Electrophysiological approach to determine kinetic parameters of sucrose uptake by single sieve elements or phloem parenchyma cells in intact Vicia faba plants

The vascular anatomy and phloem ultrastructure of the sugar beet petiole were studied in an attempt to evaluate the potential of petiolar phloem anastomoses to accommodate lateral movement of translocates across this structure. Clearings revealed that six of the eight interveinal regions between the nine major, axially oriented veins were connected by many anastomoses. The two interveinal areas characterized by the fewest anastomoses were located near the margin of the petiole. It was concluded that lateral translocation via anastomoses would be most efficient in the central part of the petiole. A light microscope study of the structure of the junction between anastomosing and continuous veins revealed that the sieve elements of each of the merging veins were separated from each other, for distances of up to 6 mm beyond the point of initial contact, by phloem parenchyma cells. The presence of phloem parenchyma cells in this position, and between the clusters of sieve elements that occur across the phloem of the large bundles, was taken as an indication that the parenchyma cells may have an important role in lateral translocation. An ultrastructural study of the petiolar phloem revealed that the phloem parenchyma and companion cells could be easily distinguished on the basis of the structure of the chloroplasts, dictyosomes, and endoplasmic reticulum. Microfilament bundles and spine-coated tubules and (or) vesicles were uniquely present in the parenchyma cells. The ultrastructure of the phloem parenchyma cells is discussed relative to their possible role in mediating the movement of sugars through the anastomoses.

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Effects of Root Restriction on Ultrastructure of Phloem Tissues in Grape Berry

HortScience ◽

10.21273/hortsci.44.5.1334 ◽

2009 ◽

Vol 44 (5) ◽

pp. 1334-1339 ◽

Cited By ~ 6

Author(s):

ZhaoSen Xie ◽

Charles F. Forney ◽

WenPing Xu ◽

ShiPing Wang

Keyword(s):

Growth Phase ◽

Rapid Growth ◽

Developmental Process ◽

Grape Berry ◽

Control Treatment ◽

Sieve Elements ◽

Phloem Parenchyma ◽

Parenchyma Cells ◽

Variation Explained ◽

Root Restriction

In this study, the ultrastructure of phloem and its surrounding parenchyma cells in the developing grape berry produced under root restriction or without (control) was for the first time systematically investigated through transmission electron microscopy during the entire developmental process of the berry. The results showed that root restriction increased the number of plasmodesmata between sieve elements (SE) and companion cells (CC) and between the SE/CC complex and phloem parenchyma cells. Sieve elements in fruit produced under root restriction were smaller in size than those from the control treatment, but CC were bigger than in the control treatment. During the first rapid growth phase of the grape berry, there was denser cytoplasm in the CC produced under root restriction having more abundant mitochondria, endoplasmic reticulum, multivesicular bodies, vesicles, and plastids than in control fruit. During the second rapid growth phase of the grape berry, CC under root restriction showed more serious plasmolysis. Cytoplasmic contents such as vesicles were fused into the vacuole of which the tonoplast nearly disappeared in the phloem parenchyma cells, and cytoplasmic contents in fruit cells produced under root restriction became denser than the control treatment. These results demonstrated that grape berry adapted to the root restriction stress through ultrastructure variation of the phloem, and this variation explained the increase of photosynthate accumulation in the grape berry observed under root restriction.

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Inclusions in nuclei and plastids of Boraginaceae and their possible taxonomic significance

Canadian Journal of Botany ◽

10.1139/b89-442 ◽

1989 ◽

Vol 67 (12) ◽

pp. 3608-3617 ◽

Cited By ~ 4

Author(s):

Deborah D. Fisher ◽

Jennifer Thorsch ◽

Katherine Esau

Keyword(s):

