Cytochalasin B: effects on root morphogenesis in Allium cepa

1973 ◽  
Vol 51 (12) ◽  
pp. 2269-2273 ◽  
Author(s):  
D. des S. Thomas ◽  
N. M. Lager ◽  
E. K. Manavathu
Keyword(s):  
Allium Cepa ◽  
Root Length ◽  
Cytochalasin B ◽  
Morphological Changes ◽  
Cortical Cell ◽  
Root Tip ◽  
Metabolic Inhibitor ◽  
High Concentration ◽  
Cortical Cells ◽  
Cell Counts

Cytochalasin B (CB) applied at 30 μg/ml to seeds of onion, Allium cepa, from the start of imbibition, produced a reversible inhibition of mitosis and axis elongation. Inhibition appeared only after the 4th day and increased progressively thereafter. Mitotic inhibition by a 24-h pulse of CB applied to 6-day-old seedlings increased with root length. These results suggest that CB affects plant mitosis indirectly, possibly via inhibition of transport. CB did not produce polyploid or multinucleate cells.Cytochalasin B (30 μg/ml) supplied for 3 days to roots of onion bulbs, growing in water, produced morphological changes which are expressed here as percentages of the controls. Root length decreased (44%) while diameter increased (148%). Cortical cell lengths decreased (53%) and diameters increased (128%) when measured at 9 mm from the root tip. These compensatory changes resulted in comparatively minor decreases in root (97%) and cell (90%) volume, indicating that CB, even at the high concentration used, was not acting primarily as a general metabolic inhibitor. Cell counts along diameters at comparable distances, 130 cortical cells from the apical initial region, showed no change in the number of cells representing cortex and stele.

Computing with Self-Excitatory Cliques: A Model and an Application to Hyperacuity-Scale Computation in Visual Cortex

1999 ◽  
Vol 11 (1) ◽  
pp. 21-66 ◽  
Author(s):  
Douglas A. Miller ◽  
Steven W. Zucker
Keyword(s):  
Visual Processing ◽  
Network Architecture ◽  
Early Stage ◽  
Cortical Cell ◽  
Pyramidal Cells ◽  
Direct Calculation ◽  
Formal Theory ◽  
Cortical Cells ◽  
Cell Counts ◽  
Spatiotemporal Response

We present a model of visual computation based on tightly inter-connected cliques of pyramidal cells. It leads to a formal theory of cell assemblies, a specific relationship between correlated firing patterns and abstract functionality, and a direct calculation relating estimates of cortical cell counts to orientation hyperacuity. Our network architecture is unique in that (1) it supports a mode of computation that is both reliable and efficent; (2) the current-spike relations are modeled as an analog dynamical system in which the requisite computations can take place on the time scale required for an early stage of visual processing; and (3) the dynamics are triggered by the spatiotemporal response of cortical cells. This final point could explain why moving stimuli improve vernier sensitivity.

scholarly journals Domain-specific and cell type-specific localization of two types of cell wall matrix polysaccharides in the clover root tip.

1992 ◽  
Vol 118 (2) ◽  
pp. 467-479 ◽  
Author(s):  
M A Lynch ◽  
L A Staehelin
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Cellular Differentiation ◽  
Cortical Cell ◽  
Middle Lamella ◽  
Root Cap ◽  
Root Tip ◽  
Cortical Cells ◽  
Peripheral Cell ◽  
Clover Root

Using immunocytochemical techniques and antibodies that specifically recognize xyloglucan (anti-XG), polygalacturonic acid/rhamnogalacturonan I (anti-PGA/RG-I), and methylesterified pectins (JIM 7), we have shown that these polysaccharides are differentially synthesized and localized during cell development and differentiation in the clover root tip. In cortical cells XG epitopes are present at a threefold greater density in the newly formed cross walls than in the older longitudinal walls, and PGA/RG-I epitopes are detected solely in the expanded middle lamella of cortical cell corners, even after pretreatment of sections with pectinmethylesterase to uncover masked epitopes. These results suggest that in cortical cells XG and PGA/RG-I are differentially localized not only to particular wall domains, but also to particular cell walls. In contrast to their nonoverlapping distribution in cortical cells, XG epitopes and PGA/RG-I epitopes largely colocalize in the epidermal cell walls. The results also demonstrate that the middle lamella of the longitudinal walls shared by epidermal cells and by epidermal and cortical cells constitutes a barrier to the diffusion of cell wall and mucilage molecules. Synthesis of XG and PGA/RG-I epitope-containing polysaccharides also varies during cellular differentiation in the root cap. The differentiation of gravitropic columella cells into mucilage-secreting peripheral cells is marked by a dramatic increase in the synthesis and secretion of molecules containing XG and PGA/RG-I epitopes. In contrast, JIM 7 epitopes are present at abundant levels in columella cell walls, but are not detectable in peripheral cell walls or in secreted mucilage. There were also changes in the cisternal labeling of the Golgi stacks during cellular differentiation in the root tip. Whereas PGA/RG-I epitopes are detected primarily in cis- and medial Golgi cisternae in cortical cells (Moore, P. J., K. M. M. Swords, M. A. Lynch, and L. A. Staehelin. 1991. J. Cell Biol. 112:589-602), they are localized predominantly in the trans-Golgi cisternae and the trans-Golgi network in epidermal and peripheral root cap cells. These observations suggest that during cellular differentiation the plant Golgi apparatus can be both structurally and functionally reorganized.

