Microtubules and cell wall development in differentiating protophloem sieve elements of Triticum aestivum L

1987 ◽  
Vol 87 (4) ◽  
pp. 595-607
Author(s):  
E. P. ELEFTHERIOU
Keyword(s):  
Cell Wall ◽  
Triticum Aestivum L ◽  
Cellulose Microfibrils ◽  
Wall Material ◽  
Wall Thickening ◽  
Sieve Elements ◽  
Material Deposition ◽  
Cellulose Microfibril Orientation ◽  
Cell Wall Development ◽  
Developing Area

The densities of microtubules (MTs) along the lateral walls of developing sieve elements in root protophloem of wheat have been investigated by electron microscopy. They increase gradually in the very young sieve elements to reach a maximum just before the initiation of wall thickening. During wall increment MTs remain at high densities (more than 10 MTs μm−1), but their number declines abruptly when wall material deposition ceases. Cell wall thickening is not uniform: broad ridges alternate with narrow depressions, the latter occupied by plasmodesmata. During wall material deposition MTs overlie the thickenings only, being entirely absent from the non-thickened areas. The orientation of MTs reflects that of the currently deposited cellulose microfibrils in the cell wall, all being perpendicular to the direction of cell expansion. Numerous vesicles, apparently of Golgi apparatus origin, are encountered amongst the cortical arrays of MTs. Though the least spacing between the contiguous MTs is much smaller than the diameter of even the smallest vesicles, the latter were seen amongst the MTs, indicating that MTs do not prevent the vesicles from passing between them towards the developing area. All results favour the suggestion that MTs in sieve elements are involved in cell wall pattern development, cellulose microfibril orientation, and presumably in cell elongation.

Fine structure of tissue bordering lesions induced by wounding and virus infection

1978 ◽  
Vol 56 (23) ◽  
pp. 2990-2999 ◽  
Author(s):  
G. Faulkner ◽  
Warwick C. Kimmins
Keyword(s):  
Cell Wall ◽  
Fine Structure ◽  
Secondary Cell Wall ◽  
Wall Material ◽  
Wall Thickening ◽  
Pinto Bean ◽  
Local Lesions ◽  
Virus Localization ◽  
Similar Appearance ◽  
Secondary Cell Wall Thickening

Tissue in Phaseolus vulgaris L. cv. Pinto bean bordering local lesions induced by tobacco mosaic virus showed cell wall deposition associated with paramural body formation in a narrow ring of viable cells extending one to three cell diameters around the lesions. Deposition, which led to secondary cell wall thickening, was greatest 3–4 days after inoculation, the time when the lesion stopped expanding. Secondary cell wall thickening, of similar appearance but less pronounced, was seen in tissue bordering local lesions which continued to expand; no significant secondary cell wall thickening was observed in leaves with a nonlocalized infection. Cells bordering mechanical lesions differed markedly in fine structure from cells bordering virus and chemical lesions. It is suggested that the deposition of extra cell wall material in the wall regions of cells bordering fully expanded local lesions is associated with virus localization.

scholarly journals Hygroscopic swelling and shrinkage of latewood cell wall micropillars reveal ultrastructural anisotropy

2014 ◽  
Vol 11 (95) ◽  
pp. 20140126 ◽  
Author(s):  
Ahmad Rafsanjani ◽  
Michael Stiefel ◽  
Konstantins Jefimovs ◽  
Rajmund Mokso ◽  
Dominique Derome ◽  
...  
Keyword(s):  
Cell Wall ◽  
Growth Ring ◽  
Ion Beam ◽  
Microfibril Angle ◽  
Cellulose Microfibrils ◽  
Wall Material ◽  
Neighbouring Cell ◽  
Direction Parallel ◽  
Hygroscopic Swelling ◽  
S2 Layer

We document the hygroscopic swelling and shrinkage of the central and the thickest secondary cell wall layer of wood (named S2) in response to changes in environmental humidity using synchrotron radiation-based phase contrast X-ray tomographic nanoscopy. The S2 layer is a natural fibre-reinforced nano-composite polymer and is strongly reactive to water. Using focused ion beam, micropillars with a cross section of few micrometres are fabricated from the S2 layer of the latewood cell walls of Norway spruce softwood. The thin neighbouring cell wall layers are removed to prevent hindering or restraining of moisture-induced deformation during swelling or shrinkage. The proposed experiment intended to get further insights into the microscopic origin of the anisotropic hygro-expansion of wood. It is found that the swelling/shrinkage strains are highly anisotropic in the transverse plane of the cell wall, larger in the normal than in the direction parallel to the cell wall's thickness. This ultrastructural anisotropy may be due to the concentric lamellation of the cellulose microfibrils as the role of the cellulose microfibril angle in the transverse swelling anisotropy is negligible. The volumetric swelling of the cell wall material is found to be substantially larger than the one of wood tissues within the growth ring and wood samples made of several growth rings. The hierarchical configuration in wood optimally increases its dimensional stability in response to a humid environment with higher scales of complexity.

