Kinetics of caesium and potassium absorption by roots of three grass pastures and competitive effects of potassium on caesium uptake in Cynodon sp
- Grupo de Estudios Ambientales. Instituto de Matematica Aplicada San Luis. Universidad Nacional de San Luis-CONICET. Ejercito de los Andes 950 (Argentina)
- Area de Fisiologia Vegetal. Departamento de Biologia Vegetal. Facultad de Ciencias. Universidad de Malaga (Spain)
Caesium uptake by plant roots has been normally associated with the uptake of potassium as the potassium transport systems present in plants have also the capacity to transport caesium. Three grass species (Eragrostis curvula, Cynodon sp and Distichlis spicata) growing in seminatural grassland of central Argentina were selected to study their capability to incorporate Cs{sup +} (and K{sup +}) using electrophysiological techniques. Although the {sup 137}Cs soil inventory ranged between 328-730 Bq m{sup -2} in this region, no {sup 137}Cs activity was detected in these plants. However, all the species, submitted previously to K{sup +} starvation, showed the uptake of both Cs{sup +} and K{sup +} when micromolar concentrations of these cations were present in the medium. The uptake showed saturation kinetics for both cations that could be fitted to the Michelis-Menten model. K{sub M} values were smaller for K{sup +} than for Cs{sup +}, indicating a higher affinity for the first cation. The presence of increasing K{sup +} concentrations in the assay medium inhibited Cs{sup +} uptake in Cynodon sp., as expected if both cations are transported by the same transport systems. This effect is due to the competition of both ions for the union sites of the high affinity potassium transporters. In field situation, where soil concentration of Cs{sup +} is smaller than K{sup +} concentration, is then expectable that caesium activity in plants is not detectable. Nevertheless, the studied plants would have the capacity to incorporate caesium if its availability in soil solution increases. In addition, studies of Cs/K interaction can help us to understand the variability in transfer factors.
- OSTI ID:
- 21152456
- Journal Information:
- AIP Conference Proceedings, Vol. 1034, Issue 1; Conference: NRE-VIII: 8. International symposium on the natural radiation environment, Buzios, RJ (Brazil), 7-12 Oct 2007; Other Information: DOI: 10.1063/1.2991224; (c) 2008 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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