ABSTRACT
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.
Subject(s)
Environmental Monitoring , Toxicity Tests , Water Pollutants, Chemical/toxicity , Brazil , DNA Damage , Fresh Water , Mitotic Index , Onions/drug effects , Plant Roots , SeasonsABSTRACT
The present study aimed to verify the genotoxic and citotoxic potential in water samples from the basin of Tapanhon River, Pindamonhangaba, São Paulo, by using the Allium test. Water samples of the Tapanhon River and its affluents (the Primeira Água and Segunda Água Streams, the Galega Brook) as well as a sample from the Borba Spring have been collected for negative control. Six bulbs of Allium cepa have been submitted to each of the samples for 24 hours. The roots have been fixed in ethanol/acetic acid 3:1; they have also been submitted to the Feulgen reaction, and the meristematic portion has been crushed in slide for cellular analysis. As such, 6000 cells have been collected for evaluation of the mitotic index (MI) and micronuclei (MNC) as well as 300 cells in the metaphase and anaphase phases, to evaluate chromosome aberrations (CA). No MNC has been found in the samples tested. The MI values have shown to be elevated in all samples tested when compared to the control with statistical relevance, however, only for the samples from the Primeira Água Stream and the Galega Brook (p<0,05). Chromosome aberrations have been observed in all samples (p<0,05). These data suggest that along this bay there are substances which induce the citotoxic and genotoxic effects, which, in turn, have promoted alterations in the organism tested.
O presente trabalho teve como objetivo verificar o potencial citotóxico e genotóxico em amostras de água da bacia do rio Tapanhon, Pindamonhangaba, São Paulo, utilizando o teste Allium. Foram coletadas amostras de água do rio Tapanhon e seus tributários (córregos Primeira Água e Segunda Água, ribeirão Galega) e amostra de nascente da bica Borba para o controle negativo. Seis bulbos de Allium cepa foram submetidos a cada uma das amostras por 24h. As raízes foram fixadas em etanol/ácido acético 3:1, submetidas à reação de Feulgen e a porção meristemática esmagada em lâmina para análise celular. Foram contadas 6000 células, para avaliação do índice mitótico (IM) e micronúcleos (MNC) e 300 células nas fases de metáfase/anáfase, para a avaliação de aberrações cromossômicas (AC). Não foi observado MNC nas amostras testadas. Os valores do IM mostraram-se elevados em todas as amostras testadas quando comparados ao controle, porém com relevância estatística apenas nas amostras do córrego Primeira Água e ribeirão Galega (p < 0,05). Aberrações cromossômicas foram observadas em todas as amostras (p < 0,05). Estes dados sugerem que ao longo desta bacia há substâncias indutoras de efeito citotóxico e genotóxico que promoveram alterações no organismo testado.
