title: Arsenic uptake and speciation and the effects of phosphate nutrition in hydroponically grown kikuyu grass (Pennisetum clandestinum Hochst).
abstract: BACKGROUND
  This work focuses on the accumulation and mobility properties of arsenic (As) and the effects of phosphate (P) on its movement in Pennisetum clandestinum Hochst (kikuyu grass), grown hydroponically under increasing arsenate (As(V)) concentrations. The uptake of both ions and the relative kinetics show that phosphate is an efficient competitive inhibitor of As(V) uptake. The P/As uptake rate ratios in roots indicate that P is taken up preferentially by P/As transporters. An arsenite (As(III)) efflux from roots was also found, but this decreased when the arsenate concentration in the solution exceeded 5 μM.
  
  
  METHODS
  Increases in both arsenite and arsenate concentrations in roots were observed when the arsenate concentration in the solution was increased, and the highest accumulation of As(III) in roots was found when plants were grown at 5 μM As(V). The low ratios of As accumulated in shoots compared to roots suggest limited mobility of the metalloid within Kikuyu plants.
  
  
  RESULTS
  The results indicate that arsenic resistance in kikuyu grass in conditions of moderate exposure is mainly dependent on the following factors: 1) phosphate nutrition: P is an efficient competitive inhibitor of As(V) uptake because of the higher selectivity of membrane transporters with respect to phosphate rather than arsenate; and 2) a detoxification mechanism including a reduction in both arsenate and arsenite root efflux.
  
  
  CONCLUSIONS
  The As tolerance strategy of Kikuyu limits arsenate uptake and As translocation from roots to shoots; therefore, this plant cannot be considered a viable candidate for use in the phytoextraction of arsenic from contaminated soils or water.
authors.affiliation: Department of Biotechnologies for Food and Environmental Monitoring, Mediterranea University, Feo di Vito, 89124, Reggio Calabria, 89124, Italy. mpanuccio@unirc.it
authors.forename: Maria Rosaria
authors.initials: MR
authors.lastname: Panuccio
authors.forename: Barbara
authors.initials: B
authors.lastname: Logoteta
authors.forename: Gian Maria
authors.initials: GM
authors.lastname: Beone
authors.forename: Massimo
authors.initials: M
authors.lastname: Cagnin
authors.forename: Giovanni
authors.initials: G
authors.lastname: Cacco
mesh_terms: D000222:Adaptation, Physiological; D001149:Arsenates / Q000737:chemistry / Q000378:metabolism; D001151:Arsenic / Q000737:chemistry / Q000378:metabolism*; D018053:Arsenites / Q000737:chemistry / Q000378:metabolism; D001673:Biodegradation, Environmental; D018527:Hydroponics; D031782:Pennisetum / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism* / Q000494:pharmacology*; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001149:Arsenates; D018053:Arsenites; D010710:Phosphates; D014874:Water Pollutants, Chemical; D001151:Arsenic