Allium cepa (2n= 16) assay is used to determine cytotoxicity of environmental pollutants like heavy metal arsenic (in the form of arsenic trioxide—concentration used: 0.010, 0.050, 0.075 and 0.100 mg L− 1 for 24 h duration) and azo-dye metanil yellow (concentration used: 100, 150, 200 and 400 mg L− 1 for 24 h duration) with an objective to understand the toxic effects of the test materials on cells and chromosomes of a plant-based system. Assessment of cytotoxicity reveals that arsenic trioxide can induce chromosomal breakages, affects spindle organization and causes cellular metabolic defects; whereas, metanil yellow predominantly affects cellular metabolism. Cytological disturbances are mostly dose-dependent, and arsenic trioxide depicts pronounced effectivity in inducing mitotic aberrations in root tip cells of A. cepa than metanil yellow (in relation to employed doses). Furthermore, aqueous plant extracts (used due to its operational simplicity and cost-effectivity) of the leaf (Coriandrum sativum L., Ocimum tenuiflorum L., and Pteris vittata L.) and seed (Nigella sativa L.) samples are used to ascertain their amelioration potentiality against the environmental toxicants. The ameliorative study (decrement in their observed values) involves attributes like mitotic index, total abnormal dividing cell frequency and frequency of giant and anucleate cells in resting stages. Results suggest that all the employed extracts are ameliorative, and can be explored further for their role in bioremediation.