Phytotoxic Effects of Crude Oil Contamination on Maize Growth Parameters

This study evaluated the phytotoxic and biochemical effects of crude oil contamination on the growth and physiology of maize (Zea mays L.) cultivated in artificially polluted soil. Bonny Light crude oil was introduced at 0 mL/kg (control), 2 mL/kg, 3 mL/kg, and 4 mL/kg soil concentrations, and plants were grown for eight weeks in a greenhouse using a completely randomised design. Germination percentage declined progressively from 90% in the control to 60% at 4 mL/kg, while mean plant height reduced from 84.5 cm (control) to 46.7 cm in the highest treatment. Correspondingly, dry shoot biomass decreased from 6.42 g in the control to 2.85 g in the 4 mL/kg group, and the anthesis–silking interval extended from 2 days in the control to 6 days under maximum contamination. Chlorophyll a and b contents declined significantly (p < 0.05) from 1.32 mg/g and 0.94 mg/g in control plants to 0.71 mg/g and 0.46 mg/g, respectively, in the most polluted soil, indicating suppressed photosynthetic efficiency. In contrast, malondialdehyde (MDA) concentration increased from 0.42 µmol/g in the control to 1.11 µmol/g in the 4 mL/kg group, confirming membrane lipid peroxidation. Activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) increased by 1.6-, 2.1-, and 1.8-fold, respectively, suggesting a compensatory antioxidant response. These results demonstrate that crude oil stress impairs maize development by inducing oxidative damage and metabolic disruption, while enhanced antioxidant enzyme activities represent adaptive defence mechanisms against petroleum toxicity.