RELATION OF BEET YELLOWS VIRUS TO THE PHLOEM AND TO MOVEMENT IN THE SIEVE TUBE

In minor veins of leaves of Beta vulgaris L. (sugar beet) yellows virus particles were found both in parenchyma cells and in mature sieve elements. In parenchyma cells the particles were usually confined to the cytoplasm, that is, they were absent from the vacuoles. In the sieve elements, which at maturity have no vacuoles, the particles were scattered throughout the cell. In dense aggregations the particles tended to assume an orderly arrangement in both parenchyma cells and sieve elements. Most of the sieve elements containing virus particles had mitochondria, plastids, endoplasmic reticulum, and plasma membrane normal for mature sieve elements. Some sieve elements, however, showed evidence of degeneration. Virus particles were present also in the pores of the sieve plates, the plasmodesmata connecting the sieve elements with parenchyma cells, and the plasmodesmata between parenchyma cells. The distribution of the virus particles in the phloem of Beta is compatible with the concept that plant viruses move through the phloem in the sieve tubes and that this movement is a passive transport by mass flow. The observations also indicate that the beet yellows virus moves from cell to cell and in the sieve tube in the form of complete particles, and that this movement may occur through sieve-plate pores in the sieve tube and through plasmodesmata elsewhere.

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

Acta Societatis Botanicorum Poloniae ◽

10.5586/asbp.2001.022 ◽

2014 ◽

Vol 70 (3) ◽

pp. 173-180 ◽

Cited By ~ 4

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 Limonium sinuatum 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 L. sinuatum 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.

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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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Seasonal Changes in Callose Levels and Fluorescein Translocation in the Phloem of Vitis Vinifera L.

IAWA Journal ◽

10.1163/22941932-90001247 ◽

1991 ◽

Vol 12 (3) ◽

pp. 223-234 ◽

Cited By ~ 13

Author(s):

Roni Aloni ◽

Carol A. Peterson

Keyword(s):

Vitis Vinifera ◽

Sieve Tube ◽

Growing Season ◽

Early Spring ◽

Vitis Vinifera L ◽

First Year ◽

Secondary Phloem ◽

Radial Gradient ◽

Sieve Tubes ◽

Sieve Plates

The secondary phloem of Vitis vinifera L. is characterised by a radial gradient of sieve tube diameters. Sieve tubes maturing early in the growing season have the largest diameters; those maturing late in the season have the smallest. In early spring, masses of winter dormancy callose are gradually digested in a polar radial pattern, proceeding outwards from the cambium. The fluorescent dye, fluorescein, was used to detect translocation in sieve tubes. During spring, dye translocation was first observed in the wider sieve tubes produced near the end of the previous year and wh ich had reduced amounts of callose. But translocation was not observed in the very narrow sieve tubes formed at the end of the year although they were the first to be callose free. The reactivated sieve tubes functioned for about one month. New sieve tubes differentiated three weeks after dormancy callose breakdown and started to function about one week later, so that the transition of translocation activity from the sieve tubes of the previous year to those of the current year is relatively rapid. The sieve tubes formed toward the end of the growing season (but not the narrowest ones formed at the very end of the season) function during parts of two successive seasons, while the sieve tubes forrned early in the season usually function during the first year only. Callose amounts increase gradually during summer in both the old and new sieve tubes and become relatively heavy in the old ones. At this developmental stage, translocation occurs through young sieve plates with relatively high callose deposits.

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Leaf structure of Cananga odorata (Annonaceae) in relation to the collection of photosynthate and phloem loading: morphology and anatomy

Canadian Journal of Botany ◽

10.1139/b90-047 ◽

1990 ◽

Vol 68 (2) ◽

pp. 354-363 ◽

Cited By ~ 10

Author(s):

David G. Fisher

Keyword(s):

Sieve Tube ◽

Type I ◽

Type Ii ◽

Tracheary Elements ◽

Minor Vein ◽

Type Iv ◽

Parenchyma Cells ◽

Vascular Parenchyma ◽

Sieve Tubes ◽

Cananga Odorata

Four distinct anatomical types of minor veins occur in Cananga odorata leaves. In order of decreasing size, they are (i) type I, with tracheary elements, fibers, vascular parenchyma cells, companion cells, and mostly nacreous-walled sieve-tube members; (ii) type II, with the same cell types except that the sieve-tube members have walls that usually lack nacreous thickenings; (iii) type III, with only vascular parenchyma cells and tracheids; and (iv) type IV (vein endings), with tracheary elements only. The proportions of the total minor vein length occupied by each are type I, 15.1%; type II, 27.2%; type III, 24.4%; and type IV, 33.3%. Thus about 60% of the minor vein network lacks sieve tubes. The average interveinal distance for all minor veins is 121 μm, but the average for veins containing sieve-tubes is 329 μm. Other salient features include vascular parenchyma cells up to 130 μm long, bundle-sheath cells whose lateral protuberances into the mesophyll increase extensively with decreasing vein size, and five layers of horizontally oriented spongy parenchyma cells. These features may facilitate transport of assimilate to the relatively small proportion of the minor vein network that contains sieve tubes.

