Effect of sodium on iron absorption, translocation and allocation in halophilic Amaranthaceae species

In arid regions, alkaline conditions resulting from soil sodification make iron unavailable, causing plants to suffer from salt-alkali stress. We hypothesized that halophilic species possess an exceptional iron uptake mechanism involving Na. Here, we investigated the effects of medium pH (acidic or neutral), amounts of iron (0.358 μM or 35.8 μM) and NaCl (5 or 100 mM) on Fe uptake, translocation, and allocation in salt tolerant Mexican tea (Dysphania ambrosioides L.), halophilic mesophyte Swiss chard (Beta vulgaris L. spp. cicla), and euhalophyte romeritos (Suaeda edulis Flores Olv. & Noguez) for 6 days. At this stage, when growth differences were not yet observed, the halophilic Swiss chard and romeritos exhibited a tendency for increased iron uptake under high NaCl, with a obviously increase in iron translocation to the shoots. Although transpiration and ferric chelate reductase activity were not increased by high NaCl. But medium pH was led toward the acidic range by high NaCl. Iron absorption was not greater in acidic medium condition compared to neutral condition, so low pH itself does not enhance iron uptake. It was concluded that an exposure to the high NaCl led to a large influx of Na into to roots which enhanced H⁺ motive force to increase Fe uptake. This finding may explain the reason that the grown of these species in saline-alkali soil.