Uptake and transport of radioactive cesium and strontium into strawberry plants and grapevines after leaf contamination

Radioactive strontium in the form of a carrier free aqueous solution of 85SrCl2 was taken up by the leaves of strawberry plants and grapevines at different rates. Only a limited amount was transported from the contaminated leaves into other plant organs. However no strontium was found in the fruit. These findings show that bivalent strontium is mobile in plants only to a very minor extent. In contrast, radioactive cesium applied as an aqueous solution of carrier-free 134CsCl was taken up very quickly from the leaf surface, transported from there to other plant parts and released to some extent into the soil via the roots. In our investigations strawberry fruit showed a high cesium content. The cesium content in grape berries rose during growth and decreased again in a late phase of maturation and the nuclide was partly redistributed to other plant parts. Cesium reaching the soil may interact with clay particles resulting in a very limited availability for plants. First results of investigations with grapevines in hydroculture demonstrated a close relationship between potassium supply and cesium release. The foliar uptake of radioactive strontium into plants is minor and represents therefore a negligible risk for the consumer of fruits, berries and nuts. Radioactive cesium nuclides may however reach the human food chain through the leaves of food plants. (author)