In this study, the feasibility of a NaA zeolite membrane for the gas phase separation of steam and hydrogen mixtures was determined. The Fischer-Tropsch (FT) process, which produces high value fuels and chemicals from coal and natural gas, can be greatly improved upon by the selective removal of water from the FT reactor product stream. According to the FT reaction kinetics, the rate of reaction increases with the partial pressure of hydrogen but is adversely affected the presence of water in the reactor product stream. Chemisorbed water on the surface of the metal catalysts also enhances deactivation due to sintering and fouling. The use of a zeolite membrane reactor is well equipped to serve the purpose of in-situ water removal as it can facilitate the separation of chemical components from one another in the presence of catalytic reactions. The LTA type zeolite membrane NaA or zeolite 4A, in particular, is well suited for the separation of polar (H2O) from non-polar (H2) molecules because of its high hydrophilicity. NaA has also been identified as an excellent candidate for selective water removal applications due its high adsorption affinity and capacity for water. The NaA membrane used in this study was manufactured by means of the in-situ crystallisation method where the growth of crystals on the inside surface of a centrifugally casted a-alumina support was favoured. Scanning electron microscopy (SEM) analyses performed on the membrane after a double hydrothermal synthesis indicated that the surface topology was rough and that the zeolite crystals formed were not uniform in size. Overall, the membrane thickness varied between 6.5 and 8.0 flm. An evaluation of the membrane quality was made possible through permeation experiments involving SF6 and Hz. The calculated Hz/SF6 permselectivity in this study was found to be 9.78, which despite being higher than the Knudsen diffusion selectivity of 8.54, confirmed the presence of intercrystalline defects or non-zeolitic pores in the membrane. Experiments concerning pure component and binary mixture permeation of steam and hydrogen through the supported NaA membrane were conducted over a temperature range of 115°C to 160 °c for binary hydrogen/steam mixtures, 25°C to 160°C for pure hydrogen and 130°C to 170°C for pure steam. For the permeation of pure component hydrogen, a local maximum in its permeance having a value of 224 x 10'°8 mol.m,z.s'!.Pa'! was reached at a system pressure and temperature of 6.875 bar and 75°C respectively. For the permeation of pure component steam through NaA, the effects of capillary condensation in the pores and defects of the zeolite membrane resulted in a decrease in steam permeance as a function of absolute pressure for temperatures lower than 160 °c. Once the effects of capillary condensation had receded, maxima in the steam permeances as a function of temperature corresponding to values of 70 x 10,08, 65 X 10,08 and 75 x 10,08 mol.m•2.s'I.Pa'l were found for the 182.5, 197.5 and 222.5 kPa isobars respectively. These observations collaborated well with the description of surface diffusion with permeation taking place in the Langmuir (strong adsorption) regime. Permeation experiments through NaA as function of temperature were conducted for a 90 mol% steam -10 mol% hydrogen (90-10) binary mixture as well as for a 60-40 mixture of these two. At low temperatures the permeation of hydrogen was completely suppressed by the condensed steam resulting in an almost perfect separation. The Kelvin equation was used to estimate the pore size of the defects which was found to range between 1.86 and 2.45 nm. The temperature range over which these defects in the membrane were assumed to become unblocked (i.e. assuming when the first breakthrough of hydrogen occurred), were determined to be between 140 to 148 °c and between 128 to 130 °c for the 90-10 and 60-40 mixtures respectively. The mixture selectivities (towards water) between 115 °c and 130 °c were found to be immensely high (much greater than 1000) for both the 90-10 and 60-40 mixtures, while the ideal selectivities were calculated to be less than lover the same temperature range. At 140 °c, the selectivity towards water for the 9010 mixture was still greater than 1000; however for the 60-40 mixture at this temperature, an inversion of selectivity towards H2 had already taken place. The breakthrough in H2 permeance occurs at a much lower temperature when the feed mixture contains a lower concentration of water. Since the partial pressure of steam will be reduced, larger pores will become unblocked at lower temperatures according to the Kelvin equation. / Thesis (M. Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2008.

