalloid and radiate from the centre where one of the components predominates. Three to seven panels for each component were recorded. One component consists of 4-sided tubules closely packed in highly ordered aggregates, the other of wider 6-sided tubules rather loosely arranged in paracrystalline aggregates. The crystalloid arises at the beginning of sieve element differentiation. Aggregates of 4-sided tubules appear first. In plants infected with the curly top virus, the crystalloids do not differ from those in non-infected controls in structure and conformation. But because the phloem in infected plants is hyperplastic, with most of the cells differentiating as sieve elements, the crystalloids are far more abundant in diseased than in healthy plants.

Nuclear Crystalloids in Sieve Elements of Species of Echium (Boraginaceae)

1982 ◽  
Vol 54 (1) ◽  
pp. 149-160
Author(s):  
KATHERINE ESAU ◽  
JENNIFER THORSCH
Keyword(s):  
Protein A ◽  
Sieve Element ◽  
Crystalline Form ◽  
Two Dimensional ◽  
Common Component ◽  
Dimensional Lattice ◽  
Sieve Elements ◽  
Ultrastructural Studies ◽  
P Protein ◽  
Systematic Character

Ultrastructural studies of differentiating phloem of the midvein in 15 species of Echium (Boraginaceae) have shown that in every species one or more crystalloids develop in sieve-element nuclei. These inclusions appear as soon as the cell begins to differentiate from a procambial derivative. Small at first, they enlarge later, particularly in length. The crystalloid may extend end-to-end in the correspondingly elongated nucleus. When the nucleus disintegrates in the maturing cell the crystalloid is released into the cell lumen where it remains intact or becomes fractured into large pieces. No dissociation into subunits was observed. The crystalloids are composed of tightly packed narrow rods (tubules) forming a two-dimensional lattice of squares in transections and a system of parallel striations in longitudinal sections. The similarities of these inclusions to the crystalline form of P-protein in Fabaceae raises the question of terminological delimitation of P-protein, a common component of angiospermous sieve-element protoplasts. The occurrence of nuclear crystalloids in another previously investigated genus in the Boraginaceae, Amsinckia, suggests that this inclusion should be explored in boraginaceous representatives for its possible value as a systematic character.

scholarly journals TUBULAR AND FIBRILLAR COMPONENTS OF MATURE AND DIFFERENTIATING SIEVE ELEMENTS

1967 ◽  
Vol 34 (3) ◽  
pp. 801-815 ◽  
Author(s):  
James Cronshaw ◽  
Katherine Esau
Keyword(s):  
Light And Electron Microscopy ◽  
Protein Body ◽  
Sieve Element ◽  
Protein Component ◽  
Sieve Plate ◽  
Sieve Elements ◽  
P Protein ◽  
Ontogenetic Study ◽  
P2 Protein ◽  
Fibrillar Component

An ontogenetic study of the sieve element protoplast of Nicotiana tabacum L. by light and electron microscopy has shown that the P-protein component (slime) arises as small groups of tubules in the cytoplasm. These subsequently enlarge to form comparatively large compact masses of 231 ± 2.5 (SE)A (n = 121) tubules, the P-protein bodies. During subsequent differentiation of the sieve element, the P-protein body disaggregates and the tubules become dispersed throughout the cell. This disaggregation occurs at about the same stage of differentiation of the sieve elements as the breakdown of the tonoplast and nucleus. Later, the tubules of P-protein are reorganized into smaller striated 149 ± 4.5 (SE)A (n = 43) fibrils which are characteristic of the mature sieve elements. The tubular P-protein component has been designated P1-protein and the striated fibrillar component P2-protein. In fixed material, the sieve-plate pores of mature sieve elements are filled with proteinaceous material which frays out into the cytoplasm as striated fibrils of P2-protein. Our observations are compatible with the view that the contents of contiguous mature sieve elements, including the P-protein, are continuous through the sieve-plate pores and that fixing solutions denature the proteins in the pores. They are converted into the electron-opaque material filling the pores.

Protein Component in Sieve Elements of Quercus Rubra L.

1976 ◽  
Vol 34 ◽  
pp. 40-41
Author(s):  
Lidija Murmanis
Keyword(s):  
Quercus Rubra ◽  
Sieve Element ◽  
Protein Component ◽  
Sieve Elements ◽  
P Protein ◽  
Intimate Association ◽  
Rough Er ◽  
Differentiation Stage ◽  
Oriented Parallel ◽  
Stage 1

At the earliest stage, P-protein in red oak sieve elements can be identified with the fine filaments embedded in the cytoplasm (Fig. 1), and they appear similar to the P-protein component in Cucurbita maxima at an early differentiation stage (1). At this time ribosomes (in a spiral configuration) and the rough ER are numerous and in intimate association with the filaments. As differentiation proceeds P-protein bodies are formed in which the filaments are randomly arranged (Fig. 2). Later the filaments become oriented parallel to one another (Fig. 1, at right) and are transformed structurally into tubules. Tubules aggregate into crystalline bodies (Figs. 3, 4) which resemble extruded nucleoli reported previously (2, 3). Individual tubules have a diameter of about 235A and a tripartite structure--60-70A thick electron-dense walls separated by an electron-transparent core. During the disintegration of sieve element protoplast the crystalline bodies disperse and tubules gradually change into fibrils.

