Cadmium allocation to grains depends on sulfur nutrition in durum wheat

The aim of this study was to determine if the allocation of cadmium (Cd) to grains depends on sulfur (S) nutrition in durum wheat. Durum wheat was grown in semi-hydroponics with 100 nM Cd (Cd+) or at a background concentration of Cd (Cd-). Starting from stem elongation, the plants exposed to 100 nM Cd received a standard supply of S (S100), a reduced supply of S (S20) or were subjected to S deprivation (S0). Plants were sampled at the early milk development stage (Z71) and the early ripening stage (Z91) to assess differences in plant growth, Cd uptake and partitioning among organs, as well as net remobilization of Cd in the different treatments. Durum wheat growth was not affected by exposure to 100 nM Cd, and the root-to-shoot translocation of Cd was more restricted in the Cd + treatment than in the Cd-treatment. Reducing or stopping the supply of S did not affect durum wheat growth but enhanced S remobilization from almost all plant parts, including the roots. Stopping the supply of S resulted in a 35 % increase in the concentration of Cd in the grains. The proportional decrease in the concentrations of S and Cd in the roots of S-deficient plants between Z71 and Z91 suggests that Cd remobilization is associated with S remobilization in the roots of durum wheat. Sulfur deficiency promoted Cd accumulation in durum wheat grains likely due to enhanced remobilization of S and Cd in the roots of S-deficient plants.