Mineral uptake in tobacco leaf discs during different developmental stages of shoot organogenesis

Relationships between mineral uptake and tobacco shoot organogenesis were investigated during three morphogenic phases: phase 1, days 0-10, pre-meristem formation; phase 2, days 10-20, meristem initiation and formation; and phase 3, days 20-35, growth and differentiation of induced meristems into leafy shoots. The mineral content of both shoot-forming (SF) and non-shoot-forming (NSF) media was examined over the 35-day culture period. Both SF and NSF explants rapidly consumed iron during phase 1. Nitrate uptake in SF explants was high and independent of explant growth during phases 1 and 2, but greatest and strongly correlated with growth during phase 3. Phosphorus uptake was highest in SF explants during phases 2 and 3, and correlated with explant growth. Uptake of potassium, calcium and sulphur was strongly associated with explant growth during phase 3 whereas magnesium uptake was only poorly correlated with growth. Results from this study indicate that particular minerals may have an important role in regulating development as well as generally supporting growth.

Electron exchange coupling for single-donor solid-state spin qubits

Intervalley interference between degenerate conduction band minima has been shown to lead to oscillations in the exchange energy between neighboring phosphorus donor electron states in silicon [B. Koiller, X. Hu, and S. Das Sarma, Phys. Rev. Lett. 88, 027903 (2002); Phys. Rev. B 66, 115201 (2002)]. These same effects lead to an extreme sensitivity of the exchange energy on the relative orientation of the donor atoms, an issue of crucial importance in the construction of silicon-based spin quantum computers. In this article we calculate the donor electron exchange coupling as a function of donor position incorporating the full Bloch structure of the Kohn-Luttinger electron wave functions. It is found that due to the rapidly oscillating nature of the terms they produce, the periodic part of the Bloch functions can be safely ignored in the Heitler-London integrals as was done by Koiller, Hu, and Das Sarma, significantly reducing the complexity of calculations. We address issues of fabrication and calculate the expected exchange coupling between neighboring donors that have been implanted into the silicon substrate using an 15 keV ion beam in the so-called top down fabrication scheme for a Kane solid-state quantum computer. In addition, we calculate the exchange coupling as a function of the voltage bias on control gates used to manipulate the electron wave functions and implement quantum logic operations in the Kane proposal, and find that these gate biases can be used to both increase and decrease the magnitude of the exchange coupling between neighboring donor electrons. The zero-bias results reconfirm those previously obtained by Koiller, Hu, and Das Sarma.

Effect of Co addition on the lattice parameter, electrical conductivity and sintering of gadolinia-doped ceria

Co-sintering aid has been added to Ce1.9Gd0.1O1.95 (CGO) by treating a commercial powder with Co(NO3)(2) (COCGO), X-ray diffraction (XRD) measurements of lattice parameter indicated that the Co was located on the CGO particle surface after calcination at 650 degreesC. After heat treatment at temperatures above 650 degreesC, the room temperature lattice parameter of CGO was found to increase, indicating redistribution of the Gd. Compared to CGO, the lattice parameter of CGO + 2 cation% Co (2CoCGO) was lower for a given temperature (650-1100 degreesC), A.C. impedance revealed that the lattice conductivity of 2CoCGO was enhanced when densified at lower temperatures, Transmission electron microscopy (TEM) showed that, even after sintering for 4 h at 980 degreesC, most of the Co was located at grain boundaries. (C) 2002 Published by Elsevier Science B.V.

Full-scale demonstration of biological nutrient removal in a single tank SBR process

Complete biological nutrient removal (BNR) in a single tank, sequencing batch reactor (SBR) process, is demonstrated here at full-scale on a typical domestic wastewater. The unique feature of the UniFed process is the introduction of the influent into the settled sludge blanket during the settling and decant periods of the SBR operation. This achieves suitable conditions for denitrification and anaerobic phosphate release which is critical to successful biological phosphorus removal, It also achieves a selector effect, which helps in generating a compact, well settling biomass in the reactor. The results of this demonstration show that it is possible to achieve well over 90% removal of GOD, nitrogen and phosphorus in such a process. Effluent quality achieved over a six-month operating period directly after commissioning was: 29 mg/l GOD, 0.5 mg/l NH4-N, 1.5 mg/l NOx-N and 1.5 mg/l PO4-P (50%-iles of daily samples). During an 8-day, intensive sampling period, the effluent BOD5 was

