The effects of the food preservatives potassium metabisulphite (PMB) and potassium nitrate (PN) have been studied on root tips of Allium cepa L. (variety Kantartopu-3). Roots of A.cepa were treated with a series of concentrations, ranging from 50 ppm to 100,000 ppm for 3, 6, 12, 24 and 48 h. Examinations of roots were done in permanent root tip squash preparations stained by the Feulgen technique. PMB and PN effect on the relative duration of each mitotic stage as compared with the control. They are also caused reduction in the mitotic index, indicating mitotic inhibition and increased frequency of abnormal mitosis.
The type of abnormalities induced are chromosome stickiness, c-metaphase, anaphase and telophase bridges, disturbed chromosomes of anaphase and telophase stages, anaphase lagging and forward chromosomes at anaphase and telophase and micronuclei formation at intephase cells.