Mineral elements-mediated responses govern cadmium accumulation in plants under C14 alkane stress

The phytoremediation of agricultural soils co-contaminated by cadmium (Cd) and petroleum hydrocarbons presents a significant challenge due to the complex interactions between pollutants. This study investigated the mechanisms governing Cd accumulation in four plant species-Lolium perenne L. (ryegrass), Ricinus communis L. (castor bean), Amaranthus hypochondriacus L. (amaranth), and Mirabilis jalapa L. (mirabilis)-under stress from C14 alkane, a model petroleum hydrocarbon. A concentration gradient of C14 alkane was applied to examine its effects on plant growth, Cd accumulation, and mineral elements uptake. Integrated multivariate analyses, including random forest analysis, mantel tests and structural equation modeling, elucidated the underlying interactions. The results demonstrated that C14 alkane stress significantly inhibited plant growth, with sensitivity varying considerably among species. Crucially, alterations in mineral elements homeostasis were identified as the central mechanism mediating plant responses. Tolerant species (ryegrass, castor bean, mirabilis) displayed a capacity for ionomic adjustment, with elements like manganese (Mn) playing a central yet complex role in modulating both stress response and Cd accumulation pathways. In contrast, the sensitive species (amaranth) failed to maintain this regulation, leading to compromised growth and Cd accumulation. This study establishes that a plant's ionomic regulatory capacity, beyond direct C14 alkane tolerance, is a critical determinant of phytoremediation efficacy. The findings provide a novel theoretical framework for selecting remediation plants and optimizing strategies, such as targeted mineral elements management, for soils co-contaminated with heavy metals and petroleum hydrocarbons.