title: Multiple mechanisms of heavy metal tolerance are differentially expressed in ecotypes of Artemisia fragrans.
abstract: Artemisia fragrans is a plant species with ability of growing on heavy metal-polluted soils. Ecotypes of this species naturally growing in polluted areas can accumulate and tolerate different amounts of heavy metals (HM), depending on soil contamination level at their origin. Heavy metal tolerance of various ecotypes collected from contaminated (AP, SP) and non-contaminated (BG) sites was compared by cultivation on a highly HM-contaminated river sediment and a non-contaminated agricultural control soil. Tissue-specific HM distribution was analyzed by laser ablation-inductively-coupled plasma-mass spectroscopy (LA-ICP-MS) and photosynthetic activity by non-invasive monitoring of chlorophyll fluorescence. Plant-mineral analysis did not reveal ecotype-differences in concentrations of Cd, Zn, Cu in shoots of Artemisia plants, suggesting no differential expression of root uptake or root to shoot translocation of HM. There was also no detectable rhizosphere effect on HM concentrations on the contaminated soil. However, despite high soil contaminations, all ecotypes accumulated Zn only in the concentration range of generally reported for normal growth of plants, while Cu and Cd concentrations were close to or even higher than the toxicity level for most plants. As a visible symptom of differences in HM tolerance, only the AP ecotype was able to enter the generative phase to complete its life cycle. Analysis of tissue-specific metal distribution revealed significantly lower concentrations of Cd in the leaf mesophyll of this ecotype, accumulating Cd mainly in the leaf petioles. A similar mesophyll exclusion was detectable also for Cu, although not associated with preferential accumulation in the leaf petioles. However, high mesophyll concentrations of Cd and Cu in the SP and BG ecotypes were associated with disturbances of the photosynthetic activity. The findings demonstrate differential expression of HM exclusion strategies in Artemisia ecotypes and suggest Cd and Cu exclusion from the photosynthetically active tissues as a major tolerance mechanism of the AP ecotype.
authors.affiliation: Institute of Botany of Azerbaijan National Academy of Sciences, Badamdar Highway, 40, AZ1004, Baku, Azerbaijan. Electronic address: hh.esmal@hotmail.com.
authors.forename: Esmira
authors.initials: E
authors.lastname: Alirzayeva
authors.affiliation: Institute of Crop Science (340h), University of Hohenheim, Fruwirthstr., 20, D-70599, Stuttgart, Germany. Electronic address: guenter.neumann@uni-hohenheim.de.
authors.forename: Gunter
authors.initials: G
authors.lastname: Neumann
authors.affiliation: Institute for Plant Nutrition, Leibniz University of Hannover, Herrenhaeuser Str. 2, 30419, Hannover, Germany. Electronic address: horst@pflern.uni-hannover.de.
authors.forename: Walter
authors.initials: W
authors.lastname: Horst
authors.affiliation: Molecular Plant Biology, University of Turku, FI-20014, Turku, Finland. Electronic address: allahve@utu.fi.
authors.forename: Yagut
authors.initials: Y
authors.lastname: Allahverdiyeva
authors.affiliation: Institute for Plant Nutrition, Leibniz University of Hannover, Herrenhaeuser Str. 2, 30419, Hannover, Germany. Electronic address: specht@pflern.uni-hannover.de.
authors.forename: Andre
authors.initials: A
authors.lastname: Specht
authors.affiliation: Institute of Botany of Azerbaijan National Academy of Sciences, Badamdar Highway, 40, AZ1004, Baku, Azerbaijan. Electronic address: vm_alizade@yahoo.com.
authors.forename: Valida
authors.initials: V
authors.lastname: Alizade
mesh_terms: D019306:Artemisia / Q000187:drug effects* / Q000378:metabolism; D001673:Biodegradation, Environmental; D004361:Drug Tolerance; D060146:Ecotype; D019216:Metals, Heavy / Q000032:analysis / Q000378:metabolism / Q000633:toxicity*; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D058441:Rhizosphere; D012989:Soil Pollutants / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity*
chemical_list: D019216:Metals, Heavy; D012989:Soil Pollutants
keywords: Artemisia ecotypes; Heavy metals; Metal compartmentation; Photosynthetic apparatus; Plant tolerance