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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
301

Approche chronologique, territoriale et sociologique de la céramique préhistorique de Nubie (Mésolithique, Néolithique et Néolithique tardif, 2e-3e cataractes du Nil, Soudan) / Chronological, Territorial and Sociological Approach of the Prehistoric Pottery of Nubia (Mesolithic, Neolithic and Late Neolithic, 2nd-3rd cataracts of the Nile, Sudan)

Delattre, Hélène 26 November 2016 (has links)
Cette étude du matériel céramique provenant de la région située entre les 2e et 3e cataractes du Nil est anthropologique. Elle consiste dans un premier temps à établir un outil de classification permettant le diagnostic des sites dans lesquels la poterie a été mise au jour. Ce travail préliminaire conduit ensuite à aborder le corpus selon trois axes. Le premier est chronologique et aboutit à la construction de la séquence de l'occupation de Haute Nubie, et ce en trois étapes, céramique, culturelle et périodique. Le deuxième axe est territorial et remplit deux objectifs : d'abord déterminer les frontières des faciès et des cultures de la vallée du Nil moyen ; ensuite appréhender les dynamiques à l'échelle de l'Afrique du nord-est – qu'il s'agisse de diffusions d'objets et d'idées, de migrations de populations ou d'échanges marchands. La dernière partie est consacrée à l'approfondissement de quelques faits sociaux : d'abord l'imbrication du stockage, de la sédentarité et de la hiérarchie, ensuite le dépôt de mobilier dans les tombes, et enfin deux systèmes de croyances, en lien avec le monde animal et l'univers minéral. / This study of the pottery which was discovered in the region situated between the 2nd and the 3rd cataracts of the Nile is an anthropological study. First, it consists in building a classification tool which would help to diagnose the sites where the pottery was unearthed. This preliminary work leads to approach the corpus in three ways. First, the sequence of the occupation of Upper Nubia is built, in three stages: ceramics, cultures and periods. The second area of research is territorial and has two aims: to determine the boundaries of the facies and the cultures of the Middle Nile Valley, and to comprehend the dynamics across the Northeastern Africa – circulation of objects and ideas, migrations of populations, marketable exchanges. The last part is devoted to the study of some social facts: first, the interweaving of storage, sedentarity and hierarchy, then the deposition of artefacts in graves, and finally two systems of beliefs, in connection with the animal and the mineral world.
302

Seismic geomechanics of mud volcanoes

Gulmammadov, Rashad January 2017 (has links)
Mud volcanoes constitute an important component of petroliferous basins and their understanding is essential for successful exploration and development of hydrocarbon fields. They occur in both extensional and compressive tectonic settings, along with passive and active continental margins. Although extensive research exists on the geochemistry, geomorphology and stratigraphic evolution of these localized fluid flow structures, little is known about their geomechanical characteristics. This research investigates the geomechanics of mud volcanoes from the South Caspian Basin and West Nile Delta. This is achieved by establishing a workflow for geomechanical assessment of mud volcanoes using a P-wave velocity dataset from across the mud volcano within the offshore South Caspian Basin. This objective is developed further with the availability of seismic and wellbore data from around the Giza mud volcano, offshore West Nile Delta. Preliminary results of this study from the South Caspian Basin enable confidence in estimating the realistic magnitudes of elastic rock properties, stresses and fluid pressures from empirical and analytical correlations. Moreover, analysis of the variations in fluid pressures allow the fluid flow models around the mud volcano to be constrained and their gradients provide preliminary estimates of the drilling window. Structural and stratigraphic analysis around the Giza mud volcano offers insight into the formation of the mud volcano during the Quaternary and how the fault networks on the hanging wall of the arcuate tectonic fault have acted as conduits for primarily the pre-Pliocene fluids exploiting the areas of weakness along the hanging wall of the fault by entraining the Pliocene sediments. Fluid pressure evaluation reveals small overpressures caused by disequilibrium compaction. Further analysis offers insight into the critical fluid pressures that control fault movement, the stresses responsible for rock deformation around the wellbore and the width of the drilling window constrained by the fracturing of the strata. Analysis presented here provides details on the geomechanical significance of mud volcano environments, with implications for engineering practices. Overall, findings contribute to a systematic understanding of mud volcano settings not only from a field exploration and development point of view, but also at a wider scale for basin analysis and relatively small scale for play analysis.
303

