scholarly journals Nodal Endoplasmic Reticulum, a Specialized Form of Endoplasmic Reticulum Found in Gravity-Sensing Root Tip Columella Cells

2001 ◽  
Vol 125 (1) ◽  
pp. 252-265 ◽  
Author(s):  
Hui Qiong Zheng ◽  
L. Andrew Staehelin
Keyword(s):  
Endoplasmic Reticulum ◽  
Root Tip ◽  
Specialized Form ◽  
Columella Cells

Megasporogenesis in a heterosporous fern; features of the organelles in meiotic cells and young megaspores

1981 ◽  
Vol 51 (1) ◽  
pp. 109-119
Author(s):  
P.R. Bell
Keyword(s):  
Endoplasmic Reticulum ◽  
Seed Plants ◽  
Differential Survival ◽  
Specialized Form ◽  
Homosporous Ferns ◽  
Genetically Determined

Megasporogenesis in the heterosporous fern Marsilea (Hydropterideae) shows features intermediate between sporogenesis in homosporous ferns and that in heterosporous seed plants. The plastids in the dyads and young spores were associated with tubules 30–35 nm in diameter, probably a specialized form of endoplasmic reticulum. No consistent differences in size or cytoplasmic components could be found between the megaspores of a tetrad that might account for differential survival. The view that megaspore viability within the tetrad is genetically determined is thereby strengthened.

Observations of the Golgi Apparatus in Pisum Primary Roots

1968 ◽  
Vol 26 ◽  
pp. 14-15
Author(s):  
Gordon C. Spink
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Pisum Sativum ◽  
Golgi Apparatus ◽  
Common Garden ◽  
Root Tip ◽  
Garden Pea ◽  
Wall Area ◽  
Primary Roots ◽  
Columella Cells

It is known that the product of the Golgi apparatus vesicles is deposited at and localized in the cell wall. This is accomplished by the formation of the hypertrophied dictyosomes and the subsequent movement of these vesicles to the plasma membrane (Fig. 1). After fusion with the plasma membrane, the secreted material is released into the cell wall area and, in some plants under appropriate conditions, moves outward through the cell wall and appears as a droplet on the root tip.In primary roots of Pisum sativum, var. Alaska (common garden pea) the Golgi apparatus vesicle product accumulates between the plasma membrane and the cell wall, particularly in those cells at the extreme tip of the root. These cells are formed at the acropetal end of the columella cells.

scholarly journals Vacuolar-Type H+ -ATPases Are Associated with the Endoplasmic Reticulum and Provacuoles of Root Tip Cells

1994 ◽  
Vol 106 (4) ◽  
pp. 1313-1324 ◽  
Author(s):  
E. M. Herman ◽  
X. Li ◽  
R. T. Su ◽  
P. Larsen ◽  
Ht. Hsu ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Root Tip ◽  
Tip Cells ◽  
Root Tip Cells

scholarly journals Polyprenyl phosphate sugars synthesized during slime-polysaccharide production by membranes of the root-cap cells of maize (Zea mays)

1979 ◽  
Vol 178 (3) ◽  
pp. 661-671 ◽  
Author(s):  
J R Green ◽  
D H Northcote
Keyword(s):  
Endoplasmic Reticulum ◽  
Zea Mays ◽  
Neutral Lipids ◽  
Root Tip ◽  
Synthetase Activity ◽  
Root Tips ◽  
Maize Roots ◽  
Glucose Derivatives

Two types of experiments were carried out; either maize roots were incubated in L-[1-3H]fucose or membranes were prepared from root tips and these were incubated with GDP-L-[U-14C]fucose or UDP-D-[U-4C]glucose. The radioactively labelled lipids that were synthesized in vivo and in vitro were extracted and separated into polar and neutral components. The polar lipids had the characteristics of polyprenyl phosphate and diphosphate fucose or glucose derivatives, and the neutral lipids of sterol glycosides (fucose or glucose). A partial separation of the glycolipid synthetase reactions was achieved. Membranes were fractionated into material that sedimented at 20,000g and 100,000g. Most of the polar glycolipid synthetase activity (for the incorporation of both fucose and glucose) was located in the 100,000 g pellet, and this activity was probably located in the endoplasmic reticulum. The neutral lipid, which contained fucose, was synthesized mainly by membranes of the 20,000g pellet, and the activity was probably associated with the dictyosomes, whereas the neutral glucolipids were synthesized by all the membrane fractions. It is suggested that the polar (polyprenyl) lipids labelled with fucose could act as possible intermediates during the synthesis of the glycoproteins and slime in the root tip.

