Comparative Cytogenetic Evaluation of 8-Hydroxyquinoline, Paradichlorobenzene, and Colchicine on Mitosis in Allium cepa Root Meristem Cells

Abstract

This study investigates the cytogenetic effects of three chemical mutagens—8-hydroxyquinoline (8-HQ), paradichlorobenzene (PDCB), and colchicine—on the mitotic behaviour of Allium cepa var. aggregatum root meristem cells. Root tips were treated with 0.004 N 8-HQ, 0.1% PDCB, their combinations, and a mixture of all three agents for five hours. Cytological preparations were made using acetoorcein staining and examined microscopically. The untreated control showed normal mitotic stages, while treated samples exhibited various abnormalities including c-metaphase, chromosomal stickiness, lagging and vagrant chromosomes, micronuclei, polyploidy, binucleated cells, giant cells, and multipolar anaphase. Notably, colchicine and PDCB prominently induced c-metaphase and polyploidy, whereas 8-HQ treatments were associated with chromosomal stickiness and anaphase bridges. Combined treatments significantly intensified the frequency and diversity of chromosomal aberrations, suggesting a synergistic mutagenic effect. These results confirm the dose- and time-dependent genotoxic potential of these agents and emphasize their applicability in cytogenetic studies and plant breeding programs targeting genetic improvement through polyploidy induction.