title: Influence of nutrient medium composition on uranium toxicity and choice of the most sensitive growth related endpoint in Lemna minor.
abstract: Uranium (U) toxicity is known to be highly dependent on U speciation and bioavailability. To assess the impact of uranium on plants, a growth inhibition test was set up in the freshwater macrophyte Lemna minor. First growth media with different compositions were tested in order to find a medium fit for testing U toxicity in L. minor. Following arguments were used for medium selection: the ability to sustain L. minor growth, a high solubility of U in the medium and a high percentage of the more toxic U-species namely UO2(2+). Based on these selection criteria a with a low phosphate concentration of 0.5 mg L(-1) and supplemented with 5 mM MES (2-(N-morpholino)ethanesulfonic acid) to ensure pH stability was chosen. This medium also showed highest U toxicity compared to the other tested media. Subsequently a full dose response curve for U was established by exposing L. minor plants to U concentrations ranging from 0.05 μM up to 150 μM for 7 days. Uranium was shown to adversely affect growth of L. minor in a dose dependent manner with EC10, EC30 and EC50 values ranging between 1.6 and 4.8 μM, 7.7-16.4 μM and 19.4-37.2 μM U, respectively, depending on the growth endpoint. Four different growth related endpoints were tested: frond area, frond number, fresh weight and dry weight. Although differences in relative growth rates and associated ECx-values calculated on different endpoints are small (maximal twofold difference), frond area is recommended to be used to measure U-induced growth effects as it is a sensitive growth endpoint and easy to measure in vivo allowing for measurements over time.
authors.affiliation: Belgian Nuclear Research Centre (SCK•CEN), Boeretang 200, B-2400, Mol, Belgium; Hasselt University, Centre for Environmental Sciences, Agoralaan gebouw D, B-3590, Diepenbeek, Belgium. Electronic address: nele.horemans@sckcen.be.
authors.forename: Nele
authors.initials: N
authors.lastname: Horemans
authors.affiliation: Belgian Nuclear Research Centre (SCK•CEN), Boeretang 200, B-2400, Mol, Belgium.
authors.forename: May
authors.initials: M
authors.lastname: Van Hees
authors.affiliation: Belgian Nuclear Research Centre (SCK•CEN), Boeretang 200, B-2400, Mol, Belgium.
authors.forename: Eline
authors.initials: E
authors.lastname: Saenen
authors.affiliation: Belgian Nuclear Research Centre (SCK•CEN), Boeretang 200, B-2400, Mol, Belgium.
authors.forename: Arne
authors.initials: A
authors.lastname: Van Hoeck
authors.affiliation: Belgian Nuclear Research Centre (SCK•CEN), Boeretang 200, B-2400, Mol, Belgium.
authors.forename: Valérie
authors.initials: V
authors.lastname: Smolders
authors.affiliation: Department of Biology, University of Antwerp (UA), Groenenborgerlaan 171, B-2020, Antwerp, Belgium.
authors.forename: Ronny
authors.initials: R
authors.lastname: Blust
authors.affiliation: Belgian Nuclear Research Centre (SCK•CEN), Boeretang 200, B-2400, Mol, Belgium.
authors.forename: Hildegarde
authors.initials: H
authors.lastname: Vandenhove
mesh_terms: D029064:Araceae / Q000254:growth & development / Q000528:radiation effects*; D002254:Carbonates / Q000737:chemistry; D004307:Dose-Response Relationship, Radiation; D006863:Hydrogen-Ion Concentration; D010710:Phosphates / Q000737:chemistry; D014501:Uranium / Q000633:toxicity*; D014875:Water Pollutants, Radioactive / Q000633:toxicity*
chemical_list: D002254:Carbonates; D010710:Phosphates; D014875:Water Pollutants, Radioactive; D014501:Uranium
keywords: Culture medium; Growth inhibition; Lemna minor; Uranium speciation; Uranium toxicity