INFLUENCE OF CHELATING-AGENTS ON PLANT UPTAKE OF CR-51, PB-210 AND PO-210

Plant uptake of radio-labelled ionic and EDTA-, EDDHA- and DTPA-chelated chromium, lead and polonium was examined in nutrient solution and in an Ultisol and a Vertisol. Nutrient culture studies revealed a marked enhancement in uptake and translocation of chelated Cr-51 in beans (Phaseolus vulgaris L.); Cr-51-DTPA was most effective followed by Cr-51-EDTA and Cr-51-EDDHA. No significant differences were observed between chelated Pb-210 complexes and Pb-210(NO3)(2). However, Po-210-DTPA and Po-210-EDDHA significantly increased the shoot uptake of Po-210 in comparison to Po-210(NO3)(4). A two fold increase in transport index for Cr-51 and Po-210 was observed with chelates compared to ionic forms. Results from soil-plant studies indicated Cr-51 uptake by maize (Zea mays L.) plants, one to two orders of magnitude higher from both the Vertisol and the Ultisol, when Cr-51 was added as Cr-51-EDTA compared to ionic forms. The DTPA complexes of Pb-210 and Po-210 did not contribute significantly to plant uptake of Pb-210 in both soil types and of Po-210 in Ultisol. In contrast, Po-210 uptake was significantly enhanced from Po-210-DTPA compared to ionic Po-210(NO3)(4) in the Vertisol.