Utilização de hidrolisado protéico de camarão em rações para tilápia do Nilo (Oreochromis niloticus, L.)

LEAL, Albino Luciani Gonçalves 15 February 2007 (has links)
Submitted by (edna.saturno@ufrpe.br) on 2017-02-06T16:53:46Z No. of bitstreams: 1 Albino Luciani Goncalves Leal.pdf: 575820 bytes, checksum: 4cc0fd6d3bf7fe9198563d35eae04f53 (MD5) / Made available in DSpace on 2017-02-06T16:53:46Z (GMT). No. of bitstreams: 1 Albino Luciani Goncalves Leal.pdf: 575820 bytes, checksum: 4cc0fd6d3bf7fe9198563d35eae04f53 (MD5) Previous issue date: 2007-02-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Aquaculture requires high-quality feeds with high protein content. So, the determination of less-expensive sources of protein which provides good growth is advantageous. Shrimp wastes have been identified as an animal protein source with great potential. Shrimp protein hydrolysate (SPH), a derived product obtained from shrimp wastes, was considered an excellent alimentary source and may serve as an useful source of protein and flavorants in food formulations. This work aimed to evaluate the nutritional quality of SPH through growth performance of juvenile Nile tilapia and its protein utilization. SPH was included in isonitrogenous diets at levels of 0, 5, 10 and 20% of fish meal protein replacement (SPH0, SPH5, SPH10 and SPH20) and offered to juvenile Nile tilapia (1.7±0.4 g) stocked in 40-L glass aquaria in a 45-day feeding trial. The inclusion of SPH did not produce statistical differences (P≥0.05) on final weight (27.18, 29.46, 26.02 and 25.19 g), survival (100%), relative weight gain (1,571, 1,624, 1,388 and 1,301%), average daily gain, ADG (0.57, 0.62, 0.54 and 0.52 g day-1), specific growth rate, SGR (7.15, 7.38, 6.85 and 6.73 % day-feed conversion ratio, FCR (1.15, 1.09, 1.13 and 1.17) and protein efficiency ratio, PER (2.26, 2.33, 2.20 and 2.14), respectively. The inclusion of SPH in diets for Nile tilapia statistically affected (P<0.05) the final fish body composition. Protein and ash contents decreased and fat content increased with SPH inclusion levels. This study clearly demonstrates that SPH could be included in diets for Nile tilapia without adverse effects on growth and protein utilization. / A produção aqüícola requer rações de alta qualidade, com alto conteúdo protéico. Assim, a determinação de fontes protéicas de menor custo e que promovam bom crescimento é benéfica. Resíduos de camarão têm sido identificados como uma fonte de proteína animal de grande potencial. Hidrolisado protéico de camarão (HPC) foi considerado como uma excelente fonte alimentar e pode servir como uma adequada fonte de proteína e flavorizante em formulações alimentares. Este trabalho objetivou avaliar a qualidade nutricional do HPC através do desempenho em crescimento de juvenis da tilápia do Nilo e sua utilização protéica. SPH foi incluído em dietas isoprotéicas em níveis de 0, 5, 10 e 20% de substituição da proteína advinda da farinha de peixe (HPC0, HPC5, HPC10 e HPC20) e ofertadas aos peixes (1,7±0,4 g) estocados em aquários de 40 L, por um período experimental de 45 dias. A inclusão do HPC não produziu diferenças estatísticas (P≥0,05) no peso final (27,18, 29,46, 26,02 e 25,19 g), sobrevivência (100%), ganho de peso relativo (1.571, 1.624, 1.388 e 1.301%), ganho de peso diário, GPD (0,57, 0,62, 0,54 e 0,52g dia-1), taxa de crescimento específico, TCE (7,15, 7,38, 6,85 e 6,73 % dia-conversão alimentar, CA (1,15, 1,09, 1,13 e 1,17) e eficiência protéica, EP (2,26, 2,33, 2,20 e 2,14), respectivamente. A inclusão do HPC nas dietas para a tilápia do Nilo afetou estatisticamente (P<0,05) a composição final dos peixes. Os teores de proteína e cinzas diminuíram e o teor de gordura aumentou com os níveis de inclusão do HPC. Este estudo claramente demonstra que o hidrolisado protéico de camarão pode ser incluído em dietas para a tilápia do Nilo sem efeitos adversos em crescimento e utilização protéica.
304

