Mechanism of iron uptake by plants

Abstract

Abstract. Green plants require a continuous supply of Fe as they grow, because Fe does not not move from the older to the newer leaves. Soils do not lack Fe per se, but it may not be available to plants grown in alkaline soils. Plants are classed ‘Fe‐efficient’ if they respond to Fe‐deficiency stress by inducing biochemical reactions that make Fe available in a useful form, and ‘Fe‐inefficienT’ if they do not. Iron uptake induced in response to Fe stress involves release of hydrogen ions and reductants by the root. The lowered pH and presence of reductant at the root zone, along with reduction of Fe3+ to Fe2+ at the root surface, enables Fe2+ to be taken up primarily through the young lateral roots. Ferrous iron is present throughout the protozylem and may or may not have entered the root by a carrier. The root‐absorbed Fe2+ is oxidized to Fe3+ at the junction of the protoxylem and the metaxylem, chelated by citrate, and then transported in the metaxylem to the plant top. In the plant, the chemical reactions injuced by Fe‐deficiency stress may affect nitrate reductase activity, use of Fe from Fe3+ phosphate and chelating agents, and tolerance to heavy metals. An efficient mechanism for Fe uptake in roots appears to be important for the efficient use of Fe in plant tops.