Plants acquire micronutrients such as iron (Fe), zinc (Zn), manganese, or copper from soil. These micronutrients are often not readily available and they need to be mobilized to the proper free ionic form in order to be taken up by plant roots. Perhaps the only exception to this is the uptake of Fe by grasses, which have evolved a so-called strategy II uptake mechanism that involves the secretion of mugineic acid (MA)-family phytosiderophores to chelate Fe(III). These plants then take up the chelated Fe(III)-siderophore complexes. Most other plant species use strategy I for Fe uptake, which depends on the reduction of Fe(III) to Fe(II) and uptake through Fe2+ transporters. Because strategy II is less pH dependent than strategy I, it offers an evolutionary advance to grasses, especially when grown on calcareous soils (Römheld and Marschner, 1986).
- metal hyperaccumulation