Genotoxic Effect of Heavy Metals Cr, Cu, Pb and Zn Using Allium Cepa L.

M. N. Abubacker¹ and C. Sathya²

¹Department of Biotechnology, National College, Tiruchirappalli 620 001, Tamil Nadu, India.

²Department of Botany, Seethalakshmi Ramaswami College, Tiruchirapalli 620 002, Tamil Nadu, India.

DOI : http://dx.doi.org/10.13005/bbra/2559

ABSTRACT: Angiosperms are recognized as appropriate genetic models to detect heavy metal based environmental mutagens and are used in monitoring studies. Allium cepa (onion) has been used to evaluate DNA damages like chromosome aberrations and abnormalities in the mitotic cycle. The aim of the present study is to analyze the cytotoxic effects of chromium, copper, lead and zinc in A. cepa root tip squash mitotic cell divisions. The root tips were treated with three concentrations, viz. 5, 10 and 20 mg/100 ml of chromium, copper, lead and zinc at room temperature for 24 h. Mitotic indices and chromosomal abnormalities were calculated. It was observed that these heavy metals induced different types of chromosomal abnormalities comprising of Chromosome break, Chromosome bridge, C-mitosis, Vagrant, Delayed Anaphase and Vagrant, Chromosome Loss, Polyploidy and Chromosome Bridge, Chromosome Loss and Loculated Nucles, Stickiness, Multipolarity and Polyploid prophase along with the increasing doses. The effect of chromium and lead at 20 mg/100 ml concentration was found to be more toxic rather than copper and zinc to the root meristem of A. cepa. The ranking of cytotoxic potentials was in the descending order: lead > chromium > copper > zinc.

KEYWORDS: Allium cepa; Chromosomal Abnormalities; Heavy Metals; Mitotic Index

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