A cebola comum Allium cepa L. (2n=16), devido à sua excelente condição cromossômica, tem sido largamente utilizada como um sistema de testes para se examinar os efeitos citogenéticos causados por diversos compostos químicos em material biológico. Em estudos de monitoramento de riscos ambientas, observou-se limitação no crescimento das raízes quando as cebolas são expostas a aguas residuárias provenientes de indústrias químicas. Nesse estudo, nós avaliamos este sistema de testes escolhendo alguns compostos de metais pesados, cujos efeitos em outros sistemas de testes já se encontram descritos. Além disso, foram estuados vários fatores que poderiam interferir nos resultados tais como: temperatura; luminosidade; qualidade da água e qualidade das cebolas. As concentrações mais baixas empregadas (1,5 mg/l) nos testes, de cádmio e cobre demostraram alta capacidade inibidora sobre o crescimento das raízes. O zinco apresentou toxicidade moderada a 1,5 mg/l e crescente às concentrações sucessivas mais elevadas. Efluentes industriais, contendo misturas de níquel e sulfatos ou cobre e cianeto, demonstraram-se altamente inibidores às concentrações mais baixas empregadas (0,7%), resultados que demonstram a alta sensibilidade do teste aos sais de metais pesados. Quanto às condições experimentais que levaram a esses resultados, os testes revelaram que não existe influência pronunciada dos fatores luminosidade e temperatura. Quanto à água para controle e diluição, não deve ser de torneira devido ao efeito inibidor do zinco e do cobre. Os resultados foram contraditórios em relação a um possível efeito osmótico da água destilada, sendo conveniente adicionar entre 100 a 250 mg/l de NaCl. A melhor resposta foi obtida com cebolas de origem argentina de 3,5 a 4,0 cm de diâmetro sendo preferível a manutenção de cascas para evitar murchamento. / The common onion Allium cepa. L., due to its excellent chromosome conditions, has been widely used as a test system for examining the citogenetic effects of several chemical compounds on biological material. It has been observerd, in monitoring environmental studies, some growth restriction on Allium roots when they are exposed to wastewater from chemical factories. In this study, we evaluate these test systems by choosing some hard metals which harmful effects on biological materials has been already described. Furthermore, some factors that could interfere on the results, such as: temperature; light; water quality and onion quality were studied. The lowest concentration (1.5 mg/l) for cadmium and cupper were found to have hard capacity to inhibit root growth. The zinc showed moderate toxicity at 1.5 mg/l and this effect was more evident at increased concentrations. The industrial wastewater that contains mixture of nickel and sulphate or cupper and cyanate inhibited root growth at lower concentration (0.7%). These results showed that the test system has high sensitivity for hard metals. There was no direct influence of temperature and light on the experiment conditions. With regard to the type of water, tap water should not be used because of inhibition on the root growth caused by zinc and copper. The results contradicted a potential osmotic effect of distillated water, being convenient to add 100 - 250 mg/l of NaCl. The best response was obtained with onions from Argentina with 3.5 - 4.0 cm of diameter being recommended to keep the onion peel for avoiding dryness.

