The role of temperature in phenanthrene transfer and accumulation in crop leaves

Polycyclic aromatic hydrocarbons (PAHs) pollution has become a worldwide environmental problem, and the spread of PAHs can cause carcinogenicity, mutagenicity, and toxicity to humans. However, the transfer and accumulation of PAHs in crop leaves has not been clearly understood. In this study, we first reported that the environmental temperature could induce phenanthrene transfer and accumulation in hydrocultured wheat, corn and soybean leaves via vacuum-infiltration-centrifugation method. Phenanthrene accumulation rises significantly (p < 0.05) in the first 8 h and reaches the maximum accumulation rate at the 4th h. Then the accumulation turns stable in both apoplast and sympalst of wheat, soybean and corn leaves. Temperature is positively correlated with phenanthrene accumulation in apoplast and sympalst of soybean and corn leaves, and phenanthrene accumulation increases under lower temperature in apoplast and sympalst of wheat leaves. Temperature also displays a positive correlation with the phenanthrene accumulation under gradient phenanthrene treatments in both apoplast and sympalst. In addition, the wheat, corn and soybean leaves have the same phenanthrene accumulation pathways and symplast pathway is major for phenanthrene accumulation with the contribution over 55% in total phenanthrene accumulation. Meanwhile, based on the Elovich equation, the symplast and apoplast processes of phenanthrene accumulation are endothermic. In the end, our findings will offer a new understanding for phenanthrene transfer and accumulation pathway in plant leaves and put forward a new biological reference of PAHs transfer in environmental science.