title: Evidence for the mechanisms of zinc uptake by rice using isotope fractionation.
abstract: In an earlier study, we found that rice (Oryza sativa) grown in nutrient solution well-supplied with Zn preferentially took up light (64)Zn over (66)Zn, probably as a result of kinetic fractionation in membrane transport processes. Here, we measure isotope fractionation by rice in a submerged Zn-deficient soil with and without Zn fertilizer. We grew the same genotype as in the nutrient solution study plus low-Zn tolerant and intolerant lines from a recombinant inbred population. In contrast to the nutrient solution, in soil with Zn fertilizer we found little or heavy isotopic enrichment in the plants relative to plant-available Zn in the soil, and in soil without Zn fertilizer we found consistently heavy enrichment, particularly in the low-Zn tolerant line. These observations are only explicable by complexation of Zn by a complexing agent released from the roots and uptake of the complexed Zn by specific root transporters. We show with a mathematical model that, for realistic rates of secretion of the phytosiderophore deoxymugineic acid (DMA) by rice, and realistic parameters for the Zn-solubilizing effect of DMA in soil, solubilization and uptake by this mechanism is necessary and sufficient to account for the measured Zn uptake and the differences between genotypes.
authors.affiliation: Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, UK.
authors.forename: Tim
authors.initials: T
authors.lastname: Arnold
authors.forename: Guy J D
authors.initials: GJ
authors.lastname: Kirk
authors.forename: Matthias
authors.initials: M
authors.lastname: Wissuwa
authors.forename: Michael
authors.initials: M
authors.lastname: Frei
authors.forename: Fang-Jie
authors.initials: FJ
authors.lastname: Zhao
authors.forename: Thomas F D
authors.initials: TF
authors.lastname: Mason
authors.forename: Dominik J
authors.initials: DJ
authors.lastname: Weiss
mesh_terms: D005838:Genotype; D008962:Models, Theoretical; D012275:Oryza / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D018520:Plant Shoots / Q000254:growth & development / Q000378:metabolism; D012987:Soil; D015032:Zinc / Q000378:metabolism*; D015033:Zinc Isotopes / Q000378:metabolism
chemical_list: D012987:Soil; D015033:Zinc Isotopes; D015032:Zinc