Identification and comparison of aerobic and denitrifying polyphosphate-accumulating organisms

Two laboratory-scale sequencing batch reactors (SBRs) were operated for enhanced biological phosphorus removal (EBPR) in alternating anaerobic-aerobic or alternating anaerobic-anoxic modes, respectively. Polyphosphate-accumulating organisms (PAOs) were enriched in the anaerobic-aerobic SBR and denitrifying PAOs (DPAOs) were enriched in the anaerobic-aerobic SBR. Fluorescence in situ hybridization (FISH) demonstrated that the well-known PAO, Candidatus Accumulibacter phosphatis was abundant in both SBRs, and post-FISH chemical staining with 4,6-diamidino-2-phenylindol (DAPI) confirmed that they accumulated polyphosphate. When the anaerobic-anoxic SBR enriched for DPAOs was converted to anaerobic-aerobic operation, aerobic uptake of phosphorus by the resident microbial community occurred immediately. However, when the anaerobic-aerobic SBR enriched for PAOs was exposed to one cycle with anoxic rather than aerobic conditions, a 5-h lag period elapsed before phosphorus uptake proceeded. This anoxic phosphorus-uptake lag phase was not observed in the subsequent anaerobic-aerobic cycle. These results demonstrate that the PAOs that dominated the anaerobic-aerobic SBR biomass were the same organisms as the DPAOs enriched under anaerobic-anoxic conditions. (C) 2003 Wiley Periodicals, Inc.

Model-based analysis of anaerobic acetate uptake by a mixed culture of polyphosphate-accumulating and glycogen-accumulating organisms

An increasing number of studies shows that the glycogen-accumulating organisms (GAOs) can survive and may indeed proliferate under the alternating anaerobic/aerobic conditions found in EBPR systems, thus forming a strong competitor of the polyphosphate-accumulating organisms (PAOs). Understanding their behaviors in a mixed PAO and GAO culture under various operational conditions is essential for developing operating strategies that disadvantage the growth of this group of unwanted organisms. A model-based data analysis method is developed in this paper for the study of the anaerobic PAO and GAO activities in a mixed PAO and GAO culture. The method primarily makes use of the hydrogen ion production rate and the carbon dioxide transfer rate resulting from the acetate uptake processes by PAOs and GAOs, measured with a recently developed titration and off-gas analysis (TOGA) sensor. The method is demonstrated using the data from a laboratory-scale sequencing batch reactor (SBR) operated under alternating anaerobic and aerobic conditions. The data analysis using the proposed method strongly indicates a coexistence of PAOs and GAOs in the system, which was independently confirmed by fluorescent in situ hybridization (FISH) measurement. The model-based analysis also allowed the identification of the respective acetate uptake rates by PAOs and GAOs, along with a number of kinetic and stoichiometric parameters involved in the PAO and GAO models. The excellent fit between the model predictions and the experimental data not involved in parameter identification shows that the parameter values found are reliable and accurate. It also demonstrates that the current anaerobic PAO and GAO models are able to accurately characterize the PAO/GAO mixed culture obtained in this study. This is of major importance as no pure culture of either PAOs or GAOs has been reported to date, and hence the current PAO and GAO models were developed for the interpretation of experimental results of mixed cultures. The proposed method is readily applicable for detailed investigations of the competition between PAOs and GAOs in enriched cultures. However, the fermentation of organic substrates carried out by ordinary heterotrophs needs to be accounted for when the method is applied to the study of PAO and GAO competition in full-scale sludges. (C) 2003 Wiley Periodicals, Inc.

