title: Plant growth responses to inorganic environmental contaminants are density-dependent: experiments with copper sulfate, barley and lettuce.
abstract: The density-dependence of terrestrial plant-plant interactions in the presence of toxins has previously been explored using biodegradable compounds. We exposed barley and lettuce to four copper concentrations at four stand densities. We hypothesized that toxin effects would decrease and Cu uptake would increase at increasing plant densities. We analyzed toxin effects by (a) comparing plant biomasses and (b) using a recent regression model that has a separate parameter for the interaction of resource competition and toxin interference. Plant response to Cu was density-dependent in both experiments. Total Cu uptake by barley increased and the dose per plant decreased as plant density increased. This study is the first to demonstrate that plant density mediates plant response to metals in soil in a predictable way. This highlights the need to explore the mechanisms for and consequences of these effects, and to integrate the use of several plant densities into standard ecotoxicological testing.
authors.affiliation: University of Helsinki, Department of Environmental Sciences, Section of Environmental Ecology, Niemenkatu 73, 15140 Lahti, Finland.
authors.forename: Mari
authors.initials: M
authors.lastname: Hansi
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Weidenhamer
authors.forename: Aki
authors.initials: A
authors.lastname: Sinkkonen
mesh_terms: D018533:Biomass; D019327:Copper Sulfate / Q000633:toxicity*; D054750:Ecotoxicology; D004784:Environmental Monitoring; D001467:Hordeum / Q000187:drug effects / Q000502:physiology*; D018545:Lactuca / Q000187:drug effects / Q000502:physiology*; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000633:toxicity*
chemical_list: D012987:Soil; D012989:Soil Pollutants; D019327:Copper Sulfate
keywords: Barley; Copper sulfate; Density–response bioassay; Lettuce; Plant density; Toxin dilution