Proteolytic Enzyme ◽

Ultrastructural Level ◽

Sieve Element ◽

Nuclear Inclusions ◽

Sieve Elements ◽

Phloem Parenchyma ◽

The Family ◽

Parenchyma Cells ◽

Parallel Arrangement ◽

Systematic Character

A survey of 68 species representing 28 genera in the family Boraginaceae was conducted at the ultrastructural level to determine presence of nuclear crystalloids in sieve elements and occurrence of crystalline structures in chloroplasts of phloem parenchyma cells. Nuclear crystalloids were identified in 55 of the species examined, and 25 of the species contained chloroplast crystals. The nuclear crystals were mainly composed of thin rods densely packed in parallel arrangement. Their sizes, shapes, and numbers varied, but they were basically prismatic or possibly cubical. During maturation, the sieve element nuclei disintegrated and the crystalloids were released into the cell lumen where they remained intact. Loosely arranged paracrystalline components associated with the dense nuclear crystalloids were found only in the genus Amsinckia. Crystalline inclusions in the parenchyma chloroplasts were made up of fibers loosely aligned in a herringbone pattern. The lability of the chloroplast crystals to the proteolytic enzyme, protease, was tested on 10 species, and only Onosma stellulatum Waldst. & Kit. chloroplast crystals were routinely digested. The high percentage of nuclear crystalloids found in this family suggests that these inclusions could be valuable as a systematic character. Key words: sieve elements, nuclear inclusions, plastid crystals, Boraginaceae.

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Fine structure of the phloem of Pisum sativum. II. The companion cell and phloem parenchyma

Australian Journal of Botany ◽

10.1071/bt9650185 ◽

1965 ◽

Vol 13 (2) ◽

pp. 185

Author(s):

MC Wark

Keyword(s):

Fine Structure ◽

Sieve Element ◽

Companion Cell ◽

Secondary Phloem ◽

Sieve Elements ◽

Phloem Parenchyma ◽

Wall Structures ◽

Companion Cells ◽

Parenchyma Cells ◽

Vacuolated Cells

The companion cells of the secondary phloem of Pisum contain all the organelles characteristic of cells possessing an active metabolism. The cytoplasm of the companion cells shows little change during ontogeny. Complex plasmodesmata connect the sieve elements and companion cells. These are the only connections observed between the sieve elements and other phloem cells. New wall structures of the companion cells are described. These structures are here tentatively called trabeculae; they intrude into the cytoplasm, but never completely cross the cell. The trabeculae alter in appearance at the time when the sieve element nucleus and tonoplast disappear. The phloem parenchyma cells are large vacuolated cells wider in diameter but shorter in length than the sieve elements. They contain all the organelles found in normal photosynthetic tissue. The cytoplasm of the phloem parenchyma shows little change during ontogeny. Plasmodesmata of well-developed pit fields connect the phloem parenchyma with the companion cells. The phloem parenchyma does not communicate with the sieve elements.

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Plastids and mitochondria in the phloem of Cucurbita

Canadian Journal of Botany ◽

10.1139/b68-116 ◽

1968 ◽

Vol 46 (7) ◽

pp. 877-880 ◽

Cited By ~ 24

Author(s):

Katherine Esau ◽

James Cronshaw

Keyword(s):

Cell Maturation ◽

Cucurbita Maxima ◽

Starch Grains ◽

Sieve Elements ◽

Phloem Parenchyma ◽

Companion Cells ◽

Structural Abnormalities ◽

Parenchyma Cells ◽

The Matrix

Contrary to some statements in the literature, the sieve elements of Cucurbita maxima Duchesne contain plastids. In young cells these organelles resemble mitochondria with regard to size and density of the matrix; but they have fewer internal membranes. During cell maturation, the plastids enlarge and their contents become thin and electron-transparent. They assume a partly degenerated appearance and do not deposit starch. The plastids of the companion cells resemble those of the young sieve elements but develop a considerable number of internal membranes, which may be organized into typical chloroplast grana. Starch is rarely encountered in these plastids. The plastids of the phloem-parenchyma cells are chloroplasts, commonly including starch grains. The mitochondria are similar in the three categories of cell but those of the sieve elements may show a denser matrix in young cells and structural abnormalities in mature cells.

