Determination of Cytotoxic Impact of Heavy Metals on Plant Cells Using <i.Allium cepa</i> (Onion)

Abstract

The environment faces significant global health challenges due to the presence of heavy metals, with harmful substances being discharged into the lithosphere, hydrosphere, and atmosphere. This study focused on assessing the cytotoxic effects of heavy metals recovered from dumpsites on the meristematic tissue of root tips of Allium cepa L. Soil samples, collected from central dumpsites containing heavy metals, underwent standard procedures. The concentrations of heavy metals in the samples were determined using the Association Official Analytical Chemist (AOAC) method. Each sample was digested with acids, neutralized with Calcium Oxide (CaO), and used to grow Allium cepa at varying concentrations, determining the LD50 of each sample. The LD50 concentrations were then employed to investigate cytotoxic effects on Allium cepa using standard techniques. Processed soil samples yielded Pb, Cr, Cd, Ni, Co, Zn, Fe, and Cu at different concentrations, many of which exceeded the WHO standard values. The mitotic index ranged from 5.34 ± 0.01 to 10.36 ± 0.00, 5.34 ± 0.00 to 13.16 ± 0.01, 3.36 ± 0.01 to 6.81 ± 0.01, 2.48 ± 0.01 to 13.16 ± 0.01, with the control at 13.32 ± 0.01. Chromosomal aberrations, including chromosome break, fragmentation, bridge, vagrant, lesion, and sticky C-mitosis, were observed. These alterations indicated that toxic substances significantly impact DNA sequence.