title: No evidence for competition between arsenate and phosphate for uptake from soil by medic or barley.
abstract: We investigated the effects of phosphorus (P) supply on the uptake and toxicity of arsenate (As(V)) in two plant species (Medicago truncatula and Hordeum vulgare) grown in soil/sand mixes. Our initial hypothesis was that competition between phosphate (Pi) and As(V) for uptake would be observed, and that this would be the basis for the 'protective' effect of P with respect to As toxicity, as shown in solution culture. Addition of P to the soil/sand mixes did not have major effects on water extractable As, or vice versa. We observed that toxic effects of As(V) on plant growth were ameliorated by increased P in both plant species. However, we found no evidence that increased P supply reduced specific uptake of As(V) on a molar basis, so that competition with Pi could not be the basis for the effect. A more complex mechanism of protection is indicated which might relate to different Pi transport systems being expressed at different P levels.
authors.affiliation: Soil and Land Systems, School of Earth and Environmental Sciences, The University of Adelaide, Adelaide, South Australia, 5005, Australia. helle.christophersen@adelaide.edu.au
authors.forename: H M
authors.initials: HM
authors.lastname: Christophersen
authors.forename: S E
authors.initials: SE
authors.lastname: Smith
authors.forename: S
authors.initials: S
authors.lastname: Pope
authors.forename: F A
authors.initials: FA
authors.lastname: Smith
mesh_terms: D001149:Arsenates / Q000378:metabolism* / Q000633:toxicity*; D001467:Hordeum / Q000254:growth & development / Q000378:metabolism*; D046913:Medicago truncatula / Q000254:growth & development / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D012989:Soil Pollutants / Q000378:metabolism*
chemical_list: D001149:Arsenates; D010710:Phosphates; D012989:Soil Pollutants; C025657:arsenic acid