Bivalent nickel exposure induced mitotic toxicity in onion root tips

Nickel (Ni) is utilized across multiple industries, resulting in significant environmental contamination and exhibiting various genotoxic effects on plants and animals due to its release into the external environment. This study evaluates the cytotoxic effects of different doses of nickel on onion (Allium cepa L.) root tips. To evaluate the sensitivity of Nickel, bulbs of onion were treated at 10, 25, 50 and 100 ppm along with a control (0 ppm) using NiCl2 salt as the source of Nickel. At elevated concentrations of nickel (100 ppm) in a hydroponic study, the onion roots exhibited browning and translucency, accompanied by a retardation of growth. Various chromosomal anomalies, including chromosomal breaks, laggards, vagrant chromosomes, bridges, distorted chromosomes, sticky chromosomes, c-mitosis etc. were observed following a 24 hr exposure to toxic doses of nickel. Both types of chromosomal abnormalities, namely spindle fibre abnormality (SFA) and chromosomal abnormality (CA), were observed under Ni treatment. The evaluation of cell death in the treated roots was done using the Evans blue dye test. Uptake of Evans blue by the root cells demonstrated the cell death parameter, which served as an indicator of cytotoxicity.