Sieve tube elements in the stem of Neptunia oleracea Lour

1968 ◽  
Vol 16 (3) ◽  
pp. 433 ◽  
Author(s):  
JJ Shah ◽  
MR James
Keyword(s):  
Aquatic Plant ◽  
Sieve Tube ◽  
Sieve Plate ◽  
Callose Deposition ◽  
Nuclear Disintegration ◽  
Full Development ◽  
Companion Cells ◽  
Sieve Plates ◽  
Structural Aspects ◽  
Sieve Tube Element

Some structural aspects of the phloem of Neptunia oleracea, an aquatic plant, are reported. The sieve tube elements on an average are 190μ long and 13μ wide and have compound sieve plates at varying degrees of inclination. The developing sieve tube element has a single large spindle-shaped slime body, which presumably has an outer membrane. The slime body undergoes dispersal before or after full development of the sieve plate, but often nuclear degeneration occurs first. Distinct slime plugs are absent. Plastids and other granular bodies are attached to many of the strands, which are less than 0.5μ in diameter. During the process of nuclear disintegration the nuclear membrane is indistinct, and extruded nucleolus is not observed. Sieve areas and connections are comparatively few in number, and the sieve areas and wall connections as well as the sieve plates show scanty callose deposition. Plastids are abundant in the sieve tube elements, especially near the sieve plates. The companion cells of two consecutive sieve tube elements are placed on alternate sides and hence their longitudinal continuity is not always maintained. Companion cells do not exceed the length of the sieve tube element.

Histology and ultrastructure of oat blue dwarf virus infected oats

1972 ◽  
Vol 50 (12) ◽  
pp. 2511-2520 ◽  
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.

scholarly journals Sieve tube structural variation in Austrobaileya scandens and its significance for lianescence

2021 ◽  
Author(s):  
Juan M Losada ◽  
Zhe He ◽  
Noel Michele Holbrook
Keyword(s):  
Structural Variation ◽  
Vascular System ◽  
Light And Electron Microscopy ◽  
Sieve Tube ◽  
Phloem Transport ◽  
Sieve Plate ◽  
Geometrical Properties ◽  
Mechanical Constraints ◽  
Vascular Elements ◽  
Sieve Plates

Lianas are characterized by large leaf areas and slender stems, a combination of features that require an efficient vascular system. The only extant member of the Austrobaileyaceae, is an endemic twining liana of the tropical Australian forests with well-known xylem hydraulic traits. However, the vascular phloem continuum through aerial organs remains understudied. We analyzed the structure of phloem conduits across leaf veins and stems of A. scandens, combining topological data obtained through light and electron microscopy, with current models of phloem transport. Leaves displayed a low xylem to phloem ratio compared with leaves of other angiosperms, with vascular elements invariant in diameter along the midrib, but tapered across vein hierarchies. Sieve plate pore radii were extremely small: 0.08μm in minor veins, increasing to 0.12μm in the petiole and only to 0.20μm at the base of the stem, tens of meters away. Searcher branches contained tube shaped phloem conduits with a pectin-rich wall, whereas twining stems displayed sieve elements with tangential connections that displayed a greater fraction of the tubes populated with an astonishing number of sieve plates. Hydraulic segmentation of the leaves in Austrobaileyaceae correlate with vesseless leaves that benefit photoassimilate export through volumetric scaling of the sieve tube elements. Yet, compared with canopy dominant trees, the geometrical properties of the sieve tube in twining stems, restrict considerably energy distribution in the sub-canopy layers, potentially favoring the allocation of assimilates toward the elongating branches. Thus, the conductive xylem of twining stems contrasts with a poorly conductive phloem that meets the mechanical constraints of lianescence.

scholarly journals Phytoplasma-Triggered Ca2+ Influx Is Involved in Sieve-Tube Blockage

2013 ◽  
Vol 26 (4) ◽  
pp. 379-386 ◽  
Author(s):  
Rita Musetti ◽  
Stefanie V. Buxa ◽  
Federica De Marco ◽  
Alberto Loschi ◽  
Rachele Polizzotto ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Host Plants ◽  
Sieve Tube ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Wall Thickening ◽  
Sieve Plate ◽  
Callose Deposition ◽  
Phytoplasma Infection ◽  
Sieve Tubes

Phytoplasmas are obligate, phloem-restricted phytopathogens that are disseminated by phloem-sap-sucking insects. Phytoplasma infection severely impairs assimilate translocation in host plants and might be responsible for massive changes in phloem physiology. Methods to study phytoplasma- induced changes thus far provoked massive, native occlusion artifacts in sieve tubes. Hence, phytoplasma-phloem relationships were investigated here in intact Vicia faba host plants using a set of vital fluorescent probes and confocal laser-scanning microscopy. We focused on the effects of phytoplasma infection on phloem mass-flow performance and evaluated whether phytoplasmas induce sieve-plate occlusion. Apparently, phytoplasma infection brings about Ca2+ influx into sieve tubes, leading to sieve-plate occlusion by callose deposition or protein plugging. In addition, Ca2+ influx may confer cell wall thickening of conducting elements. In conclusion, phytoplasma effectors may cause gating of sieve-element Ca2+ channels leading to sieve-tube occlusion with presumptive dramatic effects on phytoplasma spread and photoassimilate distribution.

