Effect of Fe stress on utilization of Fe chelates by efficient and inefficient plant species

Abstract

Abstract Using a double labelled Fe chelate (FeEDDHA) it has been possible to show that plants can take up Fe both, as an intact Fe chelate molecule and as ionic Fe after chelate splitting. The rate of chelate splitting in the roots is determined mainly by the Fe nutritional status of the particular plant species but also by the cation exchange capacity of the roots (positive correlation). While Fe stress has no influence on the rate of chelate splitting and the uptake of Fe by Fe‐inefficient plant species (corn), in Fe‐effi‐cient species (sunflower) it brings about a dramatic increase of the rate of Fe uptake following pronounced chelate splitting. This enhanced utilization of chelated Fe by Fe‐efficient plant species under Fe stress is associated with changes in root morphology (thickening of cortical cells, additional division of rhizodermis cells, increased formation of root hairs, presence of transfer cells). Physiological changes in the roots also accompany there morphological developments (increase in proton efflux and reducing capacity, accumulation of phenols). The relevance of a proposed model to the uptake mechanism of Fe chelate including chelate transformation at the plasmalemma is discussed.