Evidence for the mechanisms of zinc uptake by rice using isotope fractionation.
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.
Arnold
Tim
T
Department of Earth Science and Engineering, Imperial College London, London SW7 2AZ, UK.
Kirk
Guy J D
GJ
Wissuwa
Matthias
M
Frei
Michael
M
Zhao
Fang-Jie
FJ
Mason
Thomas F D
TF
Weiss
Dominik J
DJ
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
D012987:Soil; D015033:Zinc Isotopes; D015032:Zinc