Comparative assessment of physiological and biochemical changes in the selected plant species growing under hydrocarbon stress

Hydrocarbons have become a serious environmental problem due to industrialization and extensive use of vehicles. Various plant species shows a range of stress responses and adaptations to survive in hydrocarbon stress. This study was conducted to investigate the comparative phytotoxicity of polycyclic aromatic hydrocarbons (PAHs) on plants growing under hydrocarbon stress on the germination and to evaluate the response on seedling growth. For the study, two crop plant species (Brassica juncea L. Czern., and Triticum aestivum L.) and two ornamental plant species (Tagetes erecta L. and Helianthus annuus L.) were taken. Pot experiments were conducted in triplicates of 10 days old seedlings treated with 5, 20, 50 & 100 mg kg-1 concentrations of hydrocarbons. After 20 days, biochemical analysis and antioxidant enzyme activity of these plants were studied. Polyphenol and proline increased with increasing concentration of hydrocarbons which were maximum in H. annuus with 0.909 mg g-1 polyphenol and 0.732 µmol g-1 proline at 100 mg kg-1. Increase in antioxidant enzymatic activities was observed with increasing concentration. H. annuus showed maximum activity at 100 ppm which was ascorbate peroxidase (20.37 Unit g-1 FW), peroxidase (0.212 Unit g-1 FW) and superoxide dismutase (2.13 Unit g-1 FW). HPLC analysis in plants and soil provided the concentration of hydrocarbons present in plants species after 20 days taken up from the treated soil. Plants cultivated in 100 mg kg-1 concentration were analysed and the lowest toxicity observed in H. annuus which was 3.013 mg kg-1 Naphthalene, 7.750 mg kg-1 Phenanthrene and 5.691 mg kg-1 Anthracene while highest toxicity was observed in Tagetes at 8.476 mg kg-1 Naphthalene, 0.398 mg kg-1 Phenanthrene and 0.416 mg kg-1 Anthracene. These results suggested that H. annuus can be adopted in phytoremediation of hydrocarbons soil.