Ecophysiological tolerance of Elodea canadensis to nickel exposure Maria G. Maleva a , Galina F. Nekrasova a , Przemysław Malec b , M.N.V. Prasad c , Kazimierz Strzałka b, * a Department of Plant Physiology and Biochemistry, M. Gorky Ural State University, Lenin av. 51, Ekaterinburg 620000, Russia b Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, ul. Gronostajowa 7, 30-387 Kraków, Poland c Department of Plant Sciences, University of Hyderabad, Hyderabad 500 046, India article info Article history: Received 24 November 2008 Received in revised form 23 June 2009 Accepted 13 July 2009 Available online 18 August 2009 Keywords: Elodea canadensis Metal chelators Nickel Oxidative stress Oxygen exchange Photosynthetic pigments abstract Biological accumulation of nickel and concomitant ecophysiological responses were studied in the leaves of Elodea canadensis treated with different concentrations of Ni (1–50 lM) for 5 d. In low concentrations nickel was accumulated mainly in the soluble protein fraction, which correlated with its highest observed accumulation coefficient. In higher concentrations, Ni binding in the non-protein soluble fraction was observed. The effects of increasing nickel concentrations on the accumulation of photosynthetic pigments, gas exchange rates, lipid peroxidation, biosynthesis of thiol-containing compounds and the activity of selected enzymes – markers of oxidative stress were investigated. The appearance of several new polypeptides with apparent molecular weights below 20 kDa, was found by SDS–PAGE in Ni-treated Elodea leaves. Our results indicate that Ni, in concentrations up to 10 lM could induce sub-lethal oxida- tive stress in Elodea leaves. In response, plants developed detoxification mechanisms including an enhanced biosynthesis of thiol-containing compounds which facilitated Ni accumulation and sequestra- tion in plant tissues effectively. Hence, E. canadensis could be used in the biological removal of Ni from polluted water up to 10 lM concentration. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Nickel is a trace metal occurring ubiquitously in soil, water, air, and in the biosphere. The levels of nickel in natural waters have been found to range from 2 to 10 lg dm À3 (fresh water) and from 0.2 to 0.7 lg dm À3 (marine) (WHO, 1991). In humans and animals, nickel is involved in the metabolism of methionine, of vitamin B-12 and folate, and therefore it is sug- gested that it may be an essential micronutrient (WHO, 1991; Uthus and Seaborn, 1996). In plants, nickel is a cofactor for enzyme urease (Watt and Ludden, 1999). A superoxide dismutase form with Ni ions in its active site has recently been found in bacteria (Barondeau et al., 2004). Nickel contamination of aquatic resources occurs mainly from technogenic sources such as the production of stainless steel, alloys, storage batteries, spark plugs, magnets, electroplating, motor vehicles, aircraft paint, chemical, textile, pigment and machine tool industries. Nickel is one of those heavy metals frequently encountered in industrial effluents. Nickel from electro- plating effluents may range from 2 to 900 mg L À1 , while paint and ink formulation 0–40 mg L À1 , porcelain enameling 0.25–67 mg L À1 and copper sulfate manufacture industries 22 mg L À1 (Patterson, 1977). The exposure to elevated nickel concentrations would be toxic for humans and animals, e.g. nausea, vomiting, diarrhoea causing pulmonary fibrosis, renal edema, skin dermatitis, and gastrointes- tinal distress (Akhtar et al., 2004). Therefore, its removal from natural and waste waters is of particular interest. Recently, electro- deionization has been considered and researched for recovering nickel and the purifying of water from electroplating effluents for industrial reuse (Feng et al., 2007). Biosorption using algae, bacteria, fungi and yeasts microbial biomass as the adsorbent has emerged as a potential alternative technique to the existing conventional physico-chemical methods of the removal of heavy metals from contaminated water (Volesky, 1990; Vasudevan et al., 2001; Axtell et al., 2003; Padmavathy, 2008). Aquatic macrophytes have attracted the attention of ecotoxicol- ogists all over the world to address a wide variety of topics such as the cleanup of water bodies, sewage ponds, domestic primary effluent treatment plants, compost and landfill leachate toxicity studies, the biogeochemical cycling of trace elements in fly ash set- tling ponds, the treatment of coal mining drainage and recalcitrant waste water. Extensive information on nickel uptake/removal from terrestrial environment is available (Palmer et al., 2001). However, there is a need to investigate the use of aquatic macrophytes for the removal of heavy metals. Recently, the kinetics of nickel uptake has been studied in Lemna gibba (Demirezen et al., 2007). Elodea canadensis (Canadian waterweed) is cosmopolitan in distribution. Its ecology has been studied extensively. It is 0045-6535/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2009.07.024 * Corresponding author. Tel.: +48 12 664 65 09; fax: +48 12 664 69 02. E-mail address: strzalka@mol.uj.edu.pl (K. Strzałka). Chemosphere 77 (2009) 392–398 Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere