title: Metallophyte status of violets of the section Melanium.
abstract: Violets from metal-enriched soils have controversially been described as both heavy-metal accumulators and excluders in the literature. The present study solves the issue for violets of the section Melanium (zinc violets, Viola lutea ssp. calaminaria and V. lutea ssp. westfalica; hartsease or wild pansy, Viola tricolor; and mountain pansy, V. lutea). The aims were to determine the concentrations of heavy metals in the soil and in the roots and shoots of field-collected plants, to evaluate the potential impact of colonisation by arbuscular mycorrhizal fungi on heavy-metal concentrations in the plant tissues, and to quantitatively define the localisation of the elements in root cross-sections. When these violets grow in low-metal soils, higher concentrations of the heavy metals were found in the roots and shoots than in the soil, whereas the opposite was seen in samples from high-metal soils. Under all field conditions examined, the roots of all of these species were colonised by arbuscular mycorrhizal fungi. However, V. tricolor was marginally colonised when the concentrations of Zn and P were higher in the soil. Determination of the spatial distribution of the elements in root cross-sections of these violets indicates tissue-specific deposition of elements within the vascular tissue, the cortex, and the rhizodermis. These data indicate that violets of the section Melanium are heavy-metal excluders.
authors.affiliation: Botanical Institute, University of Cologne, Zülpicher Str. 47b, D-50674 Cologne, Germany. Electronic address: hermann.bothe@uni-koeln.de.
authors.forename: Bothe
authors.initials: B
authors.lastname: Hermann
authors.forename: Vogel-Mikuš
authors.initials: VM
authors.lastname: Katarina
authors.forename: Pongrac
authors.initials: P
authors.lastname: Paula
authors.forename: Likar
authors.initials: L
authors.lastname: Matevž
authors.forename: Stepic
authors.initials: S
authors.lastname: Neva
authors.forename: Pelicon
authors.initials: P
authors.lastname: Primož
authors.forename: Vavpetič
authors.initials: V
authors.lastname: Primož
authors.forename: Jeromel
authors.initials: J
authors.lastname: Luka
authors.forename: Regvar
authors.initials: R
authors.lastname: Marjana
mesh_terms: D001673:Biodegradation, Environmental; D019216:Metals, Heavy / Q000032:analysis / Q000378:metabolism* / Q000633:toxicity; D038821:Mycorrhizae / Q000502:physiology; D018517:Plant Roots / Q000187:drug effects / Q000382:microbiology / Q000502:physiology; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis / Q000378:metabolism* / Q000633:toxicity; D032413:Viola / Q000187:drug effects / Q000382:microbiology / Q000502:physiology*
chemical_list: D019216:Metals, Heavy; D012987:Soil; D012989:Soil Pollutants
keywords: Arbuscular mycorrhiza; Element localisation; Heavy-metal exclusion; Metallophytes; Micro-PIXE; Viola species