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

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. Section Editor: R. W. Bell