Physiological, biochemical, and gene expression responses of vetiver grass (Chrysopogon zizanioides) to petroleum hydrocarbon contaminated soil

Petroleum hydrocarbon contamination poses a persistent challenge to soil quality and plant productivity. This study investigated the responses of vetiver grass (Chrysopogon zizanioides) to petroleum hydrocarbon–contaminated soil by integrating physiological, biochemical, and gene expression analyses under controlled pot conditions. Vetiver plants were exposed to increasing levels of total petroleum hydrocarbons (TPH), and plant growth parameters, antioxidant enzyme activities, glutathione dynamics, secondary metabolites, and the expression of GST and PAL genes were evaluated. The results showed that vetiver tolerated petroleum hydrocarbon stress and exhibited measurable changes in antioxidant defense systems and stress-related gene expression. TPH reduction in planted soils ranged from 85 to 93% relative to initial concentrations, while unplanted control soils were used to account for background degradation and natural attenuation. Elevated activities of antioxidant enzymes and increased expression of GST and PAL were interpreted as stress-responsive indicators rather than direct mechanistic drivers of hydrocarbon removal. Overall, the findings demonstrate the adaptive physiological and molecular responses of vetiver grass to petroleum hydrocarbon contamination under controlled conditions. While these results highlight the potential of vetiver for use in plant-based remediation strategies, further field-scale studies are required to validate its effectiveness under real environmental conditions.