Cesium transfer to millet and mustard as a function of Cs availability in soils

International audience137Cs is one of the most persistent radioactive contaminant in soil after a nuclear accident. It can be taken up by plants and enter the human food chain generating major hazard for population health. Although a huge literature have highlighted the role of different processes involved in Cs uptake by plants, there is still no simple way to predict its transfer for a specific plant from a particular soil. The objective of this study is to assess the assumption that concentration ratio (CR) of Cs can be predicted from one plant taxon knowing the CR of another taxon taken as reference whatever the soils on which plants are grown. A series of plant/soil Cs transfer experiments were performed on Rhizotest using three soils with contrasted Cs retention capacity and two plants (millet and mustard) with contrasted Cs uptake capacity based on their phylogeny. Results highlighted a different behaviour than that expected, with CR of mustard being either higher, equal or lower than the one of millet depending on the soils. These results can be put in regards to the large variation of the CR of millet on these 3 soils (3 orders of magnitude). Parameters linked to plant physiology (growth, water use efficiency, potassium (K) uptake and distribution in planta) or K level in soil solution failed to explain the relative behaviour of millet compared to mustard as a function of soils. However considering Cs availability in soils and defining a new CR based on the amount of Cs available in the soil (CRavail) permits to decrease the range of variation of CR for a given plant between the soils