Nuclear crystalloids in sieve elements of Boraginaceae: a protein digestion study

1983 ◽  
Vol 64 (1) ◽  
pp. 37-47
Author(s):  
J. Thorsch ◽  
K. Esau
Keyword(s):  
Proteolytic Enzymes ◽  
Differential Response ◽  
Sieve Element ◽  
Enzyme Digestion ◽  
The Other ◽  
Sieve Plate ◽  
Protein Digestion ◽  
Sieve Elements ◽  
P Protein ◽  
Parallel Arrangement

Nuclear crystalloids have been found in sieve elements of several Boraginaceae. Nuclei of differentiating sieve elements of Echium and other genera except Amsinckia contain one or more crystalloids composed of thin rods densely packed in parallel arrangement. After the nuclei disintegrate in the maturing sieve element the crystalloids are released into the cell lumen where they persist intact. In Amsinckia the crystalloid consists of two components: a dense component, similar to the crystalloid in the other genera and a loosely arranged paracrystalline component. The proteinaceous nature of the nuclear crystalloids and their possible similarity to P-protein was investigated by enzyme digestion techniques. Three proteolytic enzymes were employed in this study: protease, pepsin and trypsin. Successful digestion of the dense crystalloid in both Echium and Amsinckia was obtained with each enzyme tested. P-protein plugging the sieve plate pores was also digested. The loose component in Amsinckia and the aggregated and dispersed P-protein were not affected by the enzyme digestion procedures. These results seemed to indicate that the density or compactness of the proteinaceous inclusions may play a role in the differential response.

An Ultrastructural Study of the Phloem of Drimys (Winteraceae)

IAWA Journal ◽  
1985 ◽  
Vol 6 (3) ◽  
pp. 255-268 ◽  
Author(s):  
Jennifer Thorsch ◽  
Katherine Esau
Keyword(s):  
Endoplasmic Reticulum ◽  
Ultrastructural Study ◽  
Protein Body ◽  
Sieve Element ◽  
Companion Cell ◽  
Young Cell ◽  
P Protein ◽  
Companion Cells ◽  
Protein Granules ◽  
Sieve Plates

The ultrastructural features of mainly primary phloem of three species of Drimys (Winteraceae), D. winteri J. R. ' G. Forst., D. lanceolata (Poiret) Baill. and D. granadensis L. f. var. mexicana (DC.) A. C. Smith are similar to those usually observed in dicotyledons. The sieve element is early discernible by its association with a companion cell, the deposition of callose in nascent sieve areas, and the appearance in the cytoplasm of the nondispersing paracrystalline protein body. Plastids with starch (and in D. lanceolata also with paracrystalline protein granules), mitochondria, sparse endoplasmic reticulum cisternae (ER), dictyosomes, and ribosomes are present in the young cell. Stacking of ER was not conspicuous. The nucleus is moderately chromatic before its breakdown. P-protein occurs in more or less dense aggregates that usually become dispersed after the tonoplast disappears. The subunits of the P-pro tein have tubular structure before the dispersal. The plasmalemma is retained. The sieve areas are combined into sieve plates on long radial walls and on some transverse walls originating during secondary partitioning of sieve element precursors. The numerous lateral sieve areas intergrade with those of the sieve plates. The pores develop from plasmodesmatal connections and may involve the formation of median cavities. The connections between sieve elements alld companion cells consist of the usual combination of a pore embedded in callose and one plasmodesma or several branches of one on the companion cell side.

Occurrence of Sieve Elements in Phloem Rays

IAWA Journal ◽  
1997 ◽  
Vol 18 (2) ◽  
pp. 197-201 ◽  
Author(s):  
Kishore S. Rajput ◽  
K. S. Rao
Keyword(s):  
Azadirachta Indica ◽  
Tectona Grandis ◽  
Sieve Tube ◽  
Companion Cell ◽  
Secondary Phloem ◽  
Detailed Structure ◽  
Sieve Elements ◽  
P Protein ◽  
Or Groups ◽  
Sieve Plates

Solitary sieve elements or groups of sieve elements were encountered in the rays of secondary phloem of Erythrina indica, Guazuma tomentosa, Acacia nilotica, Azadirachta indica, and Tectona grandis trees. These elements were short and possessed simple and compound sieve plates on their transverse to slightly oblique end walls. Each sieve tube element was associated with a single companion cell at their comers. Like axial sieve tube elements, the sieve tube elements of the rays showed slime (P-protein) plugs and cytoplasmic strands when functional and massive deposition of callose on sieve plates in nonfunctional sieve tube elements. The distribution pattern of these ray sieve elements differed among the species studied. The detailed structure and possible significance of these elements are discussed.

Ultrastructural Aspects of Primary Phloem. Sieve Elements in Poinsettia (Euphorbia Pulcherrima. Euphorbiaceae)

IAWA Journal ◽  
1988 ◽  
Vol 9 (4) ◽  
pp. 363-373 ◽  
Author(s):  
Jennifer Thorsch ◽  
Katherine Esau
Keyword(s):  
Endoplasmic Reticulum ◽  
Leaf Blade ◽  
Protein Body ◽  
Developmental Changes ◽  
Euphorbia Pulcherrima ◽  
Companion Cell ◽  
Sieve Elements ◽  
P Protein ◽  
Companion Cells ◽  
Sieve Plates

Certain developmental changes of sieve elements in the primary phloem of Euphorbia pulcherrima Willd. ex Klotsch (Poinsettia) were examined in the leaf blade, petiole and young stem. The sieve elements have simple sieve plates and, as seen in transection, each is associated with a single companion cell . Since, as expected, our fixed material showed a deposition of callose in sieve plates and in the sieve areas joining the sieve elements with the companion cells, the course of development and distribution of this callose was recorded. The sieve elements contain two types of proteinaceous inclusions, both cytoplasmic in origin. One is the typical form of P-protein composed initially of tubular units; later, the tubules become striated fibrils by stretching. The second inclusion is a nondispersing protein body, the first distinct feature identifying the differentiating sieve elements as such. It persists during the differentiation of the cell and is present in mature sieve elements. Aggregated endoplasmic reticulum is rather sparse in sieve elements, but the typical stacked form is occasionally observed in mature cells.

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