Web applications are often described as being cross-platform. They are accessible from a multitude of different web browsers, which in turn are running on a multitude of different operating systems. For a time now, developers have used many different tools to create cross-platform applications for mobile devices with web technologies. However, these applications fail to deliver when taken out of their native environment, and often do not feel native at all. Enter Progressive Web Applications, PWA. PWA’s are applications written for the web with web technologies, running in a browser,  but seasoned with some techniques that can make them behave like a native application when running on a mobile device. They are just ordinary web applications with native behaviour such as offline support, installability, and push notifications. The question that arises is - can this new type of web applications match Native Android Applications in performance, especially the response time when accessing the device's hardware? This report will try to answer that question

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Phytohormone auxin plays an important role in regulating plant development. Directional (polar) cell-to-cell auxin transport creates auxin gradients within plant tissues, which trigger a specific developmental response. The vast majority of available data concerns angiosperms. Lower land plants have been much less explored in this regard, but the important auxin-related mechanisms (including polar auxin transport) are already present in mosses. To uncover the origins of auxin action, one must focus on green algae, especially of clade Streptophyta, which are the direct ancestors of all land plants. In this study, the possible effects of auxins, both native and synthetic, were investigated on two algae: basal, unicellular Chlorella lobophora and advanced, filamentous Spirogyra sp. The latter received comparably more attention, since it belongs to a clade now acknowledged as a sister group to land plants. Chlorella lobophora culture growth was irresponsive to synthetic auxin NAA. The average Spirogyra sp. cell length was, however, changed by auxins at high concentrations. By conducting accumulation assays of radioactively labelled auxins and HPLC analysis, auxin metabolism and transport was investigated in Spirogyra sp. This alga was able to metabolize the plant-native IAA, but not synthetic auxins...

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The aim of this work was to study the vegetative propagation of louro-pardo (Cordia trichotoma (Vell.) Arrab. ex Steud.) from root cuttings and minicuttings. Three trials were conducted. The first trial, roots were gotten from adult trees of louro-pardo. Root cuttings with 5.0 cm of length were classified in two diameters: thick (2.0 - 3.0 cm) and thin (< 2.0 cm). The root cuttings were immersed for 10 s. in an indolbutiric acid (IBA) solution of 0, 4000, 8000 or 12000 mg L-1. At 180 days, the percentages of sprouting and rooting, the number and length of shoots and roots were evaluated. Root cuttings from adult trees of louro-pardo showed 1.25% of sprouting, but they did not root. The second trial, root cuttings were gotten from three year-old plants of louro-pardo and root cuttings classified in small (1.0 - 1.5 cm) and large (1.6 - 2.5 cm) and immersed for 10 s. in an IBA solution of 0, 2000, 4000 or 6000 mg L-1. At 30 and 60 days, the percentages of rooted cuttings; sprouted cuttings; and survival of cuttings; the number and length of sprouted and rooted cuttings were evaluated. Root cuttings treated with 6000 mg L-1 of IBA had the best response in terms of sprouting and rooting. Large root cuttings showed the highest percentage of sprouting (26%), the highest number of sprouts (0.30) and the longhest sprouts and roots (2.27 and 5.40 cm) at 60 days of evaluation. The third trial, root cuttings were classified according to the position in the root system as basal, medium and apical. Cutting measuring 1.0; 3.0 or 5.0 cm of length were immersed for 10 s. in an IBA solution of 6000 mg L-1. At 60 and 90 days, the percentages of rooted and sprouted cuttings; and survival; the number and length of sprouted and rooted cuttings were evaluated. Basal and medium cuttings had the best response in terms of sprouting and rooting. Root cuttings measuring 3.0 and 5.0 cm were better than those with 1.0 cm of length. In this study, we also carried out trials with minicuttings of louro-pardo. The first