A abertura econômica (1990) e a consolidação do tratado do Mercosul (1995) provocaram mudanças nas estruturas de produção e comercialização da cebola no Brasil na década de 90. A principal mudança observada foi com a integração comercial entre Brasil e Argentina, quando o mercado brasileiro (que era auto-suficiente) passou a ter maior participação da cebola do país vizinho e os agentes do mercado passaram a diferenciar produto estrangeiro em relação ao doméstico. Assim, o presente trabalho procurou estimar funções de oferta e demanda do bulbo importado para o Brasil. Para análise foram desenvolvidos um modelo teórico e um modelo gráfico, que auxiliaram na especificação do modelo econométrico para o produto em estudo. O modelo foi ajustado por equações simultâneas utilizando o método de Mínimos Quadrados de Dois Estágios. Os coeficientes encontrados apresentaram sinais coerentes com o modelo econômico teórico definido. Os resultados obtidos permitiram interpretar a dinâmica do mercado importador de cebola argentina. Ficou claro que há um efeito importante do preço (e, portanto, da disponibilidade) de cebola nacional sobre o preço que será pago à cebola argentina. Os argentinos comportam-se como tomadores de preços e são altamente sensíveis ao comportamento do mercado brasileiro. O volume exportado pelos argentinos responde expressivamente ao preço pago no Brasil e à taxa de câmbio da moeda brasileira. O Mercosul gerou uma efetiva integração do mercado da cebola entre Brasil e Argentina, a qual trouxe conseqüências para a produção e o consumo em ambos. / The economic market opening (1990) and the consolidation of the Mercosul agreement (1995) promoted changes in the framework of production and marketing of onion in Brazil in the 1990’s. The main change noticed was the market integration between Brazil and Argentina, when the Brazilian market - which was self-sufficient then - started to have more participation in the market of the neighbor country and the market agents started to differ foreign from domestic products. Thus, this current study aimed to estimate the supply and demand for the bulb imported to Brazil. For the analysis, a theoretical and a graphic model were developed, which helped specify the econometric model for the product of study. The model was adjusted by the simultaneous equations of Minimum Square of Two Stages. The coefficients found showed coherent signs to the defined economic theoretical model. The results obtained allowed to interpret the dynamic of the Argentine onion importing market. It was clear that there is an important effect of price (and, therefore, of the availability) of domestic onion to the price which will be paid for the Argentine onion. The Argentine behaves as price takers and are highly sensitive to the Brazilian market behavior. The amount exported by the Argentina are affected expressively the prices practiced in Brazil and by the exchange rate of the Brazilian currency. The Mercosul generated an effective integration between Brazil and Argentina, which has brought consequences to the production and consumption in both countries.

A cebola (Allium cepa L.) é uma das culturas hortícolas de maior importância no Brasil, com cerca de 70.000 ha e produção de 912.000 t. O mercado apresenta entressafra de fevereiro a julho; sendo o cultivo de verão, uma forma de aumentar os lucros. Uma das dificuldades deste cultivo é a produção de mudas para o transplante. Com o objetivo de verificar o comportamento na fase de muda do híbrido de dias curtos Mercedes, sob cultivo protegido como cultura de verão, o experimento foi instalado em estufa, no Campo Experimental do Departamento de Produção Vegetal, da Escola Superior de Agricultura 'Luiz de Queiroz'. O experimento constou da produção de mudas em ambiente protegido, utilizando bandejas de isopor de 288 células. Os fatores testados foram quatro tipos de substratos (Plantmax HT e três formulações experimentais: Plantmax HT com PG Mix, Teste CM e Teste CM com PG Mix) e dois números de mudas por células (3 e 4 mudas). A subparcela testada foi a suplementação mineral com nitrogênio (1,5 g/l de água de nitrato de cálcio + 1,0 g/l de água de nitrato de potássio; 2 e 3 vezes por semana). Cada bandeja foi considerada uma parcela, sendo dividida em duas subparcelas em função da suplementação mineral com nitrogênio. Em cada subparcela foram semeadas 70 células, sendo que foram deixadas 4 fileiras livres de substratos para separação das subparcelas. Foram utilizadas 24 bandejas. O delineamento experimental adotado foi o inteiramente casualizado, com fatorial 4 X 2 em parcelas subdivididas, e com 3 repetições. A semeadura foi realizada 05/02/99, com a germinação ocorrendo 6 dias depois. Foi realizado um desbaste para ajuste de estande 7 dias após a emergência (DAE) e a suplementação mineral começou 11 DAE. Foram realizadas três avaliações das mudas aos 16, 21 e 26 DAE. Os parâmetros avaliados foram: diâmetro do pseudocaule, altura da planta, peso da matéria seca da parte aérea, peso da matéria seca do sistema radicular. Com base nos resultados encontrados no presente trabalho, podemos concluir que a densidade de 3 mudas por célula apresentou menor taxa de bulbificação precoce e maior altura da planta; os substratos Plantmax HT e Plantmax com o PG Mix apresentaram maior peso seco do sistema radicular e que a aplicação da suplementação mineral com nitrogênio, realizada 3 vezes por semana apresentou os maiores valores com relação aos parâmetros altura da planta e peso da matéria seca da parte aérea, não apresentando bulbificação precoce das mudas. / Onion (Allium cepa L.) is one of the more important cultivated vegetables in Brazil, where this crop is being cultivated in approximately 70.000 hectares annually. The total production of onion in the country was of 912.000 tons last