ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1993.tb00686.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1993.tb00687.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1993.tb00688.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SUMMARYThe cell‐wall structure and the supramolecular organization of the plasma membrane in 29 species of red algae were studied both in replicas of rapidly frozen cells and in ultrathin sections.Most of the marine red algae investigated have a random distribution of the microfibrils of the cell walls; in a few cases there is a tendency to parallel alignment.Laurencia obtusais an exception in which apart from a random distribution, microfibrils are arranged parallelly in a certain wall layer. The microfibrils have a cylindric or ribbon‐like morphology. In a number of species, microfibrils consist of two, three or four linear subcomponents (sub‐fibrils). In certain species two or three microfibrils can be bundled.InErythrocladia subintegra, Radicilingua reptansandLaurencia obtusathe plasma membrane exhibits randomly distributed linear microfibril‐terminal complexes. All results favour the suggestion that the linear terminal complexes in the plasma membrane of the cells of the above mentioned species are involved in the biosynthesis, assembly and orientation of microfibrils. In the plasma membrane a number of other intramembranous particles are aggregated in various complexes (tetrads, complexes of six subunits, crystalline complexes, particle strings). Intramembranous particle complexes composed of four subunits ‘membrane tetrads’ have been observed in the plasma membrane and in the membranes of mucilage sacs of all red algae investigated. The ‘membrane tetrads’ are thought to be membrane‐bound multi‐enzyme complexes participating in the synthesis of the matrix polysaccharides.Observations of ultrathin sections suggest that the Golgi system and the inflated Golgi‐derived vesicles with fibrillar contents contribute to the formation of the wall.Our results support the view that the biosynthesis of cell‐wall skeletal and matrix polysaccharides in red algae

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1993.tb00689.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SUMMARYThe development and ultrastructure of cell walls of oil and mucilage cells in selected representatives of so‐called primitive and derived dicotyledons are summarized, and compared with information on cell walls in other idioblasts and secretory or protective tissues. Oil and mucilage cells ofCinnamomumandAnnona, and presumably other Laurales and Magnoliales, are both characterized by a suberized layer deposited against the primary wall. These taxa usually do not form mucilage or oil cavities through fusion of secretory cells.Hibiscusand other Malvales lack such a suberized layer in their mucilage cells and as a rule have mucilage cavities, resulting from the breakdown of common walls between mucilage cells.The inner, polysaccharide wall deposited against the suberized wall layer in oil cells strongly resembles the first deposited, dense mucilage layer in mucilage cells; the precise composition of these wall layers requires further study.It is hypothesized that, as in certain crystalliferous cells, laticifers, secretory trichomes, and epithelial cells of resin ducts, the suberized layer in oil and mucilage cells serves to compartmentalize the secretion product. In evolution the suberized layer may have been lost in mucilage cells in plant groups which possess exclusively mucilaginous secretory elements, and which are derived from ancestors with oil cells. However, an independent,de novo(parallel) origin of mucilage cells (and cavities) without suberized wall layers in derived and often unrelated dicotyledonous families may have been an alternative evolutionary pathwa

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1993.tb00690.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SUMMARYA detailed quantitative analysis on the orientation of the cortical microtubule arrays and the last layer of cellulose microfibrils deposited in the secondary cell wall has been performed onUrtica dioicaroot hairs.It was found that cortical microtubules of individual root hairs show a preferential orientation, which ranges in the total root hair population from − 20 to + 20° with respect to the longitudinal cell axis. Immunofluorescence and thin‐section preparations are comparable, as long as the individuality of the root hairs and the modal distribution of the microtubules in the root hairs are considered.The cellulose microfibrils in the secondary wall are organized in two steep helices. Quantitatively, the majority of the microfibrils are oriented in an S helix, while simultaneously a smaller group is arranged in a Z helix in the same root hair. It is concluded that microtubules do not directly control the orientation of nascent cellulose microfibrils in this complex texture. The organization of the secondary cell wall texture may be a variant of the organization of the primary cell‐wall t