Studies on the Phloem Sealing Mechanism in Ricinus Fruit Stalks

1983 ◽  
Vol 10 (6) ◽  
pp. 561 ◽  
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.

Anatomical effects of 2,4-DB on tomato internodes

1981 ◽  
Vol 59 (9) ◽  
pp. 1749-1760
Author(s):  
Thompson Demetrio Pizzolato ◽  
David L. Regehr
Keyword(s):  
Secondary Wall ◽  
Sieve Tube ◽  
Tracheary Elements ◽  
Anatomical Changes ◽  
Companion Cells ◽  
Sieve Tubes ◽  
Secondary Wall Formation ◽  
Sieve Plates ◽  
Internal Phloem ◽  
Stimulation Of

Anatomical changes induced in the first internode by an aqueous spray of 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB) (0.56 kg acid equivalent per hectare) confirmed the intolerance of tomato to this herbicide. Hypertrophy, hyperplasia, and plastid destruction occurred rapidly in most tissues. Many of the hyperplastic phloem cells differentiated into unusual supernumerary sieve tube members which were shorter and narrower than normal and which approximated the size of the co-differentiating companion cells. The supernumerary sieve tube members usually possessed several sieve plates and formed sieve tubes which did not follow a vertical course. Although obliteration of the supernumerary sieve tube members was stimulated, it was not associated with the formation of necrotic masses. Secondary wall formation was prevented in the protophloem fibers which became multiseptate following the stimulation of mitoses. The cambial initials were converted into a tissue of squat cells with little organization. Xylem which differentiated after treatment lost its normal heterogeneity and became a tissue of squat tracheary elements and parenchyma with scanty secondary thickening resembling wound xylem. Included phloem differentiated from parenchymatous masses within the xylem, and tylosis formation was stimulated. Pith volume increased by hypertrophy unaccompanied by hyperplasia. Although protophloem fibers did not mature in the internal phloem and limited hyperplasia and hypertrophy did occur, the internal phloem was much less affected than the external. Similarities between the anatomical effects of 2,4-DB and those reported for certain growth regulators and pathogens were noted.

scholarly journals Sieve tube structural variation in Austrobaileya scandens and its significance for lianescence

2021 ◽  
Author(s):  
Juan Losada ◽  
Zhe He ◽  
Noel Holbrook
Keyword(s):  
Resource Allocation ◽  
Hydraulic Resistance ◽  
Structural Variation ◽  
Vascular System ◽  
Sieve Tube ◽  
Sink Strength ◽  
Sieve Plate ◽  
Vascular Elements ◽  
Microscopy Analysis ◽  
Sieve Plates

Lianas combine large leaf areas with slender stems, features that require an efficient vascular system. The only extant member of the Austrobaileyaceae is an endemic twining liana of the tropical Australian forests with well-known xylem hydraulics, but the vascular phloem continuum aboveground remains understudied. Microscopy analysis across leaf veins and stems of A. scandens revealed a low foliar xylem to phloem ratio, with isodiametric vascular elements along the midrib, but tapered across vein orders. Small sieve plate pore radii increased from 0.08 µm in minor veins to 0.12 µm in the petiole, but only to 0.20 µm at the stem base, tens of meters away. In searcher branches, phloem conduits contained a pectin-rich wall and simple plates, whereas in twinning stems, conduits connected through highly-angled-densely populated sieve plates. Twisted and elongated stems of A. scandens display a high hydraulic resistance of phloem conduits, which decreases from leaves to stems, efficiently delivering photoassimilate from sources under Münch predictions. Sink strength of a continuously growing canopy might be stronger than in self-supporting understory plants, favoring resource allocation to aerial organs in angiosperms that colonized the vertical niche.

scholarly journals Anatomy of Brazilian Cereeae (subfamily Cactoideae, Cactaceae): Arrojadoa Britton & Rose, Stephanocereus A. Berger and Brasilicereus Backeberg

2007 ◽  
Vol 21 (4) ◽  
pp. 813-822 ◽  
Author(s):  
Patricia Soffiatti ◽  
Veronica Angyalossy
Keyword(s):  
Secondary Xylem ◽  
Sieve Tube ◽  
Vascular Bundles ◽  
Campos Rupestres ◽  
Espinhaço Range ◽  
Diagnostic Characters ◽  
Bordered Pits ◽  
Companion Cells ◽  
Southern Bahia ◽  
Perforation Plates