year. Summer-planted onion is a way of increasing the growers's profits. Farmers are searching for an more manageable alternative procedure for seedlings's production. Local greenhouses may be a good place for the production of onion transplants, but, as far as we know, no information concerning onion production in cells, on greenhouse, is available up to the moment. The experiment was carried out in a greenhouse from the Vegetable Production Department on the Escola Superior de Agricultura 'Luiz de Queiroz' - Universidade de São Paulo, with the objective of studying the behavior of the shortdays-hybrid Mercedes in its initial stage of plant raising, under controlled environment as summer-planted onions. The experiment consisted on the production of plants in controlled environment, using 288-cell styrofoam trays. There were four studied factors, namely, different substrates (Plantmax HT and three experimental formulations: Plantmax HT with PG Mix, Test CM and Test CM with PG Mix) and two different numbers of plants per cells (3 and 4 plants). The sub plot was the N application - 1,5 g. calcium nitrate of calcium/1l water + 1,0 g potassium nitrate /ll water (2 and 3 times a week). 24 trays were used in the experiment. Each tray was a plot, divided in two sub plots. 70 cells were sowed in each sub plot. 4 lines without substrate separated the sub plots. The treatments were designed in split-plot pattern with three replications each, with the substrate and the number of plants per cells as main plots and N application as the sub-plot. Sowing was performed on 99/Feb./05, and the emergency began 6 days later . The seedlings were thinned so that, seven days after the emergency (DAE), only 3 to 4 plants per cells would remain. N appication started 11 DAE. Three evaluations of the seedlings were accomplished to the 16, 21 and 26 DAE. The appraised parameters were: diameter of the pseudostem, height of the plant, weight of the dry matter of the aerial part, weight of the dry matter of the root system. This experiment's data indicate that the number of 3 plants per cells decrease the earlier onset of bulbing and increase the height of the plant; the Plantmax HT and Plantmax with PG Mix substrates increase the roots's dry weight; and the N application, 3 times a week, increase the values of height of the plant and leaves's dry weight, and does not result in earlier onset of bulbing.

A cebola comum Allium cepa L. (2n=16), devido à sua excelente condição cromossômica, tem sido largamente utilizada como um sistema de testes para se examinar os efeitos citogenéticos causados por diversos compostos químicos em material biológico. Em estudos de monitoramento de riscos ambientas, observou-se limitação no crescimento das raízes quando as cebolas são expostas a aguas residuárias provenientes de indústrias químicas. Nesse estudo, nós avaliamos este sistema de testes escolhendo alguns compostos de metais pesados, cujos efeitos em outros sistemas de testes já se encontram descritos. Além disso, foram estuados vários fatores que poderiam interferir nos resultados tais como: temperatura; luminosidade; qualidade da água e qualidade das cebolas. As concentrações mais baixas empregadas (1,5 mg/l) nos testes, de cádmio e cobre demostraram alta capacidade inibidora sobre o crescimento das raízes. O zinco apresentou toxicidade moderada a 1,5 mg/l e crescente às concentrações sucessivas mais elevadas. Efluentes industriais, contendo misturas de níquel e sulfatos ou cobre e cianeto, demonstraram-se altamente inibidores às concentrações mais baixas empregadas (0,7%), resultados que demonstram a alta sensibilidade do teste aos sais de metais pesados. Quanto às condições experimentais que levaram a esses resultados, os testes revelaram que não existe influência pronunciada dos fatores luminosidade e temperatura. Quanto à água para controle e diluição, não deve ser de torneira devido ao efeito inibidor do zinco e do cobre. Os resultados foram contraditórios em relação a um possível efeito osmótico da água destilada, sendo conveniente adicionar entre 100 a 250 mg/l de NaCl. A melhor resposta foi obtida com cebolas de origem argentina de 3,5 a 4,0 cm de diâmetro sendo preferível a manutenção de cascas para evitar murchamento. / The common onion Allium cepa. L., due to its excellent chromosome conditions, has been widely used as a test system for examining the citogenetic effects of several chemical compounds on biological material. It has been observerd, in monitoring environmental studies, some growth restriction on Allium roots when they are exposed to wastewater from chemical factories. In this study, we evaluate these test systems by choosing some hard metals which harmful effects on biological materials has been already described. Furthermore, some factors that could interfere on the results, such as: temperature; light; water quality and onion quality were studied. The lowest concentration (1.5 mg/l) for cadmium and cupper were found to have hard capacity to inhibit root growth. The zinc showed moderate toxicity at 1.5 mg/l and this effect was more evident at increased concentrations. The industrial wastewater that contains mixture of nickel and sulphate or cupper and cyanate inhibited root growth at lower concentration (0.7%). These results showed that the test system has high sensitivity for hard metals. There was no direct influence of temperature and light on the experiment conditions. With regard to the type of water, tap water should not be used because of inhibition on the root growth caused by zinc and copper. The results contradicted a potential osmotic effect of distillated water, being convenient to add 100 - 250 mg/l of NaCl. The best response was obtained with onions from Argentina with 3.5 - 4.0 cm of diameter being recommended to keep the onion peel for avoiding dryness.