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1993.tb00691.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SUMMARYThe behaviours are presented of newly‐synthesized xylan and putative glycine‐rich protein during patterned secondary cell‐wall biogenesis in drug‐treated tracheary elements (TEs) differentiating in culture from isolated mesophyll cells ofZinnia elegans. The normal secondary wall thickenings contain cellulose, xylan, and lignin, and the results reported here suggest that they also contain glycine‐rich protein (GRP). However, qualifications to this definitive interpretation are discussed. The specific cellulose synthesis inhibitors, 2,6‐dichlorobenzonitrile (DCB) and isoxaben, were applied near the onset of differentiation. When they were fully effective in inhibiting deposition of detectable cellulose in the thickenings, no labelling of the thickenings was observed with probes for xylan (xylanase and an antibody to xylose) or GRP (an antibody). When the drugs were partially effective, a small amount of detectable cellulose was still deposited in the thickenings. In such TEs, patches of xylan and GRP were observed between thickenings, suggesting that these components were exocytosed but not able to localize at the altered thickenings. A model for cell‐wall assembly is presented in which some molecules themselves are able to mediate the patterning of others, so that patterned secondary cell‐wall assembly partly occurs by a self‐per

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1993.tb00692.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SUMMARYParenchyma and sclerenchyma cell walls were mechanically isolated from sections of a newly extended maize internode containing cells at different stages of maturity. Internodes were divided into four equal segments (A[top]‐D[bottom]) and preparations of both cell types obtained from each segment. The lignin content of sclerenchyma (57.5–108.3 g kg−1) was greater than that of parenchyma (48.0–86.8 g kg−1) at all stages of development. The extent of lignification increased with age in both cell types but was similar in cells taken from segments A and B. The ratio of the saponifiable phenolic acids differed with age with levels of (E+Z)‐ferulic acid remaining essentially constant while the (E+Z)‐p‐coumaric acid content increased in parallel with lignification. The extent to which commercial ‘cellulase’ was able to degrade both cell types decreased with age and extent of lignification. Sclerenchyma walls were less degradable than parenchyma walls isolated from the same segment. The fitted rate constant calculated for the period 2–72 h, however, was independent of both age and cell type. The mean thickness of sclerenchyma walls increased with age because of secondary wall formation (confirmed by image analysis of sections prepared for microscopy) while parenchyma remained thin walled. The consequences of lignification appeared to be essentially the same for both cell types and, by implication, for both primary and

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1993.tb00693.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SUMMARYAnalyses of internodes from wheat taken at various times during maturation, and determination of theirin vitrodry matter digestibility confirmed that the decrease in digestibility could be attributed both to a progressive loss in cell contents and also to a marked decrease in cell‐wall digestibility. The latter was not easily explained by the changes in the proportion of the major wall components (cellulose, arabinoxylan and lignin), but may be explained in terms of the physical and chemical associations between wall polymers. Among these, covalent cross‐linking and bridging by hydroxycinnamic acids are important candida

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1993.tb00694.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

SUMMARYCell‐wall modifications in the root tissues surrounding the lateral emerging roots of leek were investigated using morphological andin situtechniques. Primordium meristem cell walls were thin with a weak gold labelling after treatments for pectin and cellulose localization, as already described in other plant meristems. By contrast, the surrounding tissues of the mother roots displayed deep changes: their walls were swollen, thickened, with large intercellular spaces. Specific probes revealed a distribution of cellulose molecules comparable to the undisturbed root and a substantial increase in pectic material. Cell‐wall remnants were at the interface between the emerging roots and the mother root. They were rich in pectic material, but not in cellulose. Other immunogold experiments located a polygalacturonase over the primordium cells and its interface with the mother root.It is suggested that lateral root morphogenesis involves controlled cell separation, thanks to a specific interaction between pectinolytic enzymes and pect

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1993.tb00695.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY