title: The pH strongly influences the uranium-induced effects on the photosynthetic apparatus of Arabidopsis thaliana plants.
abstract: To study the impact of environmental uranium (U) contamination, effects should be analysed at different environmentally relevant pH levels as the speciation of U, and hence its toxicity, is strongly dependent on the pH. As photosynthesis is a major energy producing process in plants intimately connected to plant growth and known to be susceptible to metal stress, the effects of different U concentrations on photosynthesis in 18-day-old Arabidopsis thaliana (Columbia ecotype) are investigated at two contrasting pH levels, pH 4.5 and pH 7.5. At pH 4.5, U is highly taken up by the roots but is poorly translocated to the shoots, while at pH 7.5, less U is taken up but the translocation is higher. The lower U concentrations in the shoots at pH 4.5 are accompanied by a more reduced leaf growth as compared to pH 7.5. In addition, U does not influence the photosynthetic machinery at pH 7.5, while an optimization of the photosynthesis takes place after U exposure at pH 4.5. As such, more of the absorbed quanta are effectively used for photosynthesis accompanied by a decreased non-photochemical quenching and an increased electron transport rate. Since the enhanced photosynthesis at pH 4.5 is accompanied by a decreased growth, we suggest that the energy produced during photosynthesis is used for defence reactions against U-induced oxidative stress rather than for growth. As such, a high discrepancy was observed between the two pH levels, with an optimized photosynthetic apparatus at pH 4.5 and almost no effects at pH 7.5.
authors.affiliation: Belgian Nuclear Research Centre (SCK•CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol, Belgium; Hasselt University, Centre for Environmental Sciences, Agoralaan Building D, 3590 Diepenbeek, Belgium. Electronic address: eline.saenen@sckcen.be.
authors.forename: Eline
authors.initials: E
authors.lastname: Saenen
authors.affiliation: Belgian Nuclear Research Centre (SCK•CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol, Belgium.
authors.forename: Nele
authors.initials: N
authors.lastname: Horemans
authors.affiliation: Belgian Nuclear Research Centre (SCK•CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol, Belgium.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Vanhoudt
authors.affiliation: Belgian Nuclear Research Centre (SCK•CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol, Belgium.
authors.forename: Hildegarde
authors.initials: H
authors.lastname: Vandenhove
authors.affiliation: Belgian Nuclear Research Centre (SCK•CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol, Belgium; Hasselt University, Centre for Environmental Sciences, Agoralaan Building D, 3590 Diepenbeek, Belgium.
authors.forename: Geert
authors.initials: G
authors.lastname: Biermans
authors.affiliation: Belgian Nuclear Research Centre (SCK•CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol, Belgium.
authors.forename: May
authors.initials: M
authors.lastname: Van Hees
authors.affiliation: Belgian Nuclear Research Centre (SCK•CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol, Belgium.
authors.forename: Jean
authors.initials: J
authors.lastname: Wannijn
authors.affiliation: Hasselt University, Centre for Environmental Sciences, Agoralaan Building D, 3590 Diepenbeek, Belgium.
authors.forename: Jaco
authors.initials: J
authors.lastname: Vangronsveld
authors.affiliation: Hasselt University, Centre for Environmental Sciences, Agoralaan Building D, 3590 Diepenbeek, Belgium.
authors.forename: Ann
authors.initials: A
authors.lastname: Cuypers
mesh_terms: D017360:Arabidopsis / Q000187:drug effects* / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D010788:Photosynthesis / Q000187:drug effects*; D018517:Plant Roots / Q000187:drug effects* / Q000378:metabolism*; D014501:Uranium / Q000494:pharmacology*
chemical_list: D014501:Uranium
keywords: Arabidopsis thaliana; Photosynthesis; Uranium; pH