Abstract
An amaranthaceous halophyte, dwarf glasswort (Salicornia bigelovii), absorbs Fe and shows satisfactory growth under high pH. In this study, we investigated the strategy of Fe absorption by dwarf glasswort at high pH. In dwarf glasswort, there was no difference in the Fe concentration of shoots at pH 5.0 and pH 8.5. At pH 8.5 condition, dwarf glasswort drastically decreased the pH of the solution, and it absorbed more cations than anions for a short period. The observed acidification might have been due to secretion of protons to the rhizosphere due to absorption of Na. In contrast, the ability of spinach to decrease the solution pH was lower than that of dwarf
glasswort. At pH 8.5, the ferric reductase (FR) activity of spinach decreased. However, dwarf glasswort showed similar FR activity at pH 5.0 and 8.5. It is possible that dwarf glasswort can maintain high FR activity at high pH. Thus, dwarf glasswort not only decreases external pH by secreting protons to make Fe available but it can also absorb Fe due to having a FR tolerant to high pH.