Structural, chemical, and permeability changes following wounding in onion roots

1984 ◽  
Vol 62 (11) ◽  
pp. 2253-2259 ◽  
Author(s):  
G. J. Moon ◽  
Carol A. Peterson ◽  
R. L. Peterson
Keyword(s):  
Cell Walls ◽  
Cortical Cell ◽  
Root Tip ◽  
Cortical Cells ◽  
Calcofluor White ◽  
Suberin Lamellae ◽  
Histochemical Tests ◽  
Apoplastic Barrier ◽  
Tip Cells ◽  
Root Tip Cells

Onion roots were wounded by scoring them with a needle 80 to 120 mm proximal to the root tip. Cells in the region of the wound were studied immediately after wounding and daily for the next 6 days. By the 2nd day, cortical cells near the wound had produced pit callose and deposited suberin in their walls and air spaces. The amount of suberin deposited increased until 4 days after wounding. No suberin lamellae were observed in cortical cell walls, but histochemical tests and acid digestion confirmed the presence of suberin within the existing wall. Intercellular air spaces adjacent to the wound were totally occluded with an electron-dense material which had characteristics of suberin. Penetration studies using Calcofluor white M2R, a fluorescent apoplastic dye, showed that the wound was completely sealed 4 days after wounding. Thus, in response to wounding, nonlamellar suberin was deposited in the cortical cell walls and air spaces surrounding the wound and was continuous with the suberin present in the normal hypodermis, forming a complete apoplastic barrier.

Turgor, solute import and growth in maize roots treated with galactose

2004 ◽  
Vol 31 (11) ◽  
pp. 1095 ◽  
Author(s):  
Jeremy Pritchard ◽  
A. Deri Tomos ◽  
John F. Farrar ◽  
Peter E. H. Minchin ◽  
Nick Gould ◽  
...  
Keyword(s):  
Turgor Pressure ◽  
Cortical Cell ◽  
Root Tip ◽  
Pressure Probe ◽  
Similar Response ◽  
Fixed Carbon ◽  
Cortical Cells ◽  
Maize Roots ◽  
Before And After ◽  
Cell Turgor

It has been observed that extension growth in maize roots is almost stopped by exposure to 5 mm d-galactose in the root medium, while the import of recent photoassimilate into the entire root system is temporarily promoted by the same treatment. The aim of this study was to reconcile these two apparently incompatible observations. We examined events near the root tip before and after galactose treatment since the tip region is the site of elongation and of high carbon deposition in the root. The treatment rapidly decreased root extension along the whole growing zone. In contrast, turgor pressure, measured directly with the pressure probe in the cortical cells of the growing zone, rapidly increased by 0.15 MPa within the first hour following treatment, and the increase was maintained over the following 24 h. Both tensiometric measurements and a comparison of turgor pressure with local growth rate demonstrated that a rapid tightening of the cell wall caused the reduction in growth. Single cell sampling showed cell osmotic pressure increased by 0.3 MPa owing to accumulation of both organic and inorganic solutes. The corresponding change in cell water potential was a rise from –0.18 MPa to approximately zero. More mature cells at 14 mm from the root tip (just outside the growing region) showed a qualitatively similar response. Galactose treatment rapidly increased the import of recently fixed carbon (RFC) into the whole root as deduced by 11C labelling of photoassimilate. In contrast, there was a significant decrease in import of recently fixed carbon into the apical 5mm concomitant with the increase in turgor in this region. No decrease in import of recently fixed carbon was observed 5–15 mm from the root tip despite the increase in cortical cell turgor. These data are consistent with direct symplastic connections between the growing cells and the phloem supplying the solutes in the apical, but not the basal, regions of the growing zone. Hence, the inhibition of growth and the elevation of solute import induced by galactose are spatially separated within the root.