Ontogénie des laticifères du système primaire de l’Hevea brasiliensis: une étude ultrastructurale et cytochimique

1981 ◽  
Vol 59 (6) ◽  
pp. 974-985 ◽  
Author(s):  
Charles Hébant
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Surface Film ◽  
Secretory Cells ◽  
Primary System ◽  
Parenchyma Cells ◽  
Rubber Particles ◽  
Specialized Form ◽  
Hydrolysis Of

The development of the laticifers of the primary system in the roots of young seedlings of Hevea is investigated. The nucleus of the maturing secretory cells progressively diminishes in size, thus giving rise to a dense "pycnotic" body. Plastids of primary laticifers show an organization intermediate between that of plastids of neighbouring parenchyma cells and that of the Frey-Wyssling complexes of the secondary laticifers. The continuity of the vacuome sensu lato is underlined. The lutoids, a specialized form of "polydisperse vacuome," show a relationship with the endoplasmic reticulum; these lutoïds can also incorporate rubber particles. The ontogeny of cell wall perforations is described; a progressive hydrolysis of the wall results in its gradual thinning followed by its disruption. Rubber particles are initiated as discrete inclusions within the protoplasm. A thin surface film is identifiable on them, the staining properties of which change during the maturation of the particles. The protoplasm of adult laticifers is densely packed with rubber particles.

scholarly journals UNE FORME MICROTUBULAIRE ET PARACRISTALLINE DE RETICULUM ENDOPLASMIQUE DANS LES PHOTOCYTES DES ANNELIDES POLYNOINÆ

1966 ◽  
Vol 31 (1) ◽  
pp. 135-158 ◽  
Author(s):  
J. M. Bassot
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Fine Structure ◽  
Nuclear Envelope ◽  
Contact Surface ◽  
Special Kind ◽  
The Other ◽  
Cytoplasmic Organelle ◽  
Specialized Form

Luminous cells of polynoid worm elytra have been examined by methods of electron microscopy, with special attention focused on the fine structure of photogenic grains. These cells send apical prolongations into the mid-part of the elytra. The plasma membrane is very sinuous, and a special kind of desmosome links two portions of the same membrane. In addition to all the organelles which can be found in nonluminescent epithelial cells of the elytra, numerous photogenic grains are contained in their cytoplasm. These grains are composed of undulating microtubules measuring 200 A in diameter; their disposition in the grain is highly regular, and the grains appear as paracrystals. At the borders of the grains, the walls of the microtubules are often in continuity with those of the endoplasmic reticulum and with the external membrane of the nuclear envelope. Because of this fact, the microtubules of the grains may be considered a cytoplasmic organelle, representing a specialized form of the endoplasmic reticulum. The microtubules permit the repartition, inside and outside their walls, of two different products, one being forty-three times more abundant than the other; thus, the contact surface, in comparison to the volume, is greatly increased. The induction of the luminous reaction by change in the permeability of the microtubule walls, allowing contact between the two substances, is suggested as a working hypothesis. There is an evolution of the grains along the axis of the photocytes. The grains are often surrounded by progressively increasing amounts of glycogen. Their paracrystalline disposition is altered at the apex of the luminous cells.

Ultrastructural and developmental alterations induced by Periconia circinata toxin in the root tip of sorghum

1983 ◽  
Vol 61 (5) ◽  
pp. 1491-1505 ◽  
Author(s):  
Jonathan A. Arias ◽  
Larry D. Dunkle ◽  
Charles E. Bracker
Keyword(s):  
Endoplasmic Reticulum ◽  
Primary Root ◽  
Root Cap ◽  
Biologically Active ◽  
Root Tip ◽  
Mitochondrial Morphology ◽  
Secretory Vesicles ◽  
Secretory Product ◽  
Periconia Circinata ◽  
In Cells

