Evaluation of The Differential Growth Conditions, Heavy Metal Composition And Cytogenetics of <i>Allium cepa</i> By The Use of Chromosome Aberration Bioassay.

Abstract

Comparative study of the suitability of onion bulbs grown in different environmental conditions for the Allium cepa bioassay was undertaken using the chromosome aberration test. Onion bulbs were obtained from Gombe, Kano, Maiduguri, and Sokoto. Cadmium, nickel, selenium, and lead were not detected in Gombe onions. Kano and Maiduguri contained high levels of lead (0.30±0.01 and 0.20±0.01 mg/l) and nickel (0.30±0.01 and 0.30±0.01 mg/l) respectively. The highest zinc and selenium contents were detected in Maiduguri onions (7.40±0.01 and 0.40±0.01 mg/l respectively). Results of cytological studies using the aceto-orcein squash technique showed that Gombe onions had the highest mitotic index while Kano had the least. In the same vein, Gombe onions had the lowest percentage aberrant cells, while Kano had the highest. The mean root lengths of the onion bulbs grown in tap water at 96 h were of the increasing order: Gombe>Sokoto>Maiduguri>Kano. The results of the Allium test indicate Gombe onions were the best and most suitable for A. cepa bioassay as they were relatively free from heavy metal contamination. The findings also show that health risks could be caused to the unsuspecting public by the daily intake of heavy metals through the contaminated vegetables with heavy metals.