Abstract
Soluble Fe in soil is represented by a mixture of complexes between Fe and organic ligands such as organic acids and phytosiderophores (PS). In this work we studied the mechanisms of Fe acquisition in barley plants supplied with 59Fe-PS or 59Fe-citrate (1 μM Fe, pH 7.5). Fe-sources has been supplied at the beginning (max release of PS) and at the end (basal release) of light cycle. Results show that Fe-deficient plants accumulate higher amounts of Fe from both sources, compared to the Fe-sufficient ones. The uptake rate changed during the light cycle, especially in Fe-deficient plants, reaching the highest values in the morning, and was dependent on the Fe-sources, being generally higher when Fe was supplied as Fe-PS. The pH influence on Fe uptake was evaluated in the range 5.5 - 8.0; pH increase caused a reduction in the capability of plants to take up Fe. Measurements of Fe-PS stability by LC-ICP/MS at different pHs showed that the formation of the complex is highly dependent on pH. These results highlight the importance of proton gradient not only for the release of PS and Fe-PS uptake, but also for the formation of the complex