The aim of this study was to determine if the cytotoxic and genotoxic responses of Allium cepa are effective biomarkers of harmful effects caused by polluted river water and if changes in the responses reflect seasonality in the harmful effects. Samples were collected in the dry season (August 2011 and 2012) and rainy season (February 2012 and 2013) at sampling points on the Jaguari River and the Ribeirão Lavapés, in Brazil. Allium cepa bulbs were exposed to the samples, to positive controls (15 µg/L methyl methanesulfonate), and to negative controls (tap water). Three root tips from each bulb were then stained using the Feulgen reaction, then the micronucleus frequency, the mitotic index, and mitotic anomalies were measured. The total number of anomalies (stickiness, c-mitosis, multipolarity, chromosome bridges, and unidentified anomalies) in the rainy season (8.61 ± 3.65) and dry season (7.07 ± 2.96) were significantly different (U = 11.31, p = 0.04). Toxicity, indicated by the formation of micronuclei and the mitotic index, was higher in the February 2012 samples than in the August 2012 samples. The mean manganese concentration (0.13 mg/L) in the rainy season samples was higher than the maximum concentration permitted by the Brazilian National Environmental Council (<0.1 mg/L) and the manganese concentrations positively correlated with chromosomal aberration induction (p = 0.01, r = 0.69). In conclusion, the rainy season samples were more toxic than the dry season samples. This was probably related to rain water carrying compounds with potentially negative impacts into the rivers. These findings highlight the importance of biomonitoring studies and of treating wastewater in urban areas.
RESUMO -O objetivo do trabalho foi avaliar o progresso da ferrugem do pessegueiro e a eficiência de fungicidas no controle de da ferrugem e do furo-de-bala em pomares da região metropolitana de Curitiba-PR. Os ensaios foram conduzidos em pomar comercial com o delineamento experimental em blocos ao acaso, Cultivar Chimarrita, com quatro tratamentos (mancozebe, tiofanato metílico, clorotalonil e testemunha, sem pulverização) e quatro repetições, nas safras de 2004/2005 e 2005/2006. Cada fungicida foi pulverizado oito vezes, com intervalo de 15 a 20 dias entre as aplicações. A avaliação do progresso da epidemia de ferrugem e a eficiência dos fungicidas no controle das doenças foram feitas com base na incidência e severidade da doença nas folhas e na porcentagem de desfolha das plantas. A taxa de progresso da doença e o inóculo inicial na testemunha não diferiram significativamente entre os anos. Todos os fungicidas reduziram a desfolha e a severidade da ferrugem, mas o clorotalonil foi melhor e também reduziu a incidência em ambos os anos. Os fungicidas mancozebe e tiofanato metílico reduziram a incidência de furo-de-bala. Termos para indexação: Prunus persica, Tranzschelia discolor, Wilsonomyces carpophilus incidência, controle químico. TEMPORAL PROGRESS OF PEACH RUST AND FUNGICIDES TO CONTROL THE FOLIAR DISEASES OF PEACH TREEABSTRACT -The aim of this study was to evaluate the development of the peach rust in two seasons and, the efficiency of fungicides to control the peach rust and the shot-hole in orchards of the metropolitan region of Curitiba, Paraná, Brazil. The trials were carried out in a commercial orchard and were designed in complete randomized blocks, cv. Chimarrita, with four treatments (mancozeb, thiophanate methyl, chlorothalonil and control-unsprayed) and four replications, in the crop seasons 20004/5 and 2005/06. Each fungicide was sprayed eight times, at 15 to 20 days intervals. The assessment of the epidemic progress and effectiveness of fungicide were performed based on the incidence and severity on leaves and percentage of plants defoliation. The progress rate of the epidemic and the initial inoculum did not differ significantly between years and the logistic model fit to data of both years. All fungicides reduced the defoliation and severity of peach rust, but chlorothalonil was the best and also reduced the incidence in both years. The fungicides mancozeb and thiophanate methyl reduced the shot-hole incidence. Termos para indexação: Prunus persica, Transzchelia discolor, Wilsonomyces carpophilus incidence, chemical control.
Tomando por fio condutor uma importante questão para a teoria do conhecimento na filosofia moderna, a saber, é possível um conhecimento racional da realidade? O presente trabalho tem por objetivo analisar um importante debate realizado no século XVIII entre David Hume e Immanuel Kant na tentativa de dar resposta a esta pergunta. De modo que num primeiro momento nos ocuparemos com a objeção humeana aos procedimentos adotados pela tradição metafísica nas Investigações sobre o entendimento humano. Após apresentar a objeção de Hume, concentrar-nos-emos em apresentar o modo pelo qual Kant por um lado, recepciona a crítica feita por Hume, e por outro recusa as conclusões humeanas conduzindo o problema com vistas a oferecer uma resposta mais sistemática
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