The genotoxic effect of lead and zinc on bambara groundnut (Vigna subterranean)

Abstract

The effects of lead and zinc treatments on the chromosomes of bambara groundnut was investigated. The seeds of bambara groundnut were placed in Petri dishes in three replicates and allowed to germinate for five days in different concentrations: 25, 50 and 100 mg/L of both lead and zinc nitrates while the control group had distilled water. The total aberrations were examined. The mitotic index was calculated and the results were statistically evaluated by the analysis of variance at 5% significant level. The mitotic index decreased as the concentration increased (p<0.05). The highest mitotic index value was 3.40±0.88 for the control while the least was 1.30±0.48 for the 100 mg/L Pb treatment. The results show the most frequent chromosomal anomalies induced by these heavy metals as stickiness and bridges. Pb is much more genotoxic than Zn, as it induced more aberrations having percentage abnormalities of 92.3% while Zn had 30.0% for the highest concentration tested. Increased metal pollution can lead to some irreversible cytogenetic effects in plants and higher organisms. The study is an attempt to corroborate the toxic effect of lead and zinc on the chromosomes of plants. These results will be useful in environmental monitoring of the cytotoxicity of metals.

Key words: Heavy metal, aberrations, genotoxic, cytogenetic, mitotic index.