We also tested if PDMA could be a competitor for DMA, which is naturally secreted by rice plants. Figure shows the competition between DMA and PDMA for Zn II complexation when the two ligands are present at equal concentrations (molar ratio of Zn II :PDMA:DMA is 1:10:10). Under these conditions, almost all the Zn II is complexed by DMA as logK values for DMA are higher (Figure ; Table and SI Table ). These results show that competition between PDMA and DMA is unlikely to be important in soil, despite their similarity in term of structure and complexation ability. This means that PDMA may offer additional support to rice for Zn acquisition, particularly when plant DMA secretion is not sufficient to manage the nutrient deficiency.