Physiological Responses of Ornamental Plants Grown on Crude Oil-Contaminated Soil

Background and Objective: Soil contamination by crude oil disrupts plant growth and physiology, yet the physiological responses of ornamental plants under such stress remain poorly understood. Physiological reactions of ornamental plants grown on crude oil-contaminated soil were investigated. Materials and Methods: Eighteen polythene bags were filled with 20 kg of soil, arranged at 0.5 m spacing between polybags and 1 m between replications, and perforated at the base to avoid water logging. Unpolluted soil served as control without any treatments. The crude oil concentrations were 0, 15, 30, 45 and 60%. The experiment was laid out in a completely randomized design with 3 replicates. Growth parameters such as plant height, number of leaves, stem girth, and leaf length were measured fortnightly and analyzed using SPSS Version 20. The data were analyzed using ANOVA in SPSS (Version 17), and significant differences were determined by Tukey’s test at a 5% probability level. Results: It showed that adding crude oil altered the physicochemical properties of the experimental soil 2 weeks after spiking. Results obtained showed that there was a significant difference (p<0.05) between heavy metal concentrations in crude oil-polluted soil and the control (unpolluted experimental soils). The changes indicate a slight increase in the concentration of TPH from 22.65 to 21470.67 mg/kg in the 2nd week of the study. The mean plant height of Periwinkle (Catharanthus roseus) was significantly (p<0.05) high at 8 WAP (7.4±1.9 cm) in control while the lowest mean concentration was recorded from 60% treatment (2.9±1.1 cm). Conclusion: Similarly, mean plant girth, number of leaves, and length were significantly high in the control compared to treated soil. The highest mean value of growth parameters in Acalypha indica, Horsetails (Equisetum arvense), and Eranthemum laxiflorum was recorded from the control while the lowest values were recorded from 60% treatment.