Fig. 5.

A schematic model of root-absorbed Fe transport in graminaceous plants based on our results and previous knowledge. In graminaceous plants, YS1 and its homologs (YSL) are responsible for Fe³⁺–MAs uptake from the soil. Fe is then transported to the xylem, and then the phloem. Although the exact location of Fe transfer from xylem to phloem remains unknown, Fe transfer may occur in the DC and/or the roots (thick black arrows). Fe is mainly translocated to the youngest leaf via phloem (thick red arrow) and partly via xylem (thin blue arrow), whereas Fe is mostly translocated to older leaves via xylem (thick blue arrow). Fe translocation to younger leaves occurs in preference to older leaves. Our study does not exclude the possibility that re-translocation of Fe from the older leaves has some contribution to the long-term Fe translocation to the youngest leaf (dotted black line and thin red arrow).