Influence of potassium supply on the release radiocesium from the roots of vine plants

The foliar uptake of radioactive cesium (134Cs) by selected leaves of grape vine plants and the subsequent redistribution within the plants was examined under controlled conditions in a greenhouse. The radionuclide was applied as chloride. The plants were grown in glass containers with nutrient solution. Samples of plants and nutrient media were analyzed throughout the growing season. Radiocesium was easily taken up through the leaf surface, transported to other plant parts and to some extent released from the roots into the growing medium. In the present study, this release was investigated in more detail. Whereas cesium reaching the soil may be bound to clay particles causing clearly reduced availability for plants, radiocesium released from the plants into a nutrient solution may be taken up again by the roots, and transported within the plants. An increased supply of potassium caused a higher release of radiocesium into the nutrient solution. From these results it becomes evident that a considerable percentage of radiocesium applied on the leaf surface may be released into the rooting medium and that this may depend on the potassium availability. Well supplied grape vine plants released more radiocesium than poorly supplied plants. However the radiocesium activity of grape vine plants grown in a nutrient solution with a high potassium content compared with that of plants grown in soil or in nutrient solution with a lower potassium content was at the end of the vegetation period not considerably lower. Therefore a potassium fertilisation is not very effective in causing a faster decontamination of the plants on the soil used.