Responses of wild plant species to polycyclic aromatic hydrocarbons in soil

Abstract

Responses of plants to polycyclic aromatic hydrocarbons (PAHs) contamination were determined with fifty-five Korean wild plants. Responsiveness of species was evaluated based on germination and shoot weight and shoot length of plants grown in soil spiked with four PAHs (pyrene, fluorene, phenanthrene and fluoranthene). Seeds of test plants were germinated with mixtures of PAHs of 0, 10, 30, 100, 300 mg kg⁻¹ spiked in soil. Seed germination of test plants changed when subjected to PAHs. As compared to control germination percentages ranged from 0 (completely inhibited) to 242.9% (highly promoted) of control at 300 mg kg⁻¹ of PAHs. In germination responses, Fabaceae plants were much less affected (105% of control) compared to species belonging to Caryophyllaceae (18.7% of control), which showed highly susceptible responses. Results demonstrated that seed germination was affected by species-specific responses to PAHs. In seedling growth experiments on Bromus tectorum and Veronica persica, species classified as highly susceptible in germination experiments, a low No Observed Effect Concentration (NOEC) of 10 mg kg⁻¹ was observed. On the other hand, NOEC was 100 mg kg⁻¹ in Bromus japonicus and Cerastium holosteoides var. hallaisanense, which were also classified as highly susceptible by the germination experiment. However, most species classified as susceptible showed high NOEC of greater than 10 mg kg⁻¹. EC₅₀ values of test species ranged from 2.87 × 10² (Humulus japonicus) to 8.05 × 10⁸¹ mg kg⁻¹ (Bidens bipinnata) based on shoot length. The wide range of EC₅₀ for shoot weight suggests that shoot weight is more appropriate as an endpoint for PAHs toxicity than shoot length for determining the susceptibility of plant species to PAHs. It was confirmed that dose-response of plants to PAHs spiked soil can be used to estimate critical concentration of PAHs inhibiting early establishment of plants in contaminated fields.