Cytotoxicological Response of Zea mays to Crude Oil: The Ecological Effects of Exposure to Contaminants

Cytotoxicity of different concentrations of crude oil on Zea mays a widely cultivated crop in Nigeria was investigated for 21 days, using physicochemical and cytotoxicity assay. The experiment was conducted in green-house under controlled environmental conditions. The cytotoxic effects were determined based on the changes in growth rate and cellular morphology of the crop plant. Results obtained showed that pH of the polluted soils is in the range of 4.4 – 4.9, while the unpolluted sample was 7.0. The values obtained for exchangeable base, effective cation exchange capacity, organic carbon, total hydrocarbon were higher in the polluted soil samples compared to the unpolluted soil sample. However, nitrogen, phosphorus and conductivity values were higher in the unpolluted soil sample than in the polluted. Results of the investigation revealed that the crude oil polluted soil affected negatively the growth parameters of Zea mays as the number of leaves, plant height, and total leaf area were reduced in the exposed plant sample compared to the unexposed. A disproportionate increase in cell size (hypertrophy) of new cells which later ruptures as the get cells get older was observed in the cells of plants exposed to crude oil than in the unexposed plant. The concentrations of heavy metals Pb, Cu, Cr, Ni, Zn and Cd in the polluted oil samples were higher in the polluted soil. However, the total hydrocarbon content of the polluted soil samples correlated positively with the heavy metal content and plant biomass of the polluted samples. This study therefore confirms the cytotoxicity effects of crude oil on a common plant, which produces one of the staple foods in Nigeria. Remediation measures should be adopted to reduce the impact of crude oil on the plant sample used especially in area where oil activities are going on.