trial, ministumps from plantlets of asexual and seminal origin with six and 12 month-old were fertilized with different nutrient solutions. The production of minicuttings per ministump was evaluated after 30 and 60 days. Minicuttings from these ministumps were treated or not with 1000 mg L-1 of naphthalene acetic acid (NAA). At 30 days, the percentage of sprouting, rooting and survival; the number of sprouts; and the number and length of roots were evaluated. The second trial, minicuttings from ministumps of asexual and seminal origin were treated or not with 2000 mg L-1 of IBA. The same evaluations were done at 30 and 60 days. The concentration of the nutrient solution did not affect the production of minicuttings per ministumps. The concentrations of NAA and IBA did not affect minicutting rooting. Overall, ministumps from asexual origin showed adequate capability for vegetative propagation of louro-pardo. These ministumps have the highest production of minicutting associated with the highest rooting potential without any treatment. / O objetivo deste estudo foi avaliar a propagação vegetativa de louro-pardo (Cordia trichotoma (Vell.) Arrab. ex Steud.) por estaquia radicular e miniestaquia. Foram realizados três experimentos de estaquia radicular. No primeiro experimento, raízes de árvores adultas de louro-pardo foram seccionadas em estacas com 5,0 cm de comprimento e classificadas quanto ao diâmetro em grossas (2,0 - 3,0 cm) e finas (< 2,0 cm). As estacas radiculares foram tratadas em solução de 0, 4000, 8000 ou 12000 mg L-1 de ácido indolbutírico (AIB). Aos 180 dias, avaliaram-se as porcentagens de brotação e enraizamento, o número e comprimento de brotos e raízes. Estacas radiculares adultas de louro-pardo apresentaram 1,25% de brotação e não formaram raízes. No segundo experimento, raízes de plantas de louro-pardo de origem seminal e com três anos de idade foram seccionadas em estacas com 5,0 cm de comprimento, classificadas quanto ao diâmetro em grossas (1,6 - 2,5 cm) e finas (1,0 - 1,5 cm) e tratadas em solução de 0, 2000, 4000 ou 6000 mg L-1 de AIB. Aos 30 e 60 dias, avaliaram-se as porcentagens de brotação e enraizamento, a sobrevivência das estacas, o número e o comprimento de brotos e raízes. Estacas radiculares juvenis, tratadas em solução de 6000 mg L-1 de AIB, apresentaram a maior porcentagem de enraizamento e o maior número de raízes, aos 30 e 60 dias. Estacas radiculares grossas apresentaram a maior porcentagem de brotação (26%), o maior número de brotos (0,30) e o maior comprimento de brotos e raízes (2,27 e 5,40 cm), aos 60 dias de avaliação. No terceiro experimento, raízes de plantas de louro-pardo de origem seminal e com três anos de idade foram classificadas quanto à posição de coleta em basais, medianas e apicais, seccionadas em estacas de 1,0; 3,0 e 5,0 cm de comprimento e tratadas com 6000 mg L-1 de AIB. Aos 60 e 90 dias, avaliaram-se as porcentagens de brotação e enraizamento, a sobrevivência das estacas, o número e comprimento de brotos e raízes, e o comprimento de brotos e raízes por volume de estaca. Estacas radiculares juvenis basais e medianas apresentaram as melhores respostas de enraizamento, aos 60 e 90 dias. Estacas radiculares juvenis com 3,0 e 5,0 cm de comprimento se mostraram superiores às estacas radiculares com 1,0 cm. Neste estudo, também foram conduzidos experimentos de miniestaquia de louro-pardo. No primeiro experimento, minicepas de origem assexuada e de origem seminal foram fertirrigadas com diferentes concentrações de solução nutritiva. A produção de miniestacas por minicepa foi avaliada aos 30 e 60 dias. Para o enraizamento, as miniestacas foram tratadas ou não em solução de 1000 mg L-1 de ácido naftalenoacético (ANA). Aos 30 dias, avaliaram-se as porcentagens de brotação e enraizamento, a sobrevivência das miniestacas, o número e comprimento de brotos e raízes. No segundo experimento, miniestacas com e sem folhas obtidas de minicepas de origem assexuada e seminal foram tratadas ou não com 2000 mg L-1 de AIB. Aos 30 e 60 dias, foram avaliadas as variáveis descritas anteriormente. A concentração da solução nutritiva não influenciou a produção de miniestacas/minicepas. O uso de ANA e AIB não afetou o enraizamento das miniestacas. As minicepas de origem assexuada mostraram-se adequadas à propagação vegetativa de louro-pardo, pois apresentaram maior produtividade em minijardim clonal associada ao maior potencial de enraizamento das miniestacas, sem a necessidade de tratamento com auxina.

