Naphthalene Stress Responses of the Aquatic fern Azolla Filiculoides Lam. and Evaluation of Phytoremediation Potential

The present study examined the naphthalene stress responses of the aquatic fern Azolla filiculoides Lam. and evaluated its phytoremediation potential. A. filiculoides were grown in nitrogen (N)-free Hoagland containing 25, 50, and 75 mg L-1 naphthalene in the greenhouse. At 75 mgL(-1) naphthalene concentration, the percentage of plant growth and relative growth rates were 118% and 0,09 gg(-1)d(-1) respectively. Photosynthetic pigment contents increased in parallel with the increasing naphthalene concentrations on the third day. In 75 mg L-1 naphthalene, the flavonoid and phenolic contents of the plant increased as secondary metabolites compared to the control. Gas Chromatography-Mass Spectrometry analysis showed that naphthalene is absorbed, accumulated and/or biodegraded by the A. filiculoides. Percentages of biodegradation from planted samples treated with all naphthalene concentrations on day 10 were >= 94% compared to unplanted controls. Data on growth parameters, photosynthetic pigments and secondary metabolite contents, and biodegradation percentages indicated that the effective phytoremediation potential of A. filiculoides for naphthalene was <= 75 mg L-1. In conclusion, the biodegradation values of over 90% obtained in a short time from the planted samples compared to the unplanted controls showed that A. filiculoides tolerates naphthalene stress highly, is effective in its phytoremediation and can be used efficiently.