Cytotoxic and genotoxic effects of the herbicide aclonifen on root meristem cells of Allium cepa L.

An assessment via mitotic index, micronucleus, and chromosomal aberration analyses

Abstract

Abstract

Aclonifen is a selective diphenyl ether herbicide widely used in agriculture for weed control; however, information on its cytotoxic and genotoxic effects on non-target plant cells remains limited. This study investigated such effects of aclonifen on root meristem cells of Allium cepa L. Owing to the low aqueous solubility of aclonifen, all test solutions were prepared in 1% dimethyl sulfoxide, and the final dimethyl sulfoxide concentration was kept constant at 1% in every group. In a preliminary root growth inhibition assay, the 96-hour concentration reducing root length to 50% of the control was determined as 100 parts per million; accordingly, concentrations of 50, 100, and 200 parts per million — corresponding to one-half, one-fold, and twofold this value — were used in the cytogenetic analyses. Distilled water containing 1% dimethyl sulfoxide served as the solvent and negative control, and 10 milligrams per liter methyl methanesulfonate as the positive control. Onion roots were exposed for 24, 48, and 72 hours; for each group, a total of 5000 cells from five biological replicates were scored, and root length, root weight, mitotic index, micronucleus frequency, and chromosomal aberration frequency were evaluated. Data were analyzed by one-way analysis of variance followed by Dunnett's test, with statistical significance set at p < 0.05. Aclonifen treatments significantly reduced root growth and mitotic index values in a concentration- and time-dependent manner, while markedly increasing the frequencies of micronuclei and chromosomal aberrations. The most commonly observed aberrations were chromosome laggards, stickiness, anaphase bridges, and c-mitosis, suggesting both aneugenic and clastogenic modes of action. The highest concentration of aclonifen produced effects comparable to those of methyl methanesulfonate. Aclonifen induces cytotoxic and genotoxic effects on root meristem cells of Allium cepa, highlighting the value of plant-based bioassays in environmental risk assessment.