This study had as objective to study the in vitro regeneration of cedar (Cedrela fissilis Vell.), a native tree of economic interest, belonging to Meliaceae family. For seeds desinfestation, different treatments with sodium hypochlorite in different concentration and immersion times were tested combined with differents culture mediums. To establish the nodal segments in vitro, benlate at 300 mg.l-1 and streptomicine sulphate at 10 mg.l-1 were added to the culture medium WPM reduced to ¾ of its salts concentration, isolated or not. After that, the hypocotyl segments from the 30 days in vitro cultured plants were used as explant in sprouts multiplication in culture mediums MS and WPM combined or not with the cytokinins BAP and KIN at 5μM.l-1 . It was also tested, in hypocotyl segments, the influence of BAP (0; 1,25; 2,5 and 5,0 μM.l-1) combined with the IBA or NAA (0,55μM.l- 1), in culture medium WPM during two subcultives. 60 days hypocotyl segments from cultive in BAP (0;1,25; 2,5 and 5,0 μM.l-1) were transferred to WPM medium added of only GA3 at 3μM.l-1 remaining during more than 30 days. Seeds desinfestated with sodium hypochlorite at 2% during 10 minutes showed a lower index of fungal contamination (8,7%) and the higher index of germination (80%), the mediums MS and WPM allowed the germination of 72,5%. The nodal segments from 3 years old plants showed an average index of bacterial contamination (13% 21 days after the inocultation) when cultivated in WPM culture medium added of benlate (300mg.l-1) plus streptomicine sulphate (10 mg.l-1) and survival index of 83%. The explants from the hypocotyl region showed average indexes of regeneration of 2,8 when cultivated in WPM medium supplemented with BAP at 5μM.l-1, on the other hand, in MS medium, the average tax of formation was 2,5 sprouts per explant. When tested in WPM culture medium, in different BAP concentrations, only at 30 days of cultive there was an interaction between the cytokinins doses and the presence of auxins IBA and NAA. BAP at 5μM showed explants with higher taxes of multiplication, regardless the auxins addition to the culture medium. In the following subcultives there was not an interaction between the concentrations and the effect of auxin presence, where the medium without auxin, associated to BAP at 5μM, promoted a higher average of sprouts per explant 2,29 (60 days). The average number of knots at 30 days of cultive was of 2,84 when evaluated the medium with ANA plus 2,5μM of BAP. At 60 days, the culture medium without the auxine promoted an average of 4,15 knots per explant, differing statistically from the mediums with auxin. At 90 days, the number of knots were 5,59 when BAP was used at 5μM plus IBA. The average length of the sprouts in the medium with NAA showed to be the more efficient (0,86 cm) at 30 days of cultive. At 60 days, the average length of the sprouts was of 0,95 and, at 90 days the average length of the sprouts was of 1,14. The formation of callus in the base of the explants happened when cytokinins were added to the medium, and the roots formation happened in the absence of these and in the presence of the auxin, generating complete plants. Explants exposed to GA3 at 60 days of cultive showed a partial reversion, showing an increase in formed roots and average length of the sprouts. / O presente trabalho teve como objetivo o estudo da regeneração in vitro de cedro (Cedrela fissilis Vell.), uma árvore nativa de interesse econômico, pertencente à família Meliaceae. Para a desinfestação de sementes, foram testadas diferentes concentrações e tempos de imersão em hipoclorito de sódio e para a germinação, diferentes meios de cultura. Para o estabelecimento in vitro de segmentos nodais, foram adicionados ao meio de cultura WPM, reduzido a ¾ de sua concentração original, benlate (300 mg.l-1) e sulfato de estreptomicina (10 mg.l-1). Após, segmentos do nó cotiledonar advindos de plântulas germinadas in vitro com 30 dias de idade, foram utilizados para a multiplicação de brotações nos meios de cultura MS e WPM, em combinação ou não com 5μM.l-1 de BAP ou KIN . Foi testado também, a influência da citocinina BAP (0; 1,25; 2,5 e 5,0 μM.l-1) combinada ou não com as auxinas AIB ou ANA (0,5μM.l-1) em meio de cultura WPM durante dois subcultivos. Os segmentos do nó cotiledonar com 60 dias de cultivo em meio WPM e BAP (0; 1,25; 2,5 e 5,0 μM.l-1) foram transferidos para meio WPM adicionado apenas de GA3 a 3μM.l-1 permanecendo por mais 30 dias. Os resultados