Estruturas vesiculares em misturas de surfactantes catiônicos

Alves, Fernanda Rosa [UNESP] 13 June 2008 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:30:54Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-06-13Bitstream added on 2014-06-13T19:19:37Z : No. of bitstreams: 1 alves_fr_dr_sjrp.pdf: 2029517 bytes, checksum: f737742cea44bc8699abdd17def3823d (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Estudos de calorimetria diferencial de varredura (DSC) e fluorescência de estado estacionário da sonda Vermelho do Nilo indicam a formação de vesículas de DODAX (X = Cl- ou Br-) em concentrações de surfactantes tão baixas quanto 10 µM. Estas vesículas foram denominadas microvesículas (µV), cuja Tm diminui monotonicamente com a concentração de DODAX até valores de Tm das vesículas tradicionais preparadas em 1.0 mM do surfactante. O efeito do contra-íon (Br- e Cl-) no comportamento termotrópico de fase das vesículas mistas de DODAB-DODAC foi investigado por DSC, condutimetria e espalhamento dinâmico de luz (DLS). Observou-se que a Tm aumenta sigmoidalmente de 45.8 a 48.9 oC com a fração molar de DODAC (xDODAC), com um ponto de inflexão no ponto eqüimolar. A condutividade e o diâmetro hidrodinâmico das vesículas variam muito pouco com xDODAB, indicando que a densidade superficial de carga das vesículas de DODAX é semelhante entre si, e o efeito do contra íon na Tm de DODAX se deve a interações específicas desses contra-íons na interface das vesículas. Medidas de DSC, fluorescência e turbidez de misturas de DODAB-DDAB indicam que as vesículas de DODAB têm maior afinidade por DDAB do que o oposto, resultando na formação de duas populações de vesículas mistas de DDAB-DODAB, com propriedades distintas. Além disso, medidas de fluorescência mostraram que a presença de pequena quantia de DODAB incorporado nas vesículas de DDAB causa um efeito significante na emissão da sonda devido ao aumento do tamanho das vesículas, sugerido por medidas de turbidez. O estudo dos sistemas DODAB/CnTAB/água na concentração total de surfactante igual a 1,0 e 5,0 mM, variando a concentração de CnTAB, e também mantendo a concentração de DODAB fixa em 1,0 mM, revelou uma forte dependência do comprimento da cadeia de hidrocarbonetos... / Differential scanning calorimetry (DSC) and fluorescence of the probe Nile Red studies reveal the formation of DODAX vesicles (X = Br- and Cl-) at surfactant concentrations as low as 10 µM. These vesicles were referred to as microvesicles (mV), whose Tm decreases monotonically with increasing DODAX concentration to the value for the ordinary vesicles at 1 mM. The effect of counterion (Br- and Cl-) on the thermotropic phase behavior of mixed DODAB-DODAC vesicles were investigated by differential scanning calorimetry (DSC), conductimetry and dynamic light scattering (DLS). Tm increases sigmoidally from 45.8 to 48.9 oC with DODAC molar fraction (xDODAC), with an inflection point at the equimolarity. The conductivity and the apparent hydrodynamic diameter vary little with xDODAB, indicating that the surface charge density is similar for DODAX, evidencing that the effect of counterion on Tm is due to the counterion specific interactions. DSC, fluorescence and turbidity measurements indicate a higher affinity of DDAB for DODAB vesicles than the reverse, resulting in two populations of mixed DDAB-DODAB vesicles with different properties. Besides, fluorescence measurements show that the presence of a small amount of DODAB in DDAB vesicles causes a pronounced effect on the Nile Red emission, due to the increase in vesicle size, as suggested from turbidity results. The study of DODAB/CnTAB/água systems at 1.0 and 5.0 total surfactant concentration, and varying CnTAB concentrations with constant 1.0 mM DODAB revealed a strong dependence of the chain length n and relative concentration of the surfactante in the properties of mixed DODAB-CnTAB vesicles. This study allowed analyzing the thermotropic phase behavior containing different amount of DODAB, and the mechanism of vesicle-micelle transition with increasing CnTAB concentration, below and above CMC... (Complete abstract click electronic access below)
305

