Efeitos do Cromo Hexavalente Sobre o Crescimento de Raízes e Ciclo Celular no Meristema da Ponta da Raiz de Allium cepa

M.H.P Costa,C.A.M Rocha,P.C.C Silva

doi:10.18561/2179-5746/biotaamazonia.v6n3p40-44

Abstract

The International Agency Research on Cancer (IARC) classifies the hexavalent chromium [Cr (VI)] as carcinogenic to humans. The major source of environmental contamination by chromium in aquatic ecosystems is related to industrial application of this metal. In this study, we evaluated the cytotoxic and genotoxic effects of Cr (VI) in cell cycle meristem of Allium cepa root. The test was used to evaluate the effects of chromium on seed germination, root elongation, mitotic index and the induction of micronuclei and anomalies of the mitotic cycle. Allium cepa seeds were germinated in five different conditions: (1) negative control, distilled water; (2) test group T1, treated with potassium dichromate 6 mg.L -1 ; (3) test group T2, treated with potassium dichromate 12 mg.L -1 ; (4) test group T3, treated with potassium dichromate 24 mg.L -1 ; (5) positive control, treated with NMU (N-nitroso-N-methylurea) 0,125 mg.L -1 . The statistical analyses used were ANOVA and Pearson's correlation coefficient. Though without affecting the seed germination rate and elongation of roots, the results demonstrated cytotoxic effects on the mitotic index, as well as genotoxic effects of hexavalent chromium. Keywords : Chromium; Allium cepa ; cell cycle; cytotoxicity; genotoxicity.

Highlights

We evaluated the cytotoxic and genotoxic effects of Cr (VI) in cell cycle meristem of Allium cepa root
The test was used to evaluate the effects of chromium on seed germination, root elongation, mitotic index and the induction of micronuclei and anomalies of the mitotic cycle
Allium cepa seeds were germinated in five different conditions: (1) negative control, distilled water; (2) test group T1, treated with potassium dichromate 6 mg.L-1; (3) test group T2, treated with potassium dichromate 12 mg.L-1; (4) test group T3, treated with potassium dichromate 24 mg.L-1; (5) positive control, treated with NMU (N-nitroso-N-methylurea) 0,125 mg.L-1

Summary

Biota Amazônia

Análises de Citotoxicidade e Genotoxicidade Foram analisadas 5000 células / réplica / tratamento, observando-se o número de células em cada fase da mitose (prófase, metáfase, anáfase e telófase). O índice mitótico (IM) foi obtido através da seguinte equação (PIRES et al, 2001): IM= (m/T) x 100, sendo que m = número de células em mitose e T = número total de células analisadas. Além dos micronúcleos (MN), considerados como anomalias interfásicas (AI), foram também consideradas as seguintes anomalias do ciclo mitótico (ACM): ponte anafásica (PA), ponte telofásica (PT), cromossomo vagante (CV) e metáfase irregular (MI) (PINHO et al, 2010; CABARAVDIC, 2010; PAIXÃO; COSTA, 2013). Análise Estatística Análises de variância (ANOVA) foram utilizadas para testar os dados obtidos no índice de germinação de sementes, crescimento de raízes e efeitos genotóxicos do cromo [Cr (VI)] na formação de micronúcleos e de anomalias no ciclo mitótico. As análises estatísticas foram efetuadas com o software estatístico BioEstat 5.0 (AYRES et al, 2007)

Efeitos do Cromo na Germinação de Sementes e Alongamento das Raízes

Total de células analisadas

Tratamentos mitótico