title: Cadmium toxicity investigated at the physiological and biophysical levels under environmentally relevant conditions using the aquatic model plant Ceratophyllum demersum.
abstract: Cadmium (Cd) is an important environmental pollutant and is poisonous to most organisms. We aimed to unravel the mechanisms of Cd toxicity in the model water plant Ceratophyllum demersum exposed to low (nM) concentrations of Cd as are present in nature. Experiments were conducted under environmentally relevant conditions, including nature-like light and temperature cycles, and a low biomass to water ratio. We measured chlorophyll (Chl) fluorescence kinetics, oxygen exchange, the concentrations of reactive oxygen species and pigments, metal binding to proteins, and the accumulation of starch and metals. The inhibition threshold concentration for most parameters was 20 nM. Below this concentration, hardly any stress symptoms were observed. The first site of inhibition was photosynthetic light reactions (the maximal quantum yield of photosystem II (PSII) reaction centre measured as Fv /Fm , light-acclimated PSII activity ΦPSII , and total Chl). Trimers of the PSII light-harvesting complexes (LHCIIs) decreased more than LHC monomers and detection of Cd in the monomers suggested replacement of magnesium (Mg) by Cd in the Chl molecules. As a consequence of dysfunctional photosynthesis and energy dissipation, reactive oxygen species (superoxide and hydrogen peroxide) appeared. Cadmium had negative effects on macrophytes at much lower concentrations than reported previously, emphasizing the importance of studies applying environmentally relevant conditions. A chain of inhibition events could be established.
authors: Department of Plant Biophysics and Biochemistry, Institute of Plant Molecular Biology, Biology Centre of the CAS, Branišovská 31/1160, České Budějovice, CZ-37005, Czech Republic.|Department of Biology, University of Konstanz, Konstanz, D-78457, Germany.
authors: Elisa
authors: E
authors: Andresen
authors: Department of Biology, University of Konstanz, Konstanz, D-78457, Germany.
authors: Sophie
authors: S
authors: Kappel
authors: Department of Analytical Chemistry, UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, Leipzig, D-04318, Germany.
authors: Hans-Joachim
authors: HJ
authors: Stärk
authors: Department of Biology, University of Konstanz, Konstanz, D-78457, Germany.
authors: Ulrike
authors: U
authors: Riegger
authors: Department of Hydrochemistry and Ecosystem Modelling, Institute of Hydrobiology, Biology Centre of the CAS, Na Sádkách 7, České Budějovice, CZ-37005, Czech Republic.|Department of Ecosystem Biology, Faculty of Science, University of South Bohemia, Branišovská 1760, České Budějovice, CZ-37005, Czech Republic.
authors: Jakub
authors: J
authors: Borovec
authors: Department of Analytical Chemistry, UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, Leipzig, D-04318, Germany.
authors: Jürgen
authors: J
authors: Mattusch
authors: Institute of Pharmacy, Martin-Luther-Universität Halle-Wittenberg, Wolfgang-Langenbeck-Str. 4, Halle (Saale), D-06120, Germany.
authors: Andrea
authors: A
authors: Heinz
authors: Institute of Pharmacy, Martin-Luther-Universität Halle-Wittenberg, Wolfgang-Langenbeck-Str. 4, Halle (Saale), D-06120, Germany.
authors: Christian E H
authors: CE
authors: Schmelzer
authors: Institute of Geology of the CAS, Rozvojová 269, Praha 6 - Lysolaje, CZ-16500, Czech Republic.
authors: Šárka
authors: Š
authors: Matoušková
authors: Department of Chemistry, The University of Chicago, GCIS E 319A, 929 E. 57th St., Chicago, IL, 60637, USA.
authors: Bryan
authors: B
authors: Dickinson
authors: Department of Plant Biophysics and Biochemistry, Institute of Plant Molecular Biology, Biology Centre of the CAS, Branišovská 31/1160, České Budějovice, CZ-37005, Czech Republic.|Department of Biology, University of Konstanz, Konstanz, D-78457, Germany.|Faculty of Biological Science, University of South Bohemia, Branišovská 31/1160, České Budějovice, CZ-37005, Czech Republic.
authors: Hendrik
authors: H
authors: Küpper
mesh_terms: D002104:Cadmium / Q000633:toxicity*; D006861:Hydrogen Peroxide / Q000378:metabolism; D008027:Light; D019684:Magnoliopsida / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism
chemical_list: D045332:Photosystem II Protein Complex; D017382:Reactive Oxygen Species; D002104:Cadmium; D013481:Superoxides; D006861:Hydrogen Peroxide
keywords: Cadmium (Cd); Ceratophyllum demersum; environmentally relevant; light-harvesting complexes (LHCs); macrophyte; toxic metals; toxicity