Metabolic model for glycogen-accumulating organisms in anaerobic/aerobic activated sludge systems

Glycogen-accumulating organisms (GAO) have the potential to directly compete with polyphosphate-accumulating organisms (PAO) in EBPR systems as both are able to take up VFA anaerobically and grow on the intracellular storage products aerobically. Under anaerobic conditions GAO hydrolyse glycogen to gain energy and reducing equivalents to take up VFA and to synthesise polyhydroxyalkanoate (PHA). In the subsequent aerobic stage, PHA is being oxidised to gain energy for glycogen replenishment (from PHA) and for cell growth. This article describes a complete anaerobic and aerobic model for GAO based on the understanding of their metabolic pathways. The anaerobic model has been developed and reported previously, while the aerobic metabolic model was developed in this study. It is based on the assumption that acetyl-CoA and propionyl-CoA go through the catabolic and anabolic processes independently. Experimental validation shows that the integrated model can predict the anaerobic and aerobic results very well. It was found in this study that at pH 7 the maximum acetate uptake rate of GAO was slower than that reported for PAO in the anaerobic stage. On the other hand, the net biomass production per C-mol acetate added is about 9% higher for GAO than for PAO. This would indicate that PAO and GAO each have certain competitive advantages during different parts of the anaerobic/aerobic process cycle. (C) 2002 Wiley Periodicals, Inc.

Assessing forest fire as a potential PCDD/F source in Queensland, Australia

Forest fires are suggested as a potential and significant source of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs), even though no studies to date provide sufficient evidence to confirm forest fires as a source of PCDD/Fs. Recent investigations in Gueensland, Australia have identified a widespread contamination of PCDDs (in particular OND) in soils and sediments in the coastal region from an unknown source of PCDD/Fs. Queensland is predominately rural; it has few known anthropogenic sources of PCDD/Fs, whereas forest fires are a frequent occurrence. This study was conducted to assess forest fires as a potential source of the unknown PCDD/F contamination in Queensland. A combustion experiment was designed to assess the overall mass of PCDD/Fs before and after a simulated forest fire. The results from this study did not identify an increase in Sigma-PCDD/Fs or OCDD after the combustion process. However, specific non-2,3,7,8 substituted lower chlorinated PCDD/Fs were elevated after the combustion process, suggesting formation from a precursor. The results from this study indicate that forest fires are unlikely to be the source of the unknown PCDD contamination in Gueensland, rather they are a key mechanism for the redistribution of PCDD/Fs from existing sources and precursors.

Compositional changes of Australia-grown Western Schley pecans [Carya illinoinensis (Wangenh.) K. Koch] during maturation

Changes in composition during the maturation of Western Schley pecans [Carya illinoinensis (Wangenh.) K. Koch] grown in Australia were investigated. Pecans of different maturity levels were collected at monthly intervals between March and June in. 1999 and 2000 and analyzed for the concentrations of moisture, total lipid, sucrose, raffinose, protein, and the minerals aluminum, boron, calcium, copper, iron, potassium, magnesium, manganese, sodium, phosphorus, sulfur, and zinc. Moisture, total lipid, and calcium contents changed significantly (p < 0.05) with harvest time and maturity, whereas the other components did not. Western Schley pecans grown in Australia should be harvested after the shuck has opened and it is either green or brown in color to maximize total lipid content and quality. This occurred after May 11 in 1999 and after May 17 in 2000.

Variabilidade espacial e temporal de atributos químicos do solo em povoamento de eucalipto