Sex-specifically responsive strategies to phosphorus availability combined with different soil nitrogen forms in dioecious Populus cathayana

2021 ◽  
Author(s):  
Xiucheng Liu ◽  
Yuting Wang ◽  
Shuangri Liu ◽  
Miao Liu
Keyword(s):  
Root Length ◽  
Root Length Density ◽  
Specific Root Length ◽  
P Uptake ◽  
Root Tip ◽  
P Availability ◽  
P Deficiency ◽  
Populus Cathayana ◽  
Leaf P ◽  
P Supply

Abstract Aims Phosphorus (P) availability and efficiency are especially important for plant growth and productivity. However, the sex-specific P acquisition and utilization strategies of dioecious plant species under different N forms are not clear. Methods This study investigated the responsive mechanisms of dioecious Populus cathayana females and males based on P uptake and allocation to soil P supply under N deficiency, nitrate (NO3 −) and ammonium (NH4 +) supply. Important Findings Females had a greater biomass, root length density (RLD), specific root length (SRL) and shoot P concentration than males under normal P availability with two N supplies. NH4 + supply led to higher total root length, RLD and SRL but lower root tip number than NO3 − supply under normal P supply. Under P deficiency, males showed a smaller root system but greater photosynthetic P availability and higher leaf P remobilization, exhibiting a better capacity to adaptation to P-deficiency than females. Under P deficiency, NO3 − supply increased leaf photosynthesis and PUE but reduced RLD and SRL in females while males had higher leaf P redistribution and photosynthetic PUE than NH4 + supply. Females had a better potentiality to cope with P deficiency under NO3 − supply than NH4 + supply; the contrary was true for males. These results suggest that females may devote to increase in P uptake and shoot P allocation under normal P availability, especially under NO3 − supply, while males adopt more efficient resource use and P remobilization to maximum their tolerance to P-deficiency.

scholarly journals Association of beta-cytoplasmic actin with high concentrations of acetylcholine receptor (AChR) in normal and anti-AChR-treated primary rat muscle cultures.

1984 ◽  
Vol 32 (9) ◽  
pp. 973-981 ◽  
Author(s):  
B W Lubit
Keyword(s):  
Acetylcholine Receptor ◽  
Acetylcholine Receptors ◽  
Neuromuscular Junctions ◽  
Morphological Changes ◽  
Muscle Cells ◽  
High Concentration ◽  
Rat Muscle ◽  
Cytoplasmic Actin ◽  
High Concentrations

Previous immunocytochemical studies in which an antibody specific for mammalian cytoplasmic actin was used showed that a high concentration of cytoplasmic actin exists at neuromuscular junctions of rat muscle fibers such that the distribution of actin corresponded exactly to that of the acetylcholine receptors. Although clusters of acetylcholine receptors also are present in noninnervated rat and chick muscle cells grown in vitro, neither the mechanism for the formation and maintenance of these clusters nor the relationship of these clusters to the high density of acetylcholine receptors at the neuromuscular junction in vivo are known. In the present study, a relationship between beta-cytoplasmic actin and acetylcholine receptors in vitro has been demonstrated immunocytochemically using an antibody specific for the beta-form of cytoplasmic actin. Networks of cytoplasmic actin-containing filaments were found in discrete regions of the myotube membrane that also contained high concentrations of acetylcholine receptors; such high concentrations of acetylcholine receptors have been described in regions of membrane-substrate contact. Moreover, when primary rat myotubes were exposed to human myasthenic serum, gross morphological changes, accompanied by an apparent rearrangement of the cytoplasmic actin-containing cytoskeleton, were produced. Although whether the distribution of cytoplasmic actin-containing structures was influenced by the organization of acetylcholine receptor or vice versa cannot be determined from these studies, these findings suggest that in primary rat muscle cells grown in vitro, acetylcholine receptors and beta-cytoplasmic actin-containing structures may be somehow connected.

Sunlight decreased genotoxicity of azadirachtin on root tip cells of Allium cepa and Eucrosia bicolor

2010 ◽  
Vol 73 (5) ◽  
pp. 949-954 ◽  
Author(s):  
W. Kwankua ◽  
S. Sengsai ◽  
C. Kuleung ◽  
N. Euawong
Keyword(s):  
Allium Cepa ◽  
Root Tip ◽  
Tip Cells ◽  
Root Tip Cells
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