title: Differences in U root-to-shoot translocation between plant species explained by U distribution in roots.
abstract: Accumulation and distribution of uranium in roots and shoots of four plants species differing in their cation exchange capacity of roots (CECR) was investigated. After exposure in hydroponics for seven days to 100 micromol U L(-1), distribution of uranium in roots was investigated through chemical extraction of roots. Higher U concentrations were measured in roots of dicots which showed a higher CECR than monocot species. Chemical extractions indicated that uranium is mostly located in the apoplasm of roots of monocots but that it is predominantly located in the symplasm of roots of dicots. Translocation of U to shoot was not significantly affected by the CECR or distribution of U between symplasm and apoplasm. Distribution of uranium in roots was investigated through chemical extraction of roots for all species. Additionally, longitudinal and radial distribution of U in roots of maize and Indian mustard, respectively showing the lowest and the highest translocation, was studied following X-ray fluorescence (XRF) analysis of specific root sections. Chemical analysis and XRF analysis of roots of maize and Indian mustard clearly indicated a higher longitudinal and radial transport of uranium in roots of Indian mustard than in roots of maize, where uranium mostly accumulated in root tips. These results showed that even if CECR could partly explain U accumulation in roots, other mechanisms like radial and longitudinal transport are implied in the translocation of U to the shoot.
authors.affiliation: Belgium Nuclear Research Centre (SCK.CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol, Belgium.
authors.forename: Anne
authors.initials: A
authors.lastname: Straczek
authors.forename: Lise
authors.initials: L
authors.lastname: Duquene
authors.forename: Dariusz
authors.initials: D
authors.lastname: Wegrzynek
authors.forename: Ernesto
authors.initials: E
authors.lastname: Chinea-Cano
authors.forename: Jean
authors.initials: J
authors.lastname: Wannijn
authors.forename: Jacques
authors.initials: J
authors.lastname: Navez
authors.forename: Hildegarde
authors.initials: H
authors.lastname: Vandenhove
mesh_terms: D018533:Biomass; D002473:Cell Wall / Q000378:metabolism; D018548:Cotyledon / Q000378:metabolism; D004307:Dose-Response Relationship, Radiation; D009149:Mustard Plant / Q000378:metabolism; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism*; D018520:Plant Shoots / Q000378:metabolism*; D012639:Seeds / Q000378:metabolism; D014908:Triticum / Q000378:metabolism; D014501:Uranium / Q000378:metabolism*; D003313:Zea mays / Q000378:metabolism
chemical_list: D014501:Uranium