Fe-deficiency increases Cu acquisition by wheat cropped in a Cu-contaminated vineyard soil

This work evaluated the influence of iron deficiency and phytosiderophore exudation on the acquisition of copper by two bread wheat (Triticum aestivum) genotypes and ('Aroona' and 'Songlen') grown in a calcareous vineyard soil, which had been contaminated by repeated applications of copper fungicides. A pot experiment was designed with a cropping device that enabled an easy access to shoots, roots and rhizosphere soil. Before being placed in contact with the soil, wheat seedlings had been subjected to, or not subjected to, either zinc or iron starvation in order to stimulate the release of phytosiderophores. Under zinc starvation, the zinc-efficient genotype ('Aroona') acquired more soil copper. By contrast, iron starvation resulted in an enhanced release of phytosiderophores in both genotypes (before being grown on the soil), in elevated copper concentrations in shoots and roots and in a significantly increased acquisition of copper by wheat. Iron deficiency thus resulted in elevated acquisition of copper from the copper-contaminated soil, possibly through enhanced phytosiderophore release. Phytotoxic concentrations were, however, not attained in wheat shoots, as a major proportion of acquired copper accumulated in the roots.