title: Early responses to cadmium of two poplar clones that differ in stress tolerance.
abstract: Soil cadmium (Cd) contamination is becoming a matter of great global concern. The identification of plants differentially sensitive to Cd excess is of interest for the selection of genotype adaptive to grow and develop in polluted areas and capable of ameliorating or reducing the negative environmental effects of this toxic metal. The two poplar clones I-214 (Populus×canadensis) and Eridano (Populus deltoides×maximowiczii) are, respectively, tolerant and sensitive to ozone (O3) exposure. Because stress tolerance is mediated by an array of overlapping defence mechanisms, we tested the hypothesis that these two clones differently sensitive to O3 stress factor also exhibit different tolerance to Cd. With this purpose, an outdoor pot experiment was designed to study the responses of I-214 and Eridano to the distribution of different Cd solutions enriched with CdCl2 (0, 50 and 150μM) for 35 days. Changes in leaf area, biomass allocation and Cd uptake, photosynthesis, chlorophyll fluorescence, leaf concentration of nutrients and pigments, hydrogen peroxide (H2O2) and nitric oxide (NO) production and thiol compounds were investigated. The two poplar clones showed similar sensitivity to excess Cd in terms of biomass production, photosynthesis activity and Cd accumulation, though physiological and biochemical traits revealed different defence strategies. In particular, Eridano maintained in any Cd treatment the number of its constitutively wider blade leaves, while the number of I-214 leaves (with lower size) was reduced. H2O2 increased 4.5- and 13-fold in I-214 leaves after the lowest (L) and highest (H) Cd treatments, respectively, revealing the induction of oxidative burst. NO, constitutively higher in I-214 than Eridano, progressively increased in both clones with the enhancement of Cd concentration in the substrate. I-214 showed a more elevated antioxidative capacity (GSH/GSSG) and higher photochemical efficiency of PSII (Fv/Fm) and de-epoxidation degree of xantophylls-cycle (DEPS). The glutathione pool was not affected by Cd treatment in both clones, while non-protein thiols and phytochelatins were reduced at L Cd treatment in I-214. Overall, these two clones presented high adaptability to Cd stress and are both suitable to develop and growth in environments contaminated with this metal, thus being promising for their potential use in phytoremediation programmes.
authors.affiliation: BioLabs, Life Sciences Institute, Scuola Superiore Sant'Anna, Piazza Martiri della Libertà 33, I-56127 Pisa, Italy. Electronic address: daniela.dibaccio@ibaf.cnr.it.
authors.forename: Daniela
authors.initials: D
authors.lastname: Di Baccio
authors.affiliation: Department of Crop Biology, University of Pisa, Via del Borghetto, 80, I-56124 Pisa, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Castagna
authors.affiliation: Department of Biosciences and Territory, University of Molise, Contrada Fonte Lappone, I-86090 Pesche, Italy; The EFI Project Centre on Mountain Forests (MOUNTFOR), Via Edmund Mach 1, I-38010 San Michele all'Adige, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Tognetti
authors.affiliation: Department of Crop Biology, University of Pisa, Via del Borghetto, 80, I-56124 Pisa, Italy.
authors.forename: Annamaria
authors.initials: A
authors.lastname: Ranieri
authors.affiliation: BioLabs, Life Sciences Institute, Scuola Superiore Sant'Anna, Piazza Martiri della Libertà 33, I-56127 Pisa, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Sebastiani
mesh_terms: D002104:Cadmium / Q000378:metabolism / Q000633:toxicity*; D002734:Chlorophyll / Q000378:metabolism; D005453:Fluorescence; D006824:Hybridization, Genetic; D006861:Hydrogen Peroxide / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D010788:Photosynthesis; D018515:Plant Leaves / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D032107:Populus / Q000235:genetics / Q000502:physiology*; D013312:Stress, Physiological
chemical_list: D002104:Cadmium; D002734:Chlorophyll; D009569:Nitric Oxide; D006861:Hydrogen Peroxide
keywords: Co-tolerance; Glutathione; Hydrogen peroxide; Nitric oxide; Photosynthesis