Effects of Petroleum Products in Soil on α-Amylase, Starch Phosphorylase and Peroxidase Activities in Cowpea and Maize Seedlings

Aims: To determine the effect of petroleum products (kerosene, diesel, engine oil and petrol) contaminated soil at various concentrations on the activities of α-amylase, starch phosphorylase in the cotyledons of cowpea and maize seedlings as well as peroxidase activity in the leaves of both seedlings.

Place and Duration of Study: This study was conducted in Delta State University, Abraka, Nigeria between April 2007 and August 2011.

Methodology: Improved varieties of maize (Zea mays L) and Vigna unguiculata (L) Walp were planted in soil contaminated at different concentrations comprising six groups. Each group was replicated five times. Groups 1 to 5 contained 0.1%, 0.25%, 0.5%, 1.0% and 2.0% (v/w) respectively of each of the petroleum products while group six served as control (0.0%). Three seeds were planted in each bag and watered daily. Four days after germination the activities of α-amylase, starch phosphorylase in the cotyledons of the cowpea and maize seedlings were analysed. This was followed by the determination of peroxidase activity in the leaves of cowpea and maize seedlings four, eight and twelve days after germination.

Results: The results showed that the petroleum products caused metabolic perturbations in the seedlings. This is indicated by the significant (P<0.05) decrease in the activities of starch degrading enzymes: α-amylase and phosphorylase as well as peroxidase activity compared to their respective control values.

Conclusion: Kerosene decreased the activities of the enzymes more than the other petroleum products. The effect of petroleum products contaminated soil was more severe in cowpea seedlings relative to maize seedlings.