Several studies proposed that under Zn II -deficiency conditions, rice plants exude organic ligands able to complex the insoluble Zn II from the soil matrix. This follows the so-called Strategy II mechanism, widely studied for the acquisition of insoluble Fe III in graminaceous plants. These ligands are part of the mugineic acid family (MAs) commonly known as phytosiderophores. MAs are all multidentate amino acids containing three carboxylic acid groups and one azetidine ring able to bind metal ions forming water-soluble octahedral complexes . The main phytosiderophore secreted by rice is 2'-deoxymugineic acid (DMA). Based on this, Suzuki et al. developed a synthetic analogue to the DMA ligand, proline-2′-deoxymugineic acid (PDMA), which has analogous coordinating abilities to DMA, but it is easier to synthesise and more resistant to microbial decomposition. Therefore it was proposed that it could be used as fertilizer to increase the uptake of iron in Fe-deficient calcareous soil (pH ~ 9) (Figure ). The key difference between the two polydentate ligands is the substitution of the four-membered azetidine ring in DMA to a five-membered ring in PDMA, improving the resistance to biodegradation and reducing the production costs . In this context, fertilization with PDMA could potentially increase the uptake of Zn II in rice under soil deficiency conditions, as is schematically illustrated in Figure . This proposed uptake mechanism is supported by Yamagata's previous work where it was demonstrated that the carboxyl and amino group of PDMA are recognised by yellow stripe 1 (YS1) family transporter, in analogous manner to the recognition of the naturally occurring DMA.