Studies of the structure and chemical composition of the cell walls of Vaucheriaceae and Saprolegniaceae

1963 ◽  
Vol 158 (973) ◽  
pp. 435-445 ◽  
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Insoluble Fraction ◽  
Water Soluble ◽  
Hot Water ◽  
Cellulose Microfibrils ◽  
Wall Material ◽  
Native Cellulose ◽  
A Cell ◽  
Crystalline Component

The cell walls of members of the Vaucheriaceae and Saprolegniaceae have been examined by X-ray analysis and electron microscopy, and their composition determined by hydrolysis and paper partition chromatography of the hydrolysates. Both differences and similarities between the members of these two species examined are found to supplement the comparative morphological and physiological information at present available. Saprolegnia , Achlya , Brevilegnia and Dictyuchus among the Saprolegniaceae possess hot-water soluble polysaccharides containing glucose residues only. This polysaccharide is not crystallographically identical with the polysaccharide found in Vaucheria sessilis with a similar solubility. The members of the Saprolegniaceae contain large amounts of alkali-soluble polysaccharides in contrast with the negligible amount found in V. sessilis . These polysaccharides are only weakly crystalline, but the indications are that the same polysaccharides may occur through­out the Saprolegniaceae. The alkali-insoluble wall material of Vaucheria species consists of highly crystalline native cellulose with large, apparently randomly arranged, microfibrils. The hydrolysate of this material contains ribose, xylose and arabinose in addition to glucose, presumably representing strongly bound pentosans. Native cellulose also occurs in the Saprolegniaceae but only in small proportion. The bulk of the alkali-insoluble fraction in the walls of these fungi appears amorphous in the electron microscope and is only weakly crystalline. It consists of one or m ore substances containing glucose, mannose, ribose and possibly other sugars together with traces of glucosamine. These substances presumably cover the cellulose microfibrils. The total quantity of non-cellulosic polysaccharide in the Saprolegniaceae approaches 85% of the total wall weight in contrast with the situation in Vaucheria where the cellulose alone approaches 90% of the total cell wall. Dichotomosiphon is unique among the organism s studied in this paper, in possessing a cell wall entirely soluble in alkali and composed of approximately equal quantities of glucose and xylose. The crystalline component is aβ-1,3-linked xylan, as already reported for some of the Siphonales (closely related algae) by Frei & Preston.

Mechanistic modelling of the influence of temperature on the wood anatomy of Scots pine

2020 ◽  
Author(s):  
Andrew Friend
Keyword(s):  
Tree Ring ◽  
Scots Pine ◽  
Wood Anatomy ◽  
Mass Density ◽  
Mechanistic Explanation ◽  
Wall Material ◽  
Wall Thickening ◽  
Maximum Latewood Density ◽  
Material Deposition ◽  
Latewood Density

<p>Despite its importance for the study of past climates, as well as its significance for carbon sequestration, we lack a mechanistic explanation for how temperature controls wood anatomy. A model of xylogenesis is presented and used to analyse observed tree ring anatomy-temperature relationships in Scots pine (<em>Pinus sylvestris</em>). The model treats the daily proliferation of new cells in the cambium and their subequent differentiation through expansion and secondary wall thickening phases. Control on size at division in the cambium follows recent work on the <em>Arabidopsis</em> shoot apical meristem, and cell enlargement rates in the cambium and enlargement zone are controlled by temperature. The duration of post-cambial enlargement is partially controlled by the rate at which cells pass through the enlargement zone, and partially by the size of this zone, which is controlled by daylength. This set of assumptions is sufficient to generate observed profiles of cell sizes across radial files, with characteristic transitions from earlywood to latewood. After they leave the enlarging zone, cells enter the wall thickening zone, the width of which is also dependent on daylength. A temperature-dependent rate of wall material deposition is insufficient to reproduce the observed gradient in mass density across the radial file, and fails to fully capture the observed seasonality of the correlation between maximum latewood density and temperature. Inclusion of a control on the rate of wall deposition from substrate (sugar) supply, diffusing from the phloem across the radial file, corrects these deficiencies. The resulting model provides a mechanistic explanation of temperature-tree ring relationships, and has the potential to underpin understanding of how climate and CO<sub>2</sub> interact in determining the amount of carbon sequestered in trees.</p>