demonstram que as sementes desinfestadas com hipoclorito de sódio a 2% durante 10 minutos apresentaram a menor taxa de contaminação por fungos (8,7%) e a maior percentagem de germinação (80%), os meios MS e WPM proporcionaram percentagem de germinação de 72,5%. Os segmentos nodais de plantas de três anos de idade apresentaram uma taxa média de contaminação por bactérias de 13% após 21 dias de inoculação quando cultivados em meio de cultura WPM adicionado de benlate (300mg.l-1)mais sulfato de estreptomicina (10 mg.l-1)e taxa de sobrevivência de 83%. Os explantes provenientes da região do nó cotiledonar apresentaram regeneração média de brotações de 2,8 quando cultivados em meio WPM suplementado com BAP a 5μM.l-1, enquanto que, no meio MS, a taxa média de brotações foi de 2,5 por explante. Quanto testados em meio de cultura WPM, em diferentes concentrações de BAP, apenas aos 30 dias de cultivo, houve interação entre as doses da citocinina e a presença das auxinas AIB e ANA. O BAP a 5μM apresentou explantes com maiores taxas de multiplicação de brotações independente da adição das auxinas ao meio de cultura. Nos subcultivos subseqüentes, não houve interação entre as concentrações e o efeito da presença de auxina, em que o meio sem a presença desta, adicionado o BAP a 5μM, proporcionou a maior média de brotações por explante 2,29 (60 dias). O número médio de nós aos 30 dias de cultivo foi de 2,84 no meio contendo ANA mais 2,5 μM de BAP. Enquanto que, aos 60 dias, o meio de cultura sem auxina proporcionou uma média de 4,15 nós por explante, diferindo estatisticamente dos meios contendo auxina. Aos 90 dias de cultivo, o número de nós foi de 5,59 quando utilizado BAP a 5μM mais AIB ao meio de cultura. Quanto ao comprimento médio das brotações, o meio contendo ANA mostrou ser o mais eficiente (0,86 cm) aos 30 dias de cultivo. Aos 60 dias, o comprimento médio das brotações foi de 0,95 e, aos 90 dias o comprimento médio de brotações foi de 1,14. A formação de calos na base dos explantes ocorreu quando foi adicionada citocinina ao meio, e a formação de raízes ocorreu na ausência desta e na presença de auxina, gerando plantas completas. Explantes expostos ao GA3 aos 60 dias de cultivo mostraram parcial reversão, apresentando um aumento na percentagem de raízes formadas e comprimento médio de brotações.

Yes / Red Lustrous Wheelmade ware is one of the most recognisable classes of pottery from the Late Bronze Age of the east Mediterranean. Yet both its production source and the nature of its contents and use remain a source of some debate. These questions are tackled here through an intensive programme of scientific analysis involving 95 samples of Red Lustrous Wheelmade ware and related wares from seven sites in Turkey, Cyprus and Egypt. Petrography and instrumental neutron activation analysis are combined in the study of the ceramic fabrics, with a view to specifying the source of this ware; while gas chromatography and gas chromatography-mass spectrometry are used to analyse absorbed and visible residues in and on the sherd samples, in the hope of shedding light on vessel contents and possible use. The results of the fabric analysis show the ware to be extremely homogeneous, indicative of a single source: northern Cyprus is at present the most likely candidate, although further analysis, particularly of clay samples from the region in question, would certainly be desirable. The residue analysis suggests that Red Lustrous Wheelmade ware might have been used to carry some kind of plant oils, possibly perfumed, and that in some instances the vessel interior was coated with beeswax as a sealant. / AHRC

Ziele: Mittels absolutquantifizierender Protonen-Magnet-Resonanz-Spektroskopie (1H-MRS) wollten wir das Ergebnis einer Vorstudie bestätigen, die im Frontallappen einen reduzierten Quotienten von myo-Inositol/Gesamtcreatin (mI/tCr) bei Depressiven fand. Darüber hinaus testeten wir den antidepressiven Effekt von Inositol als Add-on-Therapie. Methodik: Wir untersuchten Einzelvoxel (2 x 2 x 2 cm3) in der weißen Substanz der rechten und linken Präfrontalregion mit Hilfe eines 3-Tesla Bruker Medspec Systems (STEAM Sequenz, TR/TE/TM = 6000/20/30 ms). Die einzelnen Metabolite wurden anhand des cerebralen Wassers als internem Standard quantifiziert (nach dem LCModell). Es wurden 24 unmedizierte Patienten mit unipolaren depressiven Episoden mit 24 alters- und geschlechtsgematchten gesunden Kontrollen verglichen. In doppelblindem, Plazebo-kontrollierten Parallelgruppen-Design