Figure 7.

The Fe acquisition in rice roots grown in nutrient solution as affected by Si supply. Without Si supply, the Fe flux into the apoplast of the cortex is not severely restricted by CB in the exodermis. In the apoplast of the cortex Fe binds to excreted DMA and is taken up into the cortex cells and passes the endodermis symplastically into the xylem. Silicon supply induces the CB formation in the exodermis and hampers the flux of Fe into the apoplastic space where less Fe can be bound to DMA resulting in a reduced symplastic flux into the xylem. Abbreviations are rh: rhizodermis, ex: exodermis, sc: sclerenchyma, CB: Casparian band, c: cortex, ae: aerenchyma, ap: apoplast, en: endodermis, xy: xylem. Red and blue lines indicate apoplastic and symplastic flux, respectively.