Nos anos mais recentes, observa-se aumento na adoção das técnicas de silvicultura de precisão em florestas plantadas no Brasil. Os plantios de eucalipto ocorrem preferencialmente em áreas com baixa fertilidade de solo e consequentemente baixa produtividade. Logo, para otimizar ao máximo a produção, é necessário saber o quanto essa cultura pode produzir em cada local (sítio). Objetivou-se aplicar uma metodologia que utiliza técnicas de estatística, geoestatística e geoprocessamento, no mapeamento da variabilidade espacial e temporal de atributos químicos do solo cultivado com eucalipto, em área de 10,09 ha, situada no sul do estado do Espírito Santo. Os atributos químicos da fertilidade do solo estudados foram: fósforo (P), potássio (K), cálcio (Ca) e magnésio (Mg), no ano da implantação do povoamento do eucalipto, em 2008, e três anos após, em 2011. O solo foi amostrado em duas profundidades, 0-0,2 m e 0,2-0,4 m, nos 94 pontos de uma malha regular, com extensão de 33 x 33 m. Os dados foram analisados pela estatística descritiva e, em seguida, pela geoestatística, por meio do ajuste de semivariogramas. Diferentes métodos de interpolação foram testados para produzir mapas temáticos mais precisos e facilitar as operações algébricas utilizadas. Com o auxílio de índices quantitativos, realizou-se uma análise geral da fertilidade do solo, por meio da álgebra de mapas. A metodologia utilizada neste estudo possibilitou mapear a variabilidade espacial e temporal de atributos químicos do solo. A análise variográfica mostrou que todos os atributos estudados apresentaram-se estruturados espacialmente, exceto para o atributo P, no Ano Zero (camada 0-0,2 m) e no Ano Três (ambas as camadas). Os melhores métodos de interpolação para o mapeamento de cada atributo químico do solo foram identificados com a ajuda gráfica do Diagrama de Taylor. Mereceram destaque, os modelos esférico e exponencial nas interpolações para a maioria dos atributos químicos do solo avaliados. Apesar de a variação espacial e temporal dos atributos estudados apresentar-se, em média, com pequena variação negativa, a metodologia usada mostrou variações positivas na fertilidade do solo em várias partes da área de estudo. Além disso, os resultados demonstram que os efeitos observados são majoritariamente em função da cultura, uma vez que não foram coletadas amostras de solo em locais adubados. A produtividade do sítio florestal apresentou-se com tendências semelhantes às variações ocorridas na fertilidade do solo, exceto para o magnésio, que se mostrou com tendências espaciais para suporte de elevadas produtividades, de até 50 m3 ha-1 ano-1. Além de mostrar claramente as tendências observadas para as variações na fertilidade do solo, a metodologia utilizada confirma um caminho operacional acessível para empresas e produtores florestais para o manejo nutricional em florestas plantadas. O uso dos mapas facilita a mobilização de recursos para melhorar a aplicação de fertilizantes e corretivos necessários.

Initial performance of pineapple and utilization of rock phosphate applied in combination with organic compounds to leaf axils

Rock phosphates have low solubility in water, but good solubility in acid. The use of organic compounds together with these phosphorus sources applied to the basal leaf axils of pineapple can increase the solubility of this phosfate source and increase the P availability to the crop. A greenhouse experiment was conducted using Araxá rock phosphate (10 g) in combination or not with solutions containing increasing concentrations of humic acids (0 to 40 mmol L-1 of carbon), with or without citric acid (0.005 mmol L-1), applied to basal leaf axils of pineapple cv. Pérola. Growth and nutritional characteristics of aerial plant parts were assessed. Growth rates of aerial parts and N, P, K, Ca and Mg contents increased curvilinearly with increasing concentration of carbon in the form of humic acids. Maximum values were found for the concentration of 9.3 mmol L-1 of carbon combined with 0.005 mmol L-1 of citric acid and natural phosphate.

Initial growth of maize in response to application of rock phosphate, vermicompost and endophytic bacteria

Due to the high energy requirement and demand for non-renewable resources for the production of chemical fertilizers, added also to the environmental impact caused by the use of such products, it is important to intensify research on bio-based agricultural inputs. The use of nitrogen-fixing endophytic and phosphate solubilizing bacteria can provide these nutrients to the plants from the air and poorly soluble phosphorus sources, such as phosphate rock. The objective of this study was to evaluate the nutrition and initial growth of maize (Zea mays L.) in response to the inoculation of nitrogen-fixing and rock phosphate solubilizing endophytic bacteria, in single or mixed formulation, applied with vermicompost. The treatments containing bacteria, both diazotrophic and phosphate solubilizing, when compared to controls, showed higher levels of leaf nitrogen and phosphorus in maize, as well as higher growth characteristics. The application of vermicompost showed synergistic effect when combined with endophytic bacteria. Thus, the innovation of the combination of the studied factors may contribute to the early development of maize.

