An iron chelating compound released by barley roots in response to Fe‐deficiency stress

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Abstract
The excretion of phytosiderophores by barley (Hordeum vulgare L.) has recently been documented and a major difference in the Fe‐stress response of gramineous species and dicotyledonous species proposed. However, currently used methods of quantifying and measuring phytosiderophore are tedious or require specialized equipment and a cultivar easily accessible to U.S. scientists is needed. The objectives of this study were (a) to determine if “Steptoe”; and “Europa”; (used as a control cultivar) barleys would release Fe3+ solubilizing compounds in response to Fe‐deficiency stress and (b) to develop a technique to determine the efficiency of solubilization of Fe(OH)3 by the released chelating substances. Two cultivars of barley were place under Fe‐stressed (‐Fe) and nonstressed (+