Circulation enzootique du virus West Nile en population équine : identification de facteurs de risque environnementaux en Camargue, France

Pradier, Sophie 15 December 2010 (has links) (PDF)
L'objectif était d'évaluer le risque de circulation enzootique du virus West Nile (WN) chez le cheval en Camargue, région dans laquelle ce virus a déjà causé plusieurs épizooties. L'épidémiologie de la maladie de WN est très complexe, du fait de l'implication potentielle d'un grand nombre d'espèces de vecteurs et d'hôtes. De par sa transmission principalement vectorielle, la circulation du virus WN est fortement influencée par des facteurs environnementaux. L'espèce équine a été choisie comme témoin de la circulation du virus WN, car le cheval est particulièrement sensible à l'infection par ce virus. La méthode appliquée est basée sur l'utilisation du lien direct existant entre l'environnement et la circulation enzootique du virus WN, par l'étude de la séropositivité (IgG) chez le cheval. Dans les deux premières études présentées, certains facteurs de risque environnementaux ont été identifiés, comme des classes d'occupation du sol (zones agricoles hétérogènes, végétation inondée) ou des indices de paysage (Indice d'Imbrication et de Juxtaposition), ayant conduit à l'élaboration d'une carte de risque pour cette circulation dans le bassin méditerranéen français. Des facteurs de risque individuels, comme la race, l'âge et l'activité du cheval, ont également été identifiés. Dans la troisième étude présentée, des hypothèses de transmission du virus en Camargue ont été testées. Dans la région d'étude, le virus serait introduit par les oiseaux migrateurs et amplifié par Culex modestus et plusieurs espèces d'oiseaux compétentes. L'effet de dilution n'aurait pas d'impact sur l'amplification du virus en Camargue. Le virus serait transmis au cheval par C. modestus et C. pipiens.
306

Functional Analyses of West Nile Virus (WNV) Bicistronic Replicons Containing Different Sequence Elements and of Simian Hemorrhagic Fever Virus (SHFV) Polyprotein Processing

