Uptake and translocation of 134Cs by maize roots as affected by heterogeneous distribution of 134Cs

Abstract

Structure-induced non-uniform water flow induces a heterogeneous distribution of surface-applied radionuclides in the soil profile. This study was conducted to assess the amount of 134Cs which can be taken up by a single root growing in an area enriched in 134Cs relative to the total amount of 134Cs that can be taken up by the whole root system growing in an area homogeneously contaminated with 134Cs. A split-root experiment was used to simulate the heterogeneous distribution of 134Cs and roots. Seedlings of maize (Zea mays L. cv Corso) were grown for 14 days in solution culture and then transferred to a two-compartment pot system, where a single root was grown in a 134Cs contaminated compartment while the rest of the root system was grown in an uncontaminated compartment. Plants with the whole root system growing in a solution contaminated with 134Cs were used as control. We tested the effect of the competition between Cs and K on the uptake and translocation of 134Cs by using two K concentrations, 0.2 and 1.05 mM. At the K concentration of the nutrient solution of 0.2 mM the single root representing 21% of the total root weight was able to take up 47% of the 134Cs taken up by the entire root system, while at 1.05 mM the single root, representing 15% of the total root weight, took up 15% of the 134Cs taken up by the entire root system. The translocation of 134Cs from the root to the shoots did not depend on the external K concentration in the nutrient solution, but it was lower in the split root treatment than in the control treatment at both K concentrations.