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Sieve Plate Pores in the Phloem and the Unknowns of Their Formation

Plants ◽

10.3390/plants8020025 ◽

2019 ◽

Vol 8 (2) ◽

pp. 25 ◽

Cited By ~ 5

Author(s):

Lothar Kalmbach ◽

Ykä Helariutta

Keyword(s):

Pore Formation ◽

Current Knowledge ◽

Sieve Tube ◽

Model Species ◽

Sieve Elements ◽

Plasmodesmata Formation ◽

Sieve Tubes ◽

Element Evolution ◽

Electron Microscopes ◽

Sieve Pores

Sieve pores of the sieve plates connect neighboring sieve elements to form the conducting sieve tubes of the phloem. Sieve pores are critical for phloem function. From the 1950s onwards, when electron microscopes became increasingly available, the study of their formation had been a pillar of phloem research. More recent work on sieve elements instead has largely focused on sieve tube hydraulics, phylogeny, and eco-physiology. Additionally, advanced molecular and genetic tools available for the model species Arabidopsis thaliana helped decipher several key regulatory mechanisms of early phloem development. Yet, the downstream differentiation processes which form the conductive sieve tube are still largely unknown, and our understanding of sieve pore formation has only moderately progressed. Here, we summarize our current knowledge on sieve pore formation and present relevant recent advances in related fields such as sieve element evolution, physiology, and plasmodesmata formation.

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Histology and ultrastructure of oat blue dwarf virus infected oats

Canadian Journal of Botany ◽

10.1139/b72-322 ◽

1972 ◽

Vol 50 (12) ◽

pp. 2511-2520 ◽

Cited By ~ 18

Author(s):

R. J. Zeyen ◽

E. E. Banttari

Keyword(s):

Light Microscopy ◽

Sieve Tube ◽

Dwarf Virus ◽

Electron Microscopic ◽

Virus Particles ◽

Procambial Strand ◽

Sieve Plates ◽

Aster Leafhopper ◽

Sieve Tube Element

The oat blue dwarf virus is a small spherical virus (28–30 nm) in diameter and is obligatorily transmitted by the aster leafhopper Macrosteles fascifrons Stål. The virus causes abnormalities in the phloem development of infected plants. Hyperplasia and limited hypertrophy of phloic procambium, in a given procambial strand, begin only after the maturation of the first protophloem sieve-tube element in that particular localized area. The majority of phloem elements produced in hyperplastic areas are parenchymatous, have truncated end walls, and lack sieve plates. Electron-microscopic observations substantiated the hypothesis that the virus was phloem-limited by revealing virus particles only in phloem elements. The greatest accumulation of virus particles was observed in the region between immature and fully vacuolated phloem elements, implicating virus synthesis in immature elements. Crystals of virus particles were often large enough to be seen by light microscopy.

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The occurrence and development of intraxylary phloem in young Aquilaria sinensis shoots

IAWA Journal ◽

10.1163/22941932-40190221 ◽

2019 ◽

Vol 40 (1) ◽

pp. 23-42

Author(s):

Bei Luo ◽

Tomoya Imai ◽

Junji Sugiyama ◽

Jian Qiu

Keyword(s):

Growth Period ◽

Maturation Stage ◽

Aquilaria Sinensis ◽

Callose Deposition ◽

Active Growth ◽

Primary Xylem ◽

Parenchyma Cells ◽

Interxylary Phloem ◽

Sieve Tubes ◽

Sieve Plates

ABSTRACT Agarwoods such as Aquilaria spp. and Gyrinops spp. (Thymelaeaceae) produce interxylary phloem in their secondary xylem and intraxylary phloem at the periphery of the pith, facing the primary xylem. We studied young shoots of Aquilaria sinensis and characterized the development of its intraxylary phloem. It was initiated by the division of parenchyma cells localized in the outer parts of the ground meristem immediately following the maturation of first-formed primary xylem. Its nascent sieve plates bore donut-like structures, the individual pores of which were so small (less than 0.1 μm) that they were hardly visible under FE-SEM. Intraxylary phloem developed into mature tissue by means of the division and proliferation of parenchyma cells. During the shoots’ active growth period, the sieve pore sizes were 0.1–0.5 μm, with tubular elements passing through them. In the maturation stage, large clusters of sieve tubes continued to be differentiated in the intraxylary phloem. In the partial senescence stage observed in a three-centimeter-diameter branch, intraxylary phloem cells in the adaxial part became crushed, and sieve plates had pores over 1–2 μm in diameter without any callose deposition. Before and after the differentiation of interxylary phloem in the first and second internodes, callose staining detected more than twice as many sieve tubes in intraxylary phloem than in external phloem. However, after differentiation of interxylary phloem in the eleventh internode, more sieve tubes were found in interxylary phloem than in intraxylary and external phloem. This suggests that prior to the initiation of interxylary phloem intraxylary phloem acts as the principal phloem. After its differentiation, however, interxylary phloem takes over the role of principal phloem. Interxylary phloem thus acts as the predominant phloem in the translocation of photosynthates in Aquilaria sinensis.