Radu, Gertrud Ulrike 29 November 2007 (has links)
The flavivirus West Nile virus (WNV) encodes a single polyprotein that is processed into three structural and seven nonstructural proteins. Various WNV bicistronic replicons that direct cap-dependent translation of an N-terminal viral capsid or capsid/Renilla luciferase fusion protein as well as IRES-dependent translation of the nonstructural proteins were constructed. An original replicon consisting of the WNV 5' NCR, the 5' 198 nts of the capsid coding sequence, which included the 5' cyclization sequence (Cyc), and an EMCV IRES followed by the WNV nonstructural genes and 3' NCR was generated. Real time qRT-PCR analysis of intracellular levels of this replicon RNA showed a 4 fold increase by 96 hr after transfection of BHK cells. Increasing the distance between the 5' Cyc and IRES by insertion of a 5' IRES flanking sequence alone or together with a Renilla luciferase reporter did not increase RNA replication. Addition of only a reporter decreased RNA replication. The insertion of an extended capsid coding sequence also did not enhance RNA replication, but did enhance both cap- and IRES-dependent translation of replicon RNA, as indicated by immunofluorescence and Western blot analysis. These results suggest the presence of a translation enhancer in the 3' portion of the capsid coding region. Simian hemorrhagic fever virus (SHFV) is a member of the family Arteriviridae, order Nidovirales. SHFV is unique among Nidoviruses in having three instead of two papain-like cysteine protease (PCP) motifs designated alpha, beta, and gamma, within the N-terminal region of its ORF1a. Mutations of putative PCP cleavage sites showed that the most efficient cleavage was by PCP beta at its downstream cleavage site. A large deletion located between the two catalytic residues of PCP alpha was hypothesized to render this protease inactive. However, processing was observed at the cleavage site following PCP alpha. Mutational analyses confirmed that PCP alpha is an inactive protease, and that the cleavage sites downstream of PCP alpha are cleaved by PCP gamma. When the catalytic residues of PCP gamma were mutated, PCP beta was also able to back cleave at these sites. This "back" cleavage is a previously unreported activity for an arterivirus PCP.
307

The ecology of infectious pathogens in a long distance migratory bird, the blue-winged teal (Anas discors): from individuals to populations

2013 May 1900 (has links)
The aim of this study is to improve our understanding of the ecology, spatiotemporal patterns, and risk of infectious pathogens of migratory waterfowl, using the blue-winged teal (Anas discors, BWTE), as a model. From 2007-2010, 1,869 BWTE were sampled in the prairie provinces (Alberta, Saskatchewan and Manitoba, Canada) to examine infection status and/or evidence of previous exposure to avian influenza virus (AIV), West Nile virus (WNV), and avian paramyxovirus-1 (APMV-1), in relation to host demographic variables (age, sex, body condition, exposure to other pathogens), other ecological variables such as local waterfowl breeding population density and local pond density, and year. The probability of AIV infection depended on an interaction between age and AIV antibody status. Hatch year birds with antibodies to AIV were more likely to be infected, suggesting an antibody response to an active infection. After hatch year birds with antibodies to AIV were less likely to be infected, suggesting immunity resulting from previous exposure. AIV infection was positively associated with local BWTE density, supporting the hypothesis of density dependent transmission. Exposure to WNV and APMV-1 were also associated with age and year. Furthermore, the probability of WNV exposure was positively associated with local pond density rather than host population density, likely because ponds provide suitable breeding habitat for mosquitoes, the primary vectors for transmission. We also investigated large-scale spatiotemporal trends in apparent prevalence of AIV across Canada and the United States throughout the year, using data from national avian influenza surveillance programs in Canada and the US in 2007-2010. Our analyses revealed that age, sex, year of sampling, flyway, latitude, and season (categorized by stages of the BWTE annual life cycle) were all important variables in predicting probability of AIV infection. There was an interaction between age and season. During late summer staging (August) and fall migration (September-October), hatch year birds were more likely to be infected than after hatch year birds, however there was no difference between age categories for the remainder of the year (winter, spring migration, and breeding season). Probability of infection increased non-linearly with latitude, and was highest in summer, corresponding to the beginning of fall migration when densities of birds and the proportion of susceptible hatch year birds in the population are highest. Birds in the Pacific, Central and Mississippi flyways were significantly more likely to be infected compared to those in the Atlantic flyway. Observed trends in seasonal, annual, and geographic patterns of AIV infection in BWTE across Canada and the US were primarily driven by the dynamics of AIV infection in hatch year birds. Our results demonstrate demographic as well as seasonal, latitudinal and flyway trends across Canada and the US. This research provided further evidence for the role of wild dabbling ducks, particularly BWTE, in the maintenance and ecology of AIV. This improved understanding of the role of BWTE as natural hosts, and the geographic, demographic and temporal variables that affect infection and transmission parameters, moves us closer to deciphering the overall ecology of the virus and its transmission and transportation pathways at the individual, population and continental levels. This knowledge, in turn, will permit development of better tools to predict and perhaps to prevent possible outbreaks in domestic animals as well as in humans.
308

