Evidence of sulfur-bound reduced copper in bamboo exposed to high silicon and copper concentrations Blanche Collin a, b, * ,1 , Emmanuel Doelsch c , Catherine Keller a , Patrick Cazevieille c , Marie Tella c , Perrine Chaurand a , Frédéric Panfili b , Jean-Louis Hazemann d , Jean-Dominique Meunier a a CEREGE, CNRS, Aix-Marseille Univ., Europôle méditerranéen de l’Arbois, BP 80, 13545 Aix en Provence, France b Département de recherche développement de la société PHYTOREM S.A., Chemin de l’Autodrome, 13140 Miramas, France c CIRAD, UPR Recyclage et risque, Avenue Agropolis, F-34398 Montpellier, France d Institut Néel, CNRS and Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9, France article info Article history: Received 9 September 2013 Received in revised form 13 December 2013 Accepted 23 December 2013 Keywords: Metal Toxicity Phytoremediation Poaceae X-ray absorption spectroscopy abstract We examined copper (Cu) absorption, distribution and toxicity and the role of a silicon (Si) supple- mentation in the bamboo Phyllostachys fastuosa. Bamboos were maintained in hydroponics for 4 months and submitted to two different Cu (1.5 and 100 mm Cu 2þ ) and Si (0 and 1.1 mM) concentrations. Cu and Si partitioning and Cu speciation were investigated by chemical analysis, microscopic and spectroscopic techniques. Copper was present as Cu(I) and Cu(II) depending on plant parts. Bamboo mainly coped with high Cu exposure by: (i) high Cu sequestration in the root (ii) Cu(II) binding to amino and carboxyl li- gands in roots, and (iii) Cu(I) complexation with both organic and inorganic sulfur ligands in stems and leaves. Silicon supplementation decreased the visible damage induced by high Cu exposure and modified Cu speciation in the leaves where a higher proportion of Cu was present as inorganic Cu(I)S compounds, which may be less toxic. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Phytoremediation technologies are currently used for waste- water treatment (McCutcheon and Schnoor, 2003; Schroder et al., 2007; Vymazal, 2011). Bamboos are known for their high growth rate and biomass production as well as their resistance to a wide range of stress factors (Kleinhenz and Midmore, 2001), and they are well adapted for the wastewater remediation (Arfi et al., 2009). Wastewater from food and farming industries (such as winery (Arfi et al., 2009), animal breeding (Nicholson et al., 1999)) or from other industries (such as printing) can be contaminated by different metals, including copper (Cu), a micro-nutrient that can be toxic at high concentrations and affect the remediation efficiency. Little is known about the absorption and tolerance of metal by bamboos (Collin et al., 2013, 2012). In an hydroponic experiment bamboos, (Gigantocloa sp. “Malay dwarf”) were shown to tolerate a high Cu concentration (Collin et al., 2013) which is known to be toxic for other Poaceae plants such as wheat (Bravin et al., 2010) and Sabi grass (Kopittke et al., 2009). Therefore, in order to improve phytoremediation technology, it is essential to test the extent of Cu tolerance in bamboos and identify mecha- nisms by which bamboos are able to cope with an excess Cu content. Bamboos have been found to be very efficient in accumulating high amounts of silicon (Si) in their tissues, both in natural, i.e. up to 183 mg g 1 SiO 2 (Collin et al., 2012), and hydroponic, i.e. up to 218 mg g 1 SiO 2 conditions (Collin et al., 2013; Epstein, 1994). There is increasing evidence that Si has a role in alleviating metal toxicity in several species (Guntzer et al., 2012; Liang et al., 2007), and Cu toxicity in Arabidopsis thaliana (Khandekar and Leisner, 2011; Li et al., 2008) and in Erica andevalensis (Oliva et al., 2011). Although Collin et al. (2013) showed that a wide range of Si in solution (0e 1.5 mM) did not influence plant growth and development or the Cu concentration and distribution in Gigantocloa sp. bamboos, the absence of Si effect may have been related to the non-toxicity of the Cu concentration tested. * Corresponding author. E-mail addresses: collin.blanche@gmail.com, blanche.collin@uky.edu (B. Collin), doelsch@cirad.fr (E. Doelsch), keller@cerege.fr (C. Keller), Patrick.cazevieille@cirad. fr (P. Cazevieille), marie.tella@cirad.fr (M. Tella), chaurand@cerege.fr (P. Chaurand), fredericpanfili@phytorem.com (F. Panfili), jean-louis.hazemann@grenoble.cnrs.fr (J.-L. Hazemann), meunier@cerege.fr (J.-D. Meunier). 1 Present address: Department of Plant and Soil Sciences, University of Kentucky Agriculture Science Center North, 1100 s. Limestone St., Lexington, KY 40546, USA. Tel.: þ1 859 257 2467. Contents lists available at ScienceDirect Environmental Pollution journal homepage: www.elsevier.com/locate/envpol 0269-7491/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.envpol.2013.12.024 Environmental Pollution 187 (2014) 22e30