Light and electron microscopy studies on the infection of tomato fruits by Botrytis cinerea

1980 ◽  
Vol 58 (12) ◽  
pp. 1394-1404 ◽  
Author(s):  
F.H. J. Rijkenberg ◽  
G. T. N. De Leeuw ◽  
K. Verhoeff
Keyword(s):  
Electron Microscopy ◽  
Cell Wall ◽  
Host Cell ◽  
Botrytis Cinerea ◽  
Light And Electron Microscopy ◽  
Microscopy Study ◽  
Wall Material ◽  
Wall Thickening ◽  
Cell Organelles ◽  
Tomato Fruits

A light microscopy study of the host–parasite relationship of Botrytis cinerea on immature tomato fruits was combined with an electron microscopy examination. Both techniques indicate that the cuticle is dissolved enzymatically rather than ruptured mechanically. Inter- and intracellular hyphae have no apparent effect on the cuticle, but do break down wall material. If the penetration tube development is arrested after emerging from the cuticle into the wall, wall discolouration and wall thickening become evident and a considerable increase in host cell organelles below the penetration site is observed. A papilla is also apposited. At successful penetration, when the hypha emerges from the cell wall into the host cell, little cell wall discolouration at the infection site is evident, but the cytoplasm becomes degenerate. Further hyphal extension then occurs in the epidermis, killing more epidermal cells, and leading to collapse, but not penetration, of underlying tissue.

scholarly journals Histone methyltransferase ATX1 dynamically regulates fiber secondary cell wall biosynthesis in Arabidopsis inflorescence stem

2020 ◽  
Author(s):  
Xianqiang Wang ◽  
Denghui Wang ◽  
Wenjian Xu ◽  
Lingfei Kong ◽  
Xiao Ye ◽  
...  
Keyword(s):  
Cell Wall ◽  
Secondary Wall ◽  
Histone Methyltransferase ◽  
Epigenetic Mechanism ◽  
Wall Thickening ◽  
Loss Of Function ◽  
Inflorescence Stem ◽  
Secondary Wall Thickening ◽  
Cell Wall Development ◽  
Stem Development

Abstract Secondary wall thickening in the sclerenchyma cells is strictly controlled by a complex network of transcription factors in vascular plants. However, little is known about the epigenetic mechanism regulating secondary wall biosynthesis. In this study, we identified that ARABIDOPSIS HOMOLOG of TRITHORAX1 (ATX1), a H3K4-histone methyltransferase, mediates the regulation of fiber cell wall development in inflorescence stems of Arabidopsis thaliana. Genome-wide analysis revealed that the up-regulation of genes involved in secondary wall formation during stem development is largely coordinated by increasing level of H3K4 tri-methylation. Among all histone methyltransferases for H3K4me3 in Arabidopsis, ATX1 is markedly increased during the inflorescence stem development and loss-of-function mutant atx1 was impaired in secondary wall thickening in interfascicular fibers. Genetic analysis showed that ATX1 positively regulates secondary wall deposition through activating the expression of secondary wall NAC master switch genes, SECONDARY WALL-ASSOCIATED NAC DOMAIN PROTEIN1 (SND1) and NAC SECONDARY WALL THICKENING PROMOTING FACTOR1 (NST1). We further identified that ATX1 directly binds the loci of SND1 and NST1, and activates their expression by increasing H3K4me3 levels at these loci. Taken together, our results reveal that ATX1 plays a key role in the regulation of secondary wall biosynthesis in interfascicular fibers during inflorescence stem development of Arabidopsis.

Microtubules and lithocyst morphogenesis in Pilea cadierei

1989 ◽  
Vol 67 (9) ◽  
pp. 2788-2804 ◽  
Author(s):  
B. Galatis ◽  
P. Apostolakos ◽  
E. Panteris
Keyword(s):  
Central Region ◽  
Cellulose Microfibrils ◽  
Wall Material ◽  
Wall Thickening ◽  
Cylindrical Wall ◽  
Periclinal Wall ◽  
Wall Ingrowth ◽  
Microtubule Formation ◽  
Parallel Fashion

Lithocysts in Pilea cadierei are initiated by differential divisions, the plane of which is predicted by typical preprophase microtubule bands. They soon become polarized and undergo a unique differentiation. The external periclinal wall thickens considerably in the absence of microtubules. In incipient lithocysts, a periclinal band of microtubules lines the external ends of the anticlinal walls. A distinct local thickening, possessing periclinal cellulose microfibrils, underlies the microtubule band. The cystolith stalk originates as a cylindrical wall ingrowth of a limited central region of the external periclinal wall. This grows inwards in the absence of microtubules in a preformed cytoplasmic diaphragm, approaching the internal periclinal wall. Stalk formation as well as the external periclinal wall thickening are not affected by colchicine and isopropyl n(3-chlorophenyl) carbamate. A cystolith body is formed within a cytoplasmic diaphragm in which most of the lithocyst organelles are located; this body is rich in cellulose microfibrils and is formed by the deposition of large amounts of wall material at the free end of the stalk, at right angles to its axis. This morphogenetic shift is preceded by the formation of a system of microtubules that converge in cortical sites close to the stalk. They proliferate and form an axial sheath around the cystolith body. The cellulose microfibrils are aligned in a parallel fashion with microtubules. Microtubule destruction by colchicine results in malformation of both the lithocyst and the cystolith body. Aberrant cystolith bodies are also formed in the presence of isopropyl n(3-chlorophenyl) carbamate, which seems to interfere with microtubule formation. These observations suggest that the lithocyst – cystolith body morphogenesis is controlled by microtubules.

Aerial root cap structure of an orchid, Epidendrum

1981 ◽  
Vol 59 (9) ◽  
pp. 1702-1708 ◽  
Author(s):  
Susan J. Blackman ◽  
Edward C. Yeung
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Cell Walls ◽  
Root Cap ◽  
Wall Material ◽  
Wall Thickening ◽  
Cell Wall Material ◽  
Random Orientation ◽  
Mitotic Figures ◽  
Distal Cell

The root cap of Epidendrum ibaguense has a rounded profile with a root cap junction present between the cap and meristem. A distinct columella region is lacking. Mitotic figures are infrequent in the root cap initial cells. The root cap initials and their immediate derivatives show few dictyosomes, little endoplasmic reticulum, plastids lacking starch, and few vacuoles. As the cells age they increase in size and show increasing vacuolation. Plastids increase by division and accumulate large starch grains. Throughout the root cap, amyloplasts maintain a random orientation in the cell. Endoplasmic reticulum also becomes more abundant as the cells age. In older cells, hypertrophied dictyosomes are evident and cell wall material begins accumulating between the distal cell wall and the plasmalemma. Wall thickening progresses with age though radial walls remain largely unthickened. Vacuolation progresses and is followed by complete senescence leaving only the cell walls.

The mechanism of surface growth in parenchyma of Avena coleoptiles

1955 ◽  
Vol 3 (2) ◽  
pp. 137 ◽  
Author(s):  
AB Wardrop
Keyword(s):  
Cell Wall ◽  
Tip Growth ◽  
Cell Types ◽  
Cellulose Microfibrils ◽  
Wall Material ◽  
Cell Wall Material ◽  
Cell Enlargement ◽  
Electron Microscopic ◽  
Stages Of Growth ◽  
Preferred Direction

A study has been made of the organization of the cell wall in the parenchyma of Avena coleoptiles at successive stages of growth, using light and electron microscopic methods. It has been observed that extension of the parenchyma involves a progressive separation of the primary pit fields accompanied by an increasing dispersion of the cellulose microfibrils about their preferred direction of orientation. On the basis of this, and ancillary evidence from other cell types, it is suggested that extension growth involves stretching of the cell with the intercalation of new microfibrils into the expanding cell wall framework from the regions of the primary pit fields and penetration of the cell wall by plasmodesmata. It is considered that the evidence is consistent equally with the view either that the cell wall is stretched as water absorption accompanying enlargement takes place, or that cell enlargement is controlled by the synthesis of cell wall material at synthetic centres (pit fields and plasmodesmata) distributed over the cell surface. The concept of bipolar tip growth for coleoptile parenchyma is rejected.

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