Hydrolysis of riboflavins in root exudates under iron deficiency and alkaline stress.

Riboflavins are secreted under iron deficiency as a part of the iron acquisition Strategy I, mainly when the external pH is acidic. In plants growing under Fe-deficiency and alkaline conditions, riboflavins have been reported to accumulate inside the roots, with very low or negligible secretion. However, the fact that riboflavins may undergo hydrolysis under alkaline conditions has been so far disregarded.

Supramolecular Arrangement of Lignosulfonate-Based Iron Heteromolecular Complexes and Consequences of Their Interaction with Ca at Alkaline pH and Fe Plant Root Uptake Mechanisms.

Previous studies have shown that natural heteromolecular complexes might be an alternative to synthetic chelates to correct iron (Fe) deficiency. To investigate the mechanism of action of these complexes, we have studied their interaction with Ca at alkaline pH, Fe-binding stability, Fe-root uptake in cucumber, and chemical structure using molecular modeling. The results show that a heteromolecular Fe complex including citric acid and lignosulfonate as binding ligands (Ls-Cit) forms a supramolecular system in solution with iron citrate interacting with the hydrophobic inner core of the lignosulfonate system.