The focus of this thesis is physicochemical characterisation of Zn complex with a natural phytosiderophore ligand – 2’-deoxymugineic acids (DMA), in light of its possible role in the root Zn uptake in staple crop species, such as rice. Mechanisms behind efficient Zn acquisition in rice cultivars are not yet clearly identified. Yet, this information is vital for the progress of biofortification programs of staple food crops.
The work shown in this thesis examines the stability of the [Zn(DMA)] complex in view of the required traits for the fulfillment of the phytosiderophore role. To this end, the ligand in question was synthesised in laboratory conditions. Subsequent tests have shown that the Zn binding affinity of DMA is substantial in comparison to the other rhizosphere present organic molecules. Therefore, solubilisation by DMA is a promising Zn acquisition mechanism in plants.
The studies following this investigate stable isotope partitioning upon Zn complexation with DMA by means of experiments, as well as by using computational chemistry calculation methods. Both methods yielded the same conclusion: Zn complexation by DMA favours the heavy 66Zn isotope (∆66Zn ~0.3 ‰), and hence, can introduce a significant isotopic fractionation into the environment.
The results of a study on field grown rice are also presented. In this study heavy isotopic enrichment is demonstrated under Zn-deficient conditions in two rice genotypes differing in their susceptibility to Zn-deficient soils; where A69-1 and IR26 are low-Zn tolerant and sensitive cultivars used, respectively. The heavy fractionation factors ((∆66Zn) 0.21 ‰ and ~0.30 ‰ for the tolerant and sensitive rice, respectively) are consistent with Zn solubilisation and uptake by phytosiderophore ligands, and the magnitude of the measured factors corresponds well with the values identified in the preceding experimental and theoretical studies.