Electrocatalysis is key to both sensitive electrochemical sensing and efficient electrochemical energy conversion. Despite high catalytic activity, traditional metal catalysts have poor stability, low selectivity, and high cost. Metal-free, carbon-based materials are emerging as alternatives to metal-based catalysts because of their attractive features including natural abundance, environmental friendliness, high electrical conductivity, and large surface area. Altering surface functionalities and heteroatom doping are effective ways to promote catalytic performance of carbon-based catalysts. The first chapter of this dissertation focuses on developing electrode modification methods for electrochemical sensing of biomolecules. After electrochemical pretreatment, glassy carbon demonstrates impressive figures-of-merit in detecting small, redox-active biomolecules such as DNA bases and neurotransmitters. The results highlight a simplified surface modification procedure for producing efficient and highly selective electrocatalysts. The next four chapters focus on evaluating nitrogen-doped carbon nano-onions (𝑛-CNOs) as electrocatalysts for oxygen reduction and CO2 reduction. 𝑛-CNOs exhibit excellent electrocatalytic performance toward O2 to H2O reduction, which is a pivotal process in fuel cells. 𝑛-CNOs demonstrate excellent resistance against CO poisoning and long-term stability compared to state-of-the-art Pt/C catalysts. In CO2 electrochemical conversion, 𝑛-CNOs demonstrate significant improvement in catalytic performance toward reduction of CO2 to CO with a low overpotential and high selectivity. The outstanding catalytic performance of 𝑛-CNOs originates from the asymmetric charge distribution and creation of catalytic sites during incorporation of nitrogen atoms. High contents of pyridinic and graphitic N are critical for high catalytic performance. This work suggests that carbon-based materials can be outstanding alternatives to traditional metal-based electrocatalysts when their microstructures and surface chemistries are properly tailored.

Onion thrips (Thrips tabaci) and Iris Yellow Spot Virus (IYSV) constitute a pest complex of global concern for allium growers. Yield losses due to onion thrips alone can be heavy, and in tandem with IYSV, these losses can be complete. This study was one phase of a multi-phase research project intent on exploring the potential drivers of thrips and virus infestation in onion. Preliminary observations in participating growers’ fields in northern Utah pointed towards a potential link between weedy field borders and thrips/IYSV infestation in onion. Field work was carried out at the Kaysville experiment station examining the possible relationships between thrips and IYSV incidence in onion and the presence of adjacent weed populations. This research was conducted with the intent of guiding growers’ decisions regarding field border management, and to provide additional insights into onion thrips behavior. While implications for growers remain unclear, thrips preferences regarding host plant utilization were identified, as well as preliminary evidence of additional plant species capable of hosting IYSV.

People experience the irritating tearing and burning sensation of lachrymatory factor (LF, propanthial S-oxide) when cutting or chopping onion bulbs. LF is produced by lachrymatory factor synthase (LFS) specifically from 1-propenyl sulfenic acid, a breakdown product of trans-1-propenyl-L-cysteine sulfoxide (1-PRENCSO) by alliinase. This thesis describes strategies to produce a tearless onion by using RNA interference (RNAi) silencing. To determine whether a gene silencing cassette can silence lfs gene transcripts from onion (Allium cepa L.), a crop recalcitrant to genetic transformation, a gene silencing assessment system was developed by using a model plant as a host for the gene of interest. Tobacco (Nicotiana tabacum) plants transgenic for LFS enzyme activity from onion were first produced by introducing a CaMV 35S-onion-lfs gene construct. These plants were then subjected to a second transformation with an RNAi construct directed against the lfs gene sequence. LFS enzyme activity assay showed that the transgenic plants, containing both the lfs gene and the RNAi construct, had significantly reduced LFS activity. This observation was supported by Western analysis for the LFS protein and further validated by quantitative RT-PCR analysis that demonstrated a significant reduction in the lfs transcript level in the dual transformants. This work demonstrated that the RNAi construct is a suitable candidate for the development of a tearless onion. This model plant RNAi system has wide reaching applications for assessment and targeting of plant secondary pathway genes, from poorly studied or recalcitrant plant species, that are important in pharmacological, food and process industries. The functional RNAi vector identified in the model system was transformed into onion. Endogenous lfs transcript levels were successfully reduced by up to 43-fold in six transgenic lines. In consequence, LFS enzyme activity was decreased by up to 1573-fold and this observation was supported by Western analysis for the LFS protein. Furthermore, the production of the deterrent LF upon tissue disruption was reduced up to 67-fold. Subjective olfactory assessment of silenced lines indicated that the pungent odour given off by the leaf and bulb material was much reduced compared with that of non-transgenic counterparts, and that this was replaced by a sweeter milder onion odour. A novel colorimetric assay demonstrated that this silencing had shifted the 1-PRENCSO breakdown pathway so that by reducing LFS protein, more 1-propenyl sulfenic acid was converted into di-1-propenyl thiosulfinate. A consequence of the raised thiosulfinates levels was a marked increase in the downstream production of a non-enzymatically produced zwiebelane isomer that has never previously been identified, and other volatile compounds, di-1-propenyl disulfides and 2-mercapto-3,4-dimethyl-2,3-dihydrothiophenes, which had previously been reported either in small amounts or had not been detected in onions. These raised volatile sulfur compounds provide an explanation for the unique flavour notes of the LF reduced onion and are predicted to have health benefits akin to those found in garlic. These results demonstrated that silencing of LFS enzyme activity by introducing an RNAi construct directed against the lfs gene sequence simultaneously reduced levels of the deterrent LF and increased the desirable thiosulfinates in onions.

Made available in DSpace on 2016-08-12T19:15:28Z (GMT). No. of bitstreams: 1 JoseNJ_DISSERT.pdf: 584631 bytes, checksum: ee1c70f7b6370b066911d4581f27c977 (MD5) Previous issue date: 2014-07-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The municipalities of Baraúna and Mossoró-RN establishing itself as the new center for the production of onions. However, the lack of specific fertilizer recommendation for this crop in the region and to quantify parameters of fertilizer application through fertigation is an obstacle to achieving higher crop yields. Aiming to evaluate the yield and quality of onion bulbs in terms of phosphorus an experiment was conducted in the period April to September 2013, at the Experimental Farm Rafael Fernandes, Federal Rural University of Semi-Arid (UFERSA), Mossoró -RN. The experimental design was complete with six treatments and four replications blocks. The treatments consisted of doses of 0, 25, 50, 75, 100 and 125% of the recommended phosphate fertilizer for onions in the State of Pernambuco, corresponding to a fertilizer with 0.00; 33.75; 67.50; 101.25; 135.00 and 168.75 kg ha-1 P2O5, respectively. The cultivar used was Vale Ouro IPA 11. The characteristics evaluated were: plant dry matter, phosphorus content in leaf, business productivity, non-commercial productivity, total factor productivity, commercial classification of bulbs, longitudinal diameter, transverse diameter, the relationship between longitudinal and transverse diameter of the bulbs, soluble solids, titratable acidity, soluble solids ratio and acidity, poignancy, hydrogenic potential (pH) and economic indicators (gross income, net income, rate of return and profitability index). Phosphorus application did not significantly affect the quality of onion. The dose of 168.75 kg ha-1 P2O5 provided the highest business productivity, gross income, net income, rate of return and profitability index. The maximum technical efficiency for IPA 11 cultivar was obtained at a dose of 86.63 kg ha-1 of P2O5 / Os municípios de Baraúna e Mossoró-RN vêm se firmando como novo pólo de produção de cebola. Todavia, a falta de recomendação de adubação específica para essa cultura na região e de parâmetros para quantificar a aplicação de adubos via fertirrigação representa um entrave para a obtenção de maiores rendimentos da cultura. Com o objetivo de avaliar a produtividade e a qualidade de bulbos de cebola em função de doses de fósforo foi desenvolvido um experimento no período de abril a setembro de 2013, na Fazenda Experimental Rafael Fernandes da Universidade Federal Rural do Semi-Árido (UFERSA), Mossoró-RN. O delineamento experimental utilizado foi em blocos casualizados completos com seis tratamentos e quatro repetições. Os tratamentos foram constituídos pelas doses de 0, 25, 50, 75, 100 e 125% da adubação fosfatada recomendada para cebola no Estado de Pernambuco, correspondendo a uma adubação com 0,00; 33,75; 67,50; 101,25; 135,00 e 168,75 kg ha-1 de P2O5, respectivamente. A cultivar utilizada foi a Vale Ouro IPA 11. As características avaliadas foram: massa seca da planta, teor de fósforo na folha, produtividade comercial, produtividade não comercial, produtividade total, classificação comercial de bulbos, diâmetro longitudinal, diâmetro transversal, relação entre o diâmetro longitudinal e transversal dos bulbos, sólidos solúveis, acidez titulável, relação entre sólidos solúveis e acidez titulável, pungência, potencial Hidrogeniônico (pH) e indicadores econômicos (renda bruta, renda líquida, taxa de retorno e índice de lucratividade). A aplicação de fósforo não influenciou significativamente as características de qualidade da cebola. A dose de 168,75 kg ha-1 de P2O5 proporcionou a maior produtividade comercial, renda bruta, renda líquida, taxa de retorno e índice de lucratividade. A máxima eficiência técnica para a cultivar IPA 11 foi obtida na dose de 86,63 kg ha-1 de P2O5

Made available in DSpace on 2016-08-12T19:18:47Z (GMT). No. of bitstreams: 1 JoseNJ_DISSERT.pdf: 584631 bytes, checksum: ee1c70f7b6370b066911d4581f27c977 (MD5) Previous issue date: 2014-07-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The municipalities of Baraúna and Mossoró-RN establishing itself as the new center for the production of onions. However, the lack of specific fertilizer recommendation for this crop in the region and to quantify parameters of fertilizer application through fertigation is an obstacle to achieving higher crop yields. Aiming to evaluate the yield and quality of onion bulbs in terms of phosphorus an experiment was conducted in the period April to September 2013, at the Experimental Farm Rafael Fernandes, Federal Rural University of Semi-Arid (UFERSA), Mossoró -RN. The experimental design was complete with six treatments and four replications blocks. The treatments consisted of doses of 0, 25, 50, 75, 100 and 125% of the recommended phosphate fertilizer for onions in the State of Pernambuco, corresponding to a fertilizer with 0.00; 33.75; 67.50; 101.25; 135.00 and 168.75 kg ha-1 P2O5, respectively. The cultivar used was Vale Ouro IPA 11. The characteristics evaluated were: plant dry matter, phosphorus content in leaf, business productivity, non-commercial productivity, total factor productivity, commercial classification of bulbs, longitudinal diameter, transverse diameter, the relationship between longitudinal and transverse diameter of the bulbs, soluble solids, titratable acidity, soluble solids ratio and acidity, poignancy, hydrogenic potential (pH) and economic indicators (gross income, net income, rate of return and profitability index). Phosphorus application did not significantly affect the quality of onion. The dose of 168.75 kg ha-1 P2O5 provided the highest business productivity, gross income, net income, rate of return and profitability index. The maximum technical efficiency for IPA 11 cultivar was obtained at a dose of 86.63 kg ha-1 of P2O5 / Os municípios de Baraúna e Mossoró-RN vêm se firmando como novo pólo de produção de cebola. Todavia, a falta de recomendação de adubação específica para essa cultura na região e de parâmetros para quantificar a aplicação de adubos via fertirrigação representa um entrave para a obtenção de maiores rendimentos da cultura. Com o objetivo de avaliar a produtividade e a qualidade de bulbos de cebola em função de doses de fósforo foi desenvolvido um experimento no período de abril a setembro de 2013, na Fazenda Experimental Rafael Fernandes da Universidade Federal Rural do Semi-Árido (UFERSA), Mossoró-RN. O delineamento experimental utilizado foi em blocos casualizados completos com seis tratamentos e quatro repetições. Os tratamentos foram constituídos pelas doses de 0, 25, 50, 75, 100 e 125% da adubação fosfatada recomendada para cebola no Estado de Pernambuco, correspondendo a uma adubação com 0,00; 33,75; 67,50; 101,25; 135,00 e 168,75 kg ha-1 de P2O5, respectivamente. A cultivar utilizada foi a Vale Ouro IPA 11. As características avaliadas foram: massa seca da planta, teor de fósforo na folha, produtividade comercial, produtividade não comercial, produtividade total, classificação comercial de bulbos, diâmetro longitudinal, diâmetro transversal, relação entre o diâmetro longitudinal e transversal dos bulbos, sólidos solúveis, acidez titulável, relação entre sólidos solúveis e acidez titulável, pungência, potencial Hidrogeniônico (pH) e indicadores econômicos (renda bruta, renda líquida, taxa de retorno e índice de lucratividade). A aplicação de fósforo não influenciou significativamente as características de qualidade da cebola. A dose de 168,75 kg ha-1 de P2O5 proporcionou a maior produtividade comercial, renda bruta, renda líquida, taxa de retorno e índice de lucratividade. A máxima eficiência técnica para a cultivar IPA 11 foi obtida na dose de 86,63 kg ha-1 de P2O5

A abertura econômica (1990) e a consolidação do tratado do Mercosul (1995) provocaram mudanças nas estruturas de produção e comercialização da cebola no Brasil na década de 90. A principal mudança observada foi com a integração comercial entre Brasil e Argentina, quando o mercado brasileiro (que era auto-suficiente) passou a ter maior participação da cebola do país vizinho e os agentes do mercado passaram a diferenciar produto estrangeiro em relação ao doméstico. Assim, o presente trabalho procurou estimar funções de oferta e demanda do bulbo importado para o Brasil. Para análise foram desenvolvidos um modelo teórico e um modelo gráfico, que auxiliaram na especificação do modelo econométrico para o produto em estudo. O modelo foi ajustado por equações simultâneas utilizando o método de Mínimos Quadrados de Dois Estágios. Os coeficientes encontrados apresentaram sinais coerentes com o modelo econômico teórico definido. Os resultados obtidos permitiram interpretar a dinâmica do mercado importador de cebola argentina. Ficou claro que há um efeito importante do preço (e, portanto, da disponibilidade) de cebola nacional sobre o preço que será pago à cebola argentina. Os argentinos comportam-se como tomadores de preços e são altamente sensíveis ao comportamento do mercado brasileiro. O volume exportado pelos argentinos responde expressivamente ao preço pago no Brasil e à taxa de câmbio da moeda brasileira. O Mercosul gerou uma efetiva integração do mercado da cebola entre Brasil e Argentina, a qual trouxe conseqüências para a produção e o consumo em ambos. / The economic market opening (1990) and the consolidation of the Mercosul agreement (1995) promoted changes in the framework of production and marketing of onion in Brazil in the 1990’s. The main change noticed was the market integration between Brazil and Argentina, when the Brazilian market - which was self-sufficient then – started to have more participation in the market of the neighbor country and the market agents started to differ foreign from domestic products. Thus, this current study aimed to estimate the supply and demand for the bulb imported to Brazil. For the analysis, a theoretical and a graphic model were developed, which helped specify the econometric model for the product of study. The model was adjusted by the simultaneous equations of Minimum Square of Two Stages. The coefficients found showed coherent signs to the defined economic theoretical model. The results obtained allowed to interpret the dynamic of the Argentine onion importing market. It was clear that there is an important effect of price (and, therefore, of the availability) of domestic onion to the price which will be paid for the Argentine onion. The Argentine behaves as price takers and are highly sensitive to the Brazilian market behavior. The amount exported by the Argentina are affected expressively the prices practiced in Brazil and by the exchange rate of the Brazilian currency. The Mercosul generated an effective integration between Brazil and Argentina, which has brought consequences to the production and consumption in both countries.