Effect of oil palm leaf treatment of crude oil impinged soil on biochemical indices of cowpea (vigna unguiculata) seedlings

The possibility of oil palm leaf (OPL) being applied as ameliorative agent in unrefined petroleum oil tainted soil was examined in this study. Six treatment protocols, comprising group 1 (untainted soil), group 2 (untainted soil +50g of OPL), group 3 (untainted soil +100g of OPL), group 4 (petroleum oil tainted soil), group 5 (petroleum oil tainted soil +50g of OPL) and group 6 (petroleum tainted soil +100g of OPL) were used in this study. A decrease in photosynthetic pigments of cowpea seedlings in unrefined oil tainted soil compared to the cowpea seedlings in control was noted. Cowpea seedlings raised in unrefined oil tainted soil had lower levels of antioxidants relative to the control. Conversely, lipid peroxidation was elevated in seedlings raised in unrefined oil tainted soil. The activities of glutathione s- transferase, sulphite oxidase, xanthine oxidase and aldehyde oxidase significantly reduced in cowpea seedlings raised in soil tainted with unrefined oil without addition of OPL as compared to those of the control and all OPL protocols. The significant improvement in photosynthetic pigments, beta carotene as well as the antioxidant profile of cowpea seedlings in untainted soil treated with OPL when compared with those in control group, alongside the substantial ameliorative effect on chlorophyll, beta carotene and the antioxidant profile of cowpea seedlings in OPL amended soil, suggests that OPL addition to unrefined petroleum oil tainted soil reduced petroleum toxicity on cowpea seedlings.