erhielten die Patienten täglich 18 Gramm Inositol oder Plazebo zusätzlich zu Citalopram über vier Wochen. Ergebnisse: An der Baseline unterschieden sich die mI-, Cholin- und N-Acetyl-Aspartat-Konzentrationen der Patienten nicht von jenen der Kontrollen. Es fanden sich keine sich keine signifikanten Unterschiede zwischen Inositol- und Plazebo-Gruppe. Überraschenderweise zeigten die depressiven Patienten an der Baseline gegenüber den Kontrollen signifikant höhere tCr-Konzentrationen (mmol/kg) links (5,57 ± 0,96 vs. 4,87 ± 0,63; + 15 %, p < 0,01) und rechts präfrontal (5,29 ± 0,92 vs. 4,46 ± 0,41; + 17 %, p < 0,01). Nach der Behandlung ergab sich eine Reduktion der tCr-Konzentration links- (Tag 28: 5,05 ± 1,16; – 12 %, p = 0,08) und rechtsfrontal (Tag 28: 4,61 ± 1,07; – 9 %, p = 0,09). Die tCr-Konzentrationen der Patienten am Tag 28 unterschieden sich nicht mehr von jenen der Kontrollen. Zusammenfassung: Wir zeigten eine reversible Steigerung der tCr-Konzentration der Patienten im Vergleich zu Kontrollen, die auf Veränderungen des Creatin-Transports oder der ATP-Synthese bei unmedizierter unipolarer Depression hinweisen könnte. / Objectives: By means of proton magnetic resonance spectroscopy (1H-MRS) with absolute quantification we wanted to confirm our previous finding of decreased ratios of the metabolites myo-Inositol/total creatine (mI/tCr) in the right frontal brain of depressives. Moreover, we tested the antidepressive effect of oral Inositol ingestion as add-on-therapy. We measured concentrations (mmol/kg ww) of mI, tCr (= Creatine + Phosphocreatine), Choline (Cho) and N-Acetyl-Aspartate (NAA) in the frontal brain. Methods: Single voxels (2x2x2 cm3) in the white matter of the left and right prefrontal region were examined in a three Tesla Bruker Medspec System (STEAM sequence, TR/TE/TM = 6000/20/30 ms). Metabolites were quantified using the LCModel. At baseline, 24 drug-free patients with unipolar depressive episodes were compared to 24 age and sex matched healthy controls. In a double blind, placebo controlled parallel-group design patients received daily 18 grams Inositol or placebo as an add on therapy to Citalopram over four weeks. Results: At baseline, mI, Cho and NAA concentrations showed no significant differences between patients and controls. The treatment with Inositol did not result in any significant differences to the treatment with placebo. Surprisingly the patients showed significant higher tCr concentrations in the left (5.57 ± 0.96 vs. 4.87 ± 0.63; + 15 %, p < 0.01) as well as in the right prefrontal region (5.29 ± 0.92 vs. 4.46 ± 0.41; + 17 %, p < 0.01) compared to controls. The treatment caused a trend towards a decrease of tCr in the left (day 28: 5.05 ± 1.16; – 12 %, p = 0.08) and in the right frontal hemisphere (day 28: 4.61 ± 1.07; – 9 %, p = 0.09) compared to baseline. The differences between the patients’ tCr at day 28 and the tCr of controls were no more significant. Conclusion: We have found a state dependent increase of tCr concentration indicating bifrontal deviations in Creatine transport or ATP synthesis in drug free unipolar depressives.

in English The apoplastic barriers of the root (endodermis and exodermis) represent an important regulatory mechanism for the uptake of water and nutrients from the environment, ensuring its selectivity. In addition, both layers respond to stress factors by altering its rate and degree of cell wall modification, which affects the transport properties of the root and represents adaptive plants to high heterogeneity of the soil environment. Apoplastic barriers also respond to the availability of mineral nutrients. This issue has recently been intensively studied and a number of ambiguities persist. Interestingly, the deficiency of some mineral nutrients stimulates the differentiation of barriers, while the deficiency of other mineral nutrients delays the differentiation. In addition, different plant species react differently to the deficiency of the same element. Another interesting aspect is the fact that the reaction of the endodermis and exodermis is localized and takes place mainly in that part of the root system which is directly exposed to the stress factor. This phenomenon has been observed with cadmium toxicity, but more recently with local nutrient deficiencies (nitrogen and potassium) in Zea mays. This diploma thesis deals with the functional significance of localized enhancing or delaying...

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