Cytological and developmental effects induced by Periconia circinata toxin were examined to better understand the mechanism of action for this toxin. Roots of sorghum seedlings susceptible and resistant to P. circinata were incubated in 500 ng toxin/mL (treated) or water (controls). Root cap cells of resistant seedlings treated with the toxin were cytologically similar to those of controls, although the toxin caused a transient inhibition of mitosis in cells of the primary root tip. In outer root cap cells of susceptible seedlings treated for 0.25 h, hypersecretory activity was lost, secretory vesicles were fewer, and secretory product accumulated between the plasma membrane and cell wall. Also, inner root cap cells showed increased vacuolation. Longer treatments caused increased vacuolation, loss of starch, increased numbers of lipid bodies, pleomorphic amyloplasts, regularly stacked endoplasmic reticulum, apparent changes in the amounts of cytomembranes, dispersion of heterochromatin, and autolysis. Mitochondrial morphology was normal, but lesions in the tonoplast occurred before autolysis. The toxin also inhibited expansion and sloughing off of root cap cells and mitotic activity in the root tip. Stacked endoplasmic reticulum, nonhypersecretory dictyosomes, fewer secretory vesicles, increased vacuolation, reorganization of heterochromatin, and increased secretory product outside the protoplast were induced by P. circinata toxin and by cyanide. These data suggested that a cyanogenic compound is biologically active in cells treated with P. circinata toxin. Our results suggest that the toxin transiently affects resistant seedlings and in susceptible seedlings alters vacuolar expansion, secretory activity, and endomembrane flow, although other processes may also be affected.

scholarly journals The sites of synthesis and transport of extracellular polysaccharides in the root tissues of maize

1972 ◽  
Vol 130 (4) ◽  
pp. 1133-1145 ◽  
Author(s):  
Dianna J. Bowles ◽  
D. H. Northcote
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Rough Endoplasmic Reticulum ◽  
Secondary Wall ◽  
Extracellular Polysaccharide ◽  
Membrane System ◽  
Maize Root ◽  
Extracellular Polysaccharides ◽  
Root Tip ◽  
Root Cells

1. Subcellular fractionation of maize roots resulted in the isolation of the following enriched fractions: cell wall, dictyosome, smooth-membrane and rough-microsomal fractions. In addition, extracellular polysaccharide of the root slime was isolated. 2. Maizeseedling roots were incubated in vivo with d-[U-14C]glucose, and the pattern of incorporation of radioactivity into the polysaccharides of each fraction was investigated. 3. The differentiation of maize-root cells with respect to the synthesis of specific extracellular polysaccharide directly relates to the polysaccharide synthesized and transported within the membrane system of the cell. A fucose-containing polysaccharide, characteristic only of root slime, was present only in the membrane system of the root-tip region of the root. Regions of typical secondary wall development within the root were characterized by an increased incorporation of radioactivity into xylose of polysaccharide within the membrane system. 4. The incorporation of radioactivity into glucan polymers in the membrane fractions was very low in all regions of the root. Since in regions of secondary wall development greater than 60% of all radioactive incorporation was into a glucan polymer, it can be inferred that this polymer, most probably cellulose, is not synthesized or transported within the compartments of the membrane system. It is suggested that synthesis of cellulose occurs at the surface of the plasmalemma. 5. Maize-root cells contained 40 times more rough endoplasmic reticulum than dictyosome membrane. The relative specific radioactivities of each fraction indicated that polysaccharide was concentrated in the region of the Golgi apparatus, which showed a 100% increase in specific radioactivity compared with the rough endoplasmic reticulum. The Golgi apparatus can thus be regarded as a localized focal point on the synthetic and transport system of polysaccharide by the intracellular membrane compartments.

scholarly journals Preliminary research on lead absorption and translocation in root tip cells of Populus nigra "Italica" Moench.

2014 ◽  
Vol 57 (2) ◽  
pp. 217-222 ◽  
Author(s):  
Krystyna Idzikowska
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Adventitious Root ◽  
Apical Part ◽  
Populus Nigra ◽  
Root Tip ◽  
Lead Absorption ◽  
Preliminary Research ◽  
Tip Cells ◽  
Root Tip Cells

Observations were carried out to define the place of lead absorption within three regions of the poplar adventitious root tip (<em>Populus nigra</em> "Italica" Moench.) after 24-hour exposure to a solution of Pb(N0<sub>3</sub>)<sub>2</sub> (25 mg dm<sup>-3</sup> Pb). Deposits of lead were not observed in certain cells of the apical part of the meristem. In other cells, lead deposits were first observed in the lumen of several endomembrane compartments - the endoplasmic reticulum, dictyosomal stacks and nuclear envelope. Certain differences were noted in the amount of deposits in protoplasts with varied electron density. In the cells with greater deposits, lead was also observed in the cytoplasm, the mitochondria and the paramural bodies. Practically no lead precipitated in the cell wall. The presence of lead in the form of small deposit granules in the plasmodesmata may suggest transfer from cell to cell.

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