Growth and nutrient uptake of coffee seedlings cultivated in nutrient solution with and without silicon addition

In recent years, the application of silicon (Si) in crops, including coffee, has become a common practice. The objective of this study was to assess the silicon uptake by coffee seedlings and its effects on plant growth, water and macro and micronutrient uptake. The research was conducted using nutrient solution in a greenhouse at the Departamento de Fitotecnia da Universidade Federal de Viçosa, in a completely randomized design with two treatments (with and without silicon) and three replications. Each plot consisted of three plants grown in a 800 mL vessel containing the treatment solutions. At every three days, water consumption, the concentration of OH - and the depletion of Si and K were assessed in the nutrient solutions. After 33 days, the plants were assessed with regard to their fresh and dry weight of leaves, roots and stem, shoot height and total length of the plant (shoot and root). Number of leaves and internodes, and the content and accumulation of silicon, macro, and micronutrients were also determined. The consumption of water, the amount of potassium uptake and, biomass accumulation were greater in plants grown in solution without silicon addition. However, the concentration of OH- in the solution and the amount of silicon uptake were greater in plants grown in solution with added silicon. Silicon accumulation was greater in leaves than in stem and roots. Silicon decreased coffee plant accumulation of phosphorus, potassium, calcium, zinc, copper and iron.

No-till corn performance in response to P and fertilization modes

No-tillage systems provide soil changes that affect nutrient dynamics, hence, changing rates and forms of fertilizer application. This study aimed to evaluate the effect of phosphorus (P) and modes of nitrogen (N) and P application in corn under long-term no-tillage in a clayey Oxisol. Two experiments were carried out in the same experimental area and in the same year, in a randomized blocks design with four replications. In experiment I, the treatments consisted of five doses of phosphorus (0, 40, 80, 120 and 160 kg ha-1 of P2O5) applied in the sowing furrow. In experiment II, the treatments consisted of the N and P application modes (topdressing, in the sowing furrow and control - without N and P). Experiment I evaluated the root length, P uptake and grain yield and, the Experiment II, the firing height and yield. The P rates provided linear increases in root length in the 0-10 cm layer, P uptake and grain production. The different modes of application provided differences in the firing height and corn yield. The control treatment (0 kg ha-1 of N and P) provided the highest firing height, superior than those of topdressing and application in the furrow, which were not significantly different. The topdress application of N and P provided an increase in corn yield that exceeded 16 and 42% of the application in the furrow and the control, respectively. Thus, the results confirmed that increasing rates of P2O5, in soil with high initial P content, influence positively corn production factors, but with little significant responses, and the topdress application of N and P on soil with high P content, without water restriction, provided increased grain yield in relation to the application in the furrow.

Chemical, morphological, rheological and thermal properties of Solanum lycocarpum phosphorylated starches

The increasing need for starches with specific characteristics makes it important to study unconventional starches and their modifications in order to meet consumer demands. The aim of this work was to study physicochemical characteristics of native starch and phosphate starch of S. lycocarpum. Native starch was phosphated with sodium tripolyphosphate (5-11%) added with stirring. Chemical composition, morphology, density, binding ability to cold water, swelling power and solubility index, turbidity and syneresis, rheological and calorimetric properties were determined. Phosphorus was not detected in the native sample, but the phosphating process produced modified starches with phosphorus contents of 0.015, 0.092 and 0.397%, with the capacity of absorbing more water, either cold or hot. Rheological data showed the strong influence of phosphorus content on viscosity of phosphate starch, with lower pasting temperature and peak viscosity higher than those of native starch. Enthalpy was negatively correlated with the phosphorus content, requiring 9.7; 8.5; 8.1 and 6.4 kJ g-1 of energy for the transition from the amorphous to the crystalline state for the starch granules with phosphorus contents of 0; 0.015; 0.092 and 0.397%, respectively. Cluster analysis and principal component analysis showed that starches with 0.015 and 0.092% phosphorus have similar characteristics and are different from the others. Our results show that the characteristics of phosphate modified S. lycocarpum starch have optimal conditions to meet the demands of raw materials, which require greater consistency in stickiness, combined with low rates of retrogradation and syneresis.