Copper uptake and translocation by rapeseed and sunflower under the influence of chelators and interfering ions. [Doctoral dissertation] | Usvajanje i translokacija bakra pod uticajem helatora i smetajućih jona kod uljane repice i suncokreta. Doktorska disertacija

The paper analyzed the effects of the chelators EDTA (ethylendiaminetetraacetic acid) and EDDS (ethylenediaminedisuccinic acid) on the uptake and translocation of Cu2+ into the above-ground parts of rapeseed and sunflower plants grown in a calcareous soil moderately contaminated by copper. We also investigated how the interfering ions Fe3+, Ca2+, Mn2+, Zn2+ and Mg2+ from the soil influenced the bonding of copper into complexes with EDTA and EDDS and then copper uptake and translocation in the plant. We monitored the uptake of copper and the interfering ions into the root and the above-ground parts of the rapeseed and sunflower plants as affected by the kind and dose of the chelator being applied. It was determined that the use of EDDS produced a greater increase in copper uptake and translocation in the crops being studied as compared to when EDTA was used. The largest increase was recorded when EDDS was applied at the rates of 4.8 and 4+4 mmol/kg. The Cu concentrations in the above-ground plant parts were significantly lower following the application of EDTA as compared to the application of EDDS at the same concentration. The increases in Cu uptake by the above-ground plant were significantly lower in sunflower than in rapeseed in the same treatments. Laboratory experiments were used to investigate the effects of different EDDS and EDTA doses on copper mobility in the soil. We also investigated to what extent interfering ions in the soil affected the complexation of copper. It was determined that only some forms of copper were capable of forming complexes with EDDS and EDTA. There were most notably Cu found in the soil solution and Cu bound to Mn and Fe oxides. Complexation between these ligands and Cu bound to organic matter and mineral clays, on the other hand, was very poor. It was determined that the efficiency of Cu mobilization in the soil was higher when using EDDS than when using EDTA. The significant difference in the efficiency of complexation cannot be explained by the stability constants of the Cu-EDDS and Cu-EDTA complexes, because the values of these constants were very close. Instead, it is attributable to the presence of the interfering ions, which compete with Cu for the formation of complexes to varying degrees. The greatest interference comes from Ca, especially when Ca is found in the soil in the form of the Ca2+ ion.