Responses of Accessions of Zea Mays to Crude Oil Pollution Using Growth Indices and Enzyme Activities as Markers

The performance of every plant in an environment is an indicator on how the plant can withstand various environmental conditions. This study investigates the toxicity of crude oil on growth performance, chlorophyll contents, enzymatic activities, and oxidative stress biomarkers of eight accessions of Zea mays. It assays growth enzyme activities (for amylase and invertase) as well as oxidative stress biomarkers (malondialdehyde, peroxidase, superoxide dismutase, and catalase) in Z. mays, using spectrophotometric method. The maize accessions have been grown in experimental pots with crude oil treatments (2%, 4%, 6%, 8%, and 10%) and harvested after 14 days of seedling emergence. Results show that the percentage seedling emergence, leaf size, root length, stem girth, and shoot length of each accession have decreased significantly (p<0.001, p<0.01, and p<0.05) as pollution level has ascended. Significant differences in chlorophyll content have also been observed in the plants grown in soil samples, polluted by crude oil, compared to non-polluted soil (p<0.0001; p<0.01; p<0.05) with a decrease in growth enzymes activities as well as oxidative stress biomarkers at 10% pollution. TZE Comp 5 accession and BR-9928 DMR SR-Y have been the most resistant and the most sensitive accessions, respectively. Results suggest that parameters, activities, and expression levels of growth enzymes as well as oxidative stress responses can be used as biomarkers to evaluate the influence of crude oil on the growth of Z. mays. They also suggest that there are intraspecific differences in the responses of the accessions of Z. mays to crude oil pollution.