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Changes of ultrastructure and cytoplasmic free calcium in Gladiolus x hybridus Van Houtte roots infected by aster yellows phytoplasma

Acta Societatis Botanicorum Poloniae ◽

10.5586/asbp.2003.035 ◽

2011 ◽

Vol 72 (4) ◽

pp. 269-282 ◽

Cited By ~ 9

Author(s):

Anna Rudzińska-Langwald ◽

Maria Kamińska

Keyword(s):

Calcium Ions ◽

Infected Plant ◽

Sieve Tube ◽

Plant Roots ◽

Free Calcium ◽

Aster Yellows ◽

Companion Cells ◽

Parenchyma Cells ◽

Sieve Tubes ◽

Aster Yellows Phytoplasma

Roots of Gladiolus x hybridus Van Houtte plants infected with aster yellows phytoplasma were examined. The infected plants had a reduced root system in comparison to control plants. Their roots were thinner and the stele organisation was changed. Phytoplasmas were present in sieve tubes, companion cells and phloem parenchyma cells of the infected plant roots. Free calcium ions were localized in the cells of infected plants. Cells of the stele of infected roots, especially these infected with phytoplasmas, showed an increase of calcium antimonite deposits in theirs protoplasts. Also the number of calcium antimonite deposits increased in sieve tubes of infected roots. The deposits were present on plasma membrane, around the sieve tube plate and also in the lumen of the sieve tube. The increase of free calcium ions in sieve tubes did not cause the occlusion of sieve tube pores. Companion cells and some parenchyma cells with phytoplasmas did not react to phytoplasma infection with an increase of Ca2+ ions in protoplast. The parenchyma cells showing signs of degeneration reacted with high increase of calcium ions. The Ca2+ ions were present mainly in cytoplasm of infected parenchyma cells. There were calcium antimonite deposits in infected plant roots xylem elements and in intracellular spaces of cortex parenchyma. Such deposits were not present in control plants.

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Studies on the Phloem Sealing Mechanism in Ricinus Fruit Stalks

Functional Plant Biology ◽

10.1071/pp9830561 ◽

1983 ◽

Vol 10 (6) ◽

pp. 561 ◽

Cited By ~ 3

Author(s):

J Kallarackal ◽

JA Milburn

Keyword(s):

Electron Microscopy ◽

Sieve Tube ◽

Sieve Plate ◽

Tube System ◽

Phloem Sap ◽

Starch Grains ◽

P Protein ◽

Sieve Tubes ◽

Sealing Mechanism ◽

Sieve Plates

Fruit stalks of R. communis were made to exude phloem sap by repeated slicing at intervals of a few minutes. Samples 1 mm thick from the fruit stalks were fixed for electron microscopy. Samples were also fixed and processed for electron microscopy from previously intact (non-exuding) fruit stalks. Examination of the sieve tubes from these two different samples showed predominantly open sieve-plate pores in the exuding fruit stalk. The sieve plates of the non-exuding fruit stalk showed occlusion of the sieve-plate pores by P-protein. The starch grains from the broken plastids also had characteristic distributions. The implications of these observations are discussed in relation to comprehending the mechanism by which sieve-plate pores become choked, and so sealing the sieve-tube system as a result of injury.

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Comparative Anatomy of the Secondary Phloem of Ten Species of Rosaceae

IAWA Journal ◽

10.1163/22941932-90001332 ◽

1993 ◽

Vol 14 (3) ◽

pp. 289-298 ◽

Cited By ~ 4

Author(s):

Liu Donghua ◽

Gao Xinzeng

Keyword(s):

Comparative Anatomy ◽

Secondary Phloem ◽

Sieve Elements ◽

Companion Cells ◽

Parenchyma Cells ◽

Sieve Plates ◽

Lateral Walls

The anatomy of the secondary phloem of species belonging to four genera in Rosaceae is described. The three genera of the Maloideae studied are more or less similar in their phloem anatomy; tangential bands of fibresclereids alternate with bands of sieve elements, companion cells and parenchyma cells; superficially, the nonconducting and conducting phloem are not distinct from one another; sieve plates are compound and there are conspicuous sieve areas on lateral walls; rays are uniseriate and multiseriate, and homocellular. In the five species of Prunus (Prunoideae) studied, there are no fibre-sclereids in the conducting phloem, end walls bearing simple sieve plates are oblique to nearly horizontal; and rays are uniseriate and multiseriate, homocellular.

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