Physiological effect of phenanthrene on Triticum aestivum, He Ha nth us annus and Medicago sativa

Background: Polycyclic aromatic hydrocarbons (PAHs) are widespread organic pollutants released into the environment by both natural and anthropogenic processes. PAHs can negatively affect different aspects of plant growth and development. However, the mechanisms of PAHs effects and physiological response of plants to PAHs have not been adequately studied. Accordingly, the aim of this study was evaluation of the germination, growth and physiological responses of wheat, sunflower and alfalfa to phenanthrene toxicity. Material and Methods: This experiment was conducted as a pot culture of plants using a completely randomised design (CRD) with four replications. Plants were cultivated in soil containing 50 and 100 mg kg1 of phenanthrene for 14 days under greenhouse conditions. All biochemical assays were performed spectrophotometrically after the determination of growth parameters. Results: Soil contamination with phenanthrene differently decreased seed germination and the subsequent seedling growth of plants. Alfalfa showed the highest resistance at both the seed germination and seedling growth phases. Wheat and sunflower were the most sensitive species at the seed germination stage and seedling growth phase, respectively. Phenanthrene contamination induced oxidative stress in plants and POD was determined to be the important enzyme involved in ROS detoxification. Conclusions: Phenanthrene effects on seed germination, seedling growth and physiological parameters of plants are species-dependent. The induction of oxidative stress and decrease in photosynthetic pigments content are two of the reasons for lower plant growth in phenanthrenecontaminated soil, and POD was an important enzyme in the detoxification of ROS. At least in some species, the higher resistance at seed germination could be followed by the higher resistance of seedlings to PAHs.