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Elemental Analysis of Phloem Tissue in Lemna Minor Root Tips

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s1431927600003470 ◽

1980 ◽

Vol 38 ◽

pp. 798-799

Author(s):

Patrick Echlin ◽

Thomas Hayes ◽

Clifford Lai ◽

Greg Hook

Keyword(s):

Vascular Tissue ◽

Lemna Minor ◽

Atomic Weight ◽

Companion Cell ◽

Root Tips ◽

Phloem Tissue ◽

Cell Stage ◽

Phloem Parenchyma ◽

Parenchyma Cells ◽

Xylem Element

Studies (1—4) have shown that it is possible to distinguish different stages of phloem tissue differentiation in the developing roots of Lemna minor by examination in the transmission, scanning, and optical microscopes. A disorganized meristem, immediately behind the root-cap, gives rise to the vascular tissue, which consists of single central xylem element surrounded by a ring of phloem parenchyma cells. This ring of cells is first seen at the 4-5 cell stage, but increases to as many as 11 cells by repeated radial anticlinal divisions. At some point, usually at or shortly after the 8 cell stage, two phloem parenchyma cells located opposite each other on the ring of cells, undergo an unsynchronized, periclinal division to give rise to the sieve element and companion cell. Because of the limited number of cells involved, this developmental sequence offers a relatively simple system in which some of the factors underlying cell division and differentiation may be investigated, including the distribution of diffusible low atomic weight elements within individual cells of the phloem tissue.

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Seasonal changes in the physical nature of the bark phloem parenchyma cells ofPinus strobus

PROTOPLASMA ◽

10.1007/bf02665908 ◽

1960 ◽

Vol 52 (2) ◽

pp. 223-229 ◽

Cited By ~ 11

Author(s):

Johnson Parker

Keyword(s):

Seasonal Changes ◽

Physical Nature ◽

Phloem Parenchyma ◽

Parenchyma Cells

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The secondary phloem of Austrobaileya scandens

Canadian Journal of Botany ◽

10.1139/b70-050 ◽

1970 ◽

Vol 48 (2) ◽

pp. 341-359 ◽

Cited By ~ 22

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.

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Association of malva vein-clearing virus and rhabdoviruslike particles with mottle and vein clearing of malva plants

Canadian Journal of Botany ◽

10.1139/b86-013 ◽

1986 ◽

Vol 64 (1) ◽

pp. 85-89 ◽

Cited By ~ 2

Author(s):

Maria-Ivone C. Henriques ◽

Fernando S. Henriques

Keyword(s):

Inclusion Bodies ◽

Inner Core ◽

Dense Body ◽

Mesophyll Cells ◽

Cytoplasmic Inclusions ◽

Thin Sections ◽

Phloem Parenchyma ◽

Vein Clearing ◽

Perinuclear Space ◽

Parenchyma Cells

Thin sections of malva (Malva sp.) leaves collected in the field and showing mottle and vein-clearing symptoms were examined by electron microscopy. Cytoplasmic inclusions typical of potyvirus and consisting of pinwheels, laminated aggregates, and scrolls were readily observed. In addition, rhabdoviruslike particles were also seen in the perinuclear space of phloem parenchyma cells and within membranous sacs scattered throughout the cytoplasm of other vascular bundle cells. Occasionally rhabdoparticles could be found embedded in an amorphous electron-dense body located within the cell vacuole. The rhabdovirus particles, approximately 75 × 300 nm, were bound by a membrane with outer projections and had an inner core displaying cross striations. The cytoplasm of infected mesophyll cells had chloroplasts containing large amorphous inclusion bodies and had extensive membranous tubules that were frequently associated with the potyvirus inclusions. These ultrastructural aspects, the size of the particles, and the data on host range indicate that malva plants under study were doubly infected by viruses which were tentatively identified as malva vein-clearing virus and a previously undescribed rhabdovirus.

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