title: Heavy metal stress in alders: Tolerance and vulnerability of the actinorhizal symbiosis.
abstract: Alders have already demonstrated their potential for the revegetation of both mining and industrial sites. These actinorhizal trees and shrubs and the actinobacteria Frankia associate in a nitrogen-fixing symbiosis which could however be negatively affected by the presence of heavy metals, and accumulate them. In our hydroponic assay with black alders, quantification of the roots and shoots metal concentrations showed that, in the absence of stress, symbiosis increases Mo and Ni root content and simultaneously decreases Mo shoot content. Interestingly, the Mo shoot content also decreases in the presence of Ni, Cu, Pb, Zn and Cd for symbiotic alders. In symbiotic alders, Pb shoot translocation was promoted in presence of Pb. On the other hand, Cd exclusion in symbiotic root tissues was observed with Pb and Cd. In the presence of symbiosis, only Cd and Pb showed translocation into aerial tissues when present in the nutrient solution. Moreover, the translocation of Ni to shoot was prevented by symbiosis in the presence of Cd, Ni and Pb. The hydroponic experiment demonstrated that alders benefit from the symbiosis, producing more biomass (total, root and shoot) than non nodulated alders in control condition, and in the presence of metals (Cu, Ni, Zn, Pb and Cd). Heavy metals did not reduce the nodule numbers (SNN), but the presence of Zn or Cd did reduce nodule allocation. Our study suggests that the Frankia-alder symbiosis is a promising (and a compatible) plant-microorganism association for the revegetation of contaminated sites, with minimal risk of metal dispersion.
authors.affiliation: Centre d'étude et de valorisation de la diversité microbienne, Département de Biologie, Université de Sherbrooke, Sherbrooke, Qc J1K 2R1, Canada.
authors.forename: Pier-Anne
authors.initials: PA
authors.lastname: Bélanger
authors.affiliation: Centre d'étude et de valorisation de la diversité microbienne, Département de Chimie, Université de Sherbrooke, Sherbrooke, Qc J1K 2R1, Canada; Princeton Environmental Institute, Princeton University, Princeton, NJ 08544, USA.
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Bellenger
authors.affiliation: Centre d'étude et de valorisation de la diversité microbienne, Département de Biologie, Université de Sherbrooke, Sherbrooke, Qc J1K 2R1, Canada. Electronic address: Sebastien.Roy@USherbrooke.ca.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Roy
mesh_terms: D029661:Alnus / Q000737:chemistry / Q000187:drug effects* / Q000382:microbiology; D018533:Biomass; D004361:Drug Tolerance; D040161:Frankia / Q000254:growth & development*; D018527:Hydroponics; D019216:Metals, Heavy / Q000633:toxicity*; D009586:Nitrogen Fixation; D018517:Plant Roots / Q000737:chemistry / Q000187:drug effects / Q000382:microbiology; D018520:Plant Shoots / Q000737:chemistry / Q000187:drug effects / Q000382:microbiology; D012989:Soil Pollutants / Q000633:toxicity*; D013559:Symbiosis / Q000187:drug effects*
chemical_list: D019216:Metals, Heavy; D012989:Soil Pollutants
keywords: Actinorhizal; Alnus glutinosa; Frankia; Heavy metal; Phytoremediation; Symbiosis