Onion Root Anatomy and the Uptake of Sulphate and Phosphate Ions

Waduwara, Ishari 17 May 2007 (has links)
Ions in the soil solution traverse many layers (epidermis, exodermis, central cortex, and endodermis) within the root to reach the stele. The endodermis is present in almost all vascular plants while the exodermis is found only in majority of angiosperm roots tested. The maturation of the exodermis and the death of epidermis alter the plasma membrane surface areas (PMSA) potentially available for ion uptake. Do these changes reduce the ion uptake in proportion to the loss of absorptive surface areas? To answer this question onion (Allium cepa L cv. Wolf) adventitious root segments representing above features: Immature Exodermis Live Epidermis (IEXLEP), Mature Exodermis Live Epidermis (MEXLEP), Mature Exodermis Dead Epidermis (MEXDEP) were excised. Using a compartmental elution technique, radioactive sulphate and phosphate present in various internal compartments were quantified. Quantities of ions moved across the plasma membrane, a summation of quantities in the cytoplasm, ‘vacuole’, and ‘bound’ compartments, indicated that the maturation of the exodermis reduces the uptake of sulphate but not phosphate. In contrast, epidermal death reduced the movement of both ions across the plasma membranes. Although there is a reduction in the available PMSA with the maturation of the exodermis and death of the epidermis, these events do not necessarily reduce the ion movement into the plasma symplast. The endodermal cells of onion roots deposit suberin lamellae as secondary walls. As seen in cross-sections some cells remain without these lamellae and are known as ‘passage cells’. What is the pattern of suberin lamella deposition along the root? Is the suberin lamella a continuous layer? To answer these questions, endodermal layers isolated from onion adventitious roots were used in the present study. These layers were observed using four stains (Sudan Red 7B, Fluorol yellow 088 [Fy], berberine, and Nile red) and three microscopes (compound-white light, compound-epifluorescence and confocal scanning). In differentiating cells with and without suberin lamellae in endodermal layers Sudan Red 7B served the best results for compound-white light microscope, Fy for compound-epifluorescence microscope and Nile for confocal laser scanning microscope (CLSM). Suberin lamellae deposition initiated almost in a random manner; they continued to be deposited resulting in the production of longitudinal files alternating with files with passage cells, and were ultimately deposited in almost all cells at a distance of 255 mm from the tip. The suberin lamellae are perforated with pores, a consistent feature even as far as 285 mm from the tip. These pores may serve as portals for water, ions, and pathogen movement.
309

Regulation of Interferon Stimulated Genes in West Nile Virus Infected Mouse Embryofibroblasts

Pulit-Penaloza, Joanna A 05 May 2012 (has links)
The induction of type I interferon (IFN) and subsequent activation of interferon stimulated genes (ISGs) represent a first line of defense against viral infection. Typically type I IFN signaling leads to the phosphorylation of the STAT1 and STAT2 transcription factors (TFs) which then form a trimetric complex with IRF-9 and translocate to the nucleus to induce ISG expression. However, the results of this study showed that IFN-mediated upregulation of the ISG Oas1b, the product of which confers resistance to flavivirus induced disease, can be induced in a STAT1-independent manner. Since numerous ISGs have antiviral functions, many viruses have evolved strategies to disrupt the type I IFN-signaling pathway. In cases when STAT1 activation is blocked by a viral infection, STAT1-independent upregulation of ISGs provides an additional strategy for the cell to mount an effective antiviral response. Infection of mouse embryofibroblasts (MEFs) with West Nile virus (WNV) induced the production of IFN beta and STAT1 and STAT2 phosphorylation but blocked nuclear translocation and binding of these TFs to the promoters of the ISGs, Oas1a, Oas1a, Irf7 and Irf1. However, each of these antiviral ISGs was efficiently upregulated in infected cells and IRF-9 was shown to be crucial for the upregulation of Oas1a, Oas1b and Irf-7. IRF-3 or IRF-7 was needed to maintain the upregulation of these genes at later times of infection. In contrast, the upregulation of Irf1 by WNV infection did not depend on the tested IRFs but was reduced by inhibition of the p38 or NF-kappa B pathways. Although Irf1 mRNA was efficiently upregulated in WNV-infected cells IRF-1 protein synthesis was blocked. The precise mechanism of the IRF-1 translational suppression is not yet known, but the suppression was shown not to be due to increased proteasomal degradation of IRF-1 nor to alternative splicing of Irf1 mRNA. Preliminary results suggest miRNAs may play an indirect role in regulating IRF-1 translation. The results of this study expand knowledge about the strategies evolved by viruses to evade host cell antiviral responses and also provide valuable insights about alternative mechanisms utilized by the host cell to counteract viral infections.
310

Onion Root Anatomy and the Uptake of Sulphate and Phosphate Ions

Waduwara, Ishari 17 May 2007 (has links)
Ions in the soil solution traverse many layers (epidermis, exodermis, central cortex, and endodermis) within the root to reach the stele. The endodermis is present in almost all vascular plants while the exodermis is found only in majority of angiosperm roots tested. The maturation of the exodermis and the death of epidermis alter the plasma membrane surface areas (PMSA) potentially available for ion uptake. Do these changes reduce the ion uptake in proportion to the loss of absorptive surface areas? To answer this question onion (Allium cepa L cv. Wolf) adventitious root segments representing above features: Immature Exodermis Live Epidermis (IEXLEP), Mature Exodermis Live Epidermis (MEXLEP), Mature Exodermis Dead Epidermis (MEXDEP) were excised. Using a compartmental elution technique, radioactive sulphate and phosphate present in various internal compartments were quantified. Quantities of ions moved across the plasma membrane, a summation of quantities in the cytoplasm, ‘vacuole’, and ‘bound’ compartments, indicated that the maturation of the exodermis reduces the uptake of sulphate but not phosphate. In contrast, epidermal death reduced the movement of both ions across the plasma membranes. Although there is a reduction in the available PMSA with the maturation of the exodermis and death of the epidermis, these events do not necessarily reduce the ion movement into the plasma symplast. The endodermal cells of onion roots deposit suberin lamellae as secondary walls. As seen in cross-sections some cells remain without these lamellae and are known as ‘passage cells’. What is the pattern of suberin lamella deposition along the root? Is the suberin lamella a continuous layer? To answer these questions, endodermal layers isolated from onion adventitious roots were used in the present study. These layers were observed using four stains (Sudan Red 7B, Fluorol yellow 088 [Fy], berberine, and Nile red) and three microscopes (compound-white light, compound-epifluorescence and confocal scanning). In differentiating cells with and without suberin lamellae in endodermal layers Sudan Red 7B served the best results for compound-white light microscope, Fy for compound-epifluorescence microscope and Nile for confocal laser scanning microscope (CLSM). Suberin lamellae deposition initiated almost in a random manner; they continued to be deposited resulting in the production of longitudinal files alternating with files with passage cells, and were ultimately deposited in almost all cells at a distance of 255 mm from the tip. The suberin lamellae are perforated with pores, a consistent feature even as far as 285 mm from the tip. These pores may serve as portals for water, ions, and pathogen movement.

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