(Anatomy of Brazilian Cereeae (subfamily Cactoideae, Cactaceae): Arrojadoa Britton & Rose, Stephanocereus A. Berger wâBrasilicereus Backeberg). Arrojadoa, Stephanocereus and Brasilicereus are endemic Brazilian Cereeae, occurring along the Espinhaço Range, in the campos rupestres, cerrados and caatingas, from northern Minas Gerais to southern Bahia. The genera are columnar, erect to semi-erect cacti, except for one species, A bahiensis, which is globose. This study describes the anatomy of dermal, fundamental and vascular systems, aiming to find diagnostic characters for the genera and species. Basal portions of stems were sectioned transversely and longitudinally, and stained with Astrablue and Safranin. The species share a uniseriate epidermis, with thick cuticle; well developed collenchymatic hypodermis, containing prismatic crystals; cortex with numerous mucilage cells, druses and vascular bundles; outside cortex as a palisade parenchyma; periderm composed of lignified cork cells alternating with suberized cells; pheloderm consisting of a few layers of thin-walled cells; phloem composed of solitary or multiple of two to three sieve tube elements, companion cells, axial and radial parenchyma; secondary xylem with solitary to multiple vessels, with simple perforation plates and alternate bordered to semi-bordered pits; axial parenchyma scanty vasicentric to incomplete; libriform septate fibres; large rays. Unlignified parenchyma is seen in the secondary xylem, varying from a few cells to bands among axial and radial elements. The following are considered diagnostic characters: the shape of lignified phellem cells, cubic to radially elongate, which individualizes S. leucostele; an underdeveloped hypodermis and the occurrence of sclereids in the cortex are exclusive to Brasilicereus markgrqfii.

scholarly journals THE FINE STRUCTURE AND DEVELOPMENT OF THE COMPANION CELL OF THE PHLOEM OF ACER PSEUDOPLATANUS

1965 ◽  
Vol 24 (1) ◽  
pp. 117-128 ◽  
Author(s):  
F. B. P. Wooding ◽  
D. H. Northcote
Keyword(s):  
Endoplasmic Reticulum ◽  
Sieve Tube ◽  
Acer Pseudoplatanus ◽  
Sieve Plate ◽  
Wheat Grain ◽  
Companion Cell ◽  
Large Nucleus ◽  
Cell Organelles ◽  
Phloem Tissue ◽  
Aleurone Cells

At maturity the companion cell of the phloem of the sycamore Acer pseudoplatanus has a large nucleus, simple plastids closely sheathed with rough endoplasmic reticulum, and numerous mitochondria. The cytoplasm contains numerous ribosomes, resulting in a very electron-opaque cytoplasm after permanganate fixation. Bodies similar to the spherosomes of Frey-Wyssling et al. (4) are collected in clusters and these also contain bodies of an unidentified nature similar to those found by Buttrose (1) in the aleurone cells of the wheat grain. The pores through the wall between the companion cell and sieve tube are complex and develop from a single plasmodesma. Eight to fifteen plasmodesmata on the companion cell side communicate individually with a cavity in the centre of the wall which is linked to the sieve tube by a single pore about twice the diameter of an individual plasmodesma. This pore is lined with material of an electron opacity equivalent to that of material bounding the sieve plate pores. The development of the cell organelles, the possible role played in the phloem tissue by the companion cell, and the function of the complex pores contained in its wall are 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.

SECONDARY GROWTH IN THE STEM OF SOME SPECIES OF ALTERNANTHERA AND ACHYRANTHES ASPERA (AMARANTHACEAE)

IAWA Journal ◽  
2000 ◽  
Vol 21 (4) ◽  
pp. 417-424 ◽  
Author(s):  
Kishore S. Rajput ◽  
K.S. Rao
Keyword(s):  
Secondary Growth ◽  
Sieve Tube ◽  
Axial Parenchyma ◽  
Achyranthes Aspera ◽  
Companion Cells ◽  
Cambial Variant ◽  
Mother Cells

Secondary growth in Achyranthes aspera, Alternanthera polygamous, A. pungens, A. sessilis, and A. triandra was achieved by the development of a cambial variant resulting in successive rings of xylem and phloem. Each new cambium was developed at a distance about two to three cells external to the phloem produced by the previous cambium. The development of phloem was not synchronous in the species studied. Phloem development started either simultaneously with xylem or after the formation of a few xylem derivatives. In Achyranthes, xylem production started first followed by the development of phloem. Phloem mother cells differentiated into sieve tube elements, companion cells and axial parenchyma. Xylem was storied and exclusively composed of axial elements. Radial elements were absent in all the xylem rings of the stem. Vessels were angular and mostly solitary, but radial and tangential multiples were also observed occasionally. Xylem fibres were nonseptate and nucleated. Development of phloem and the rayless nature of the xylem is discussed.

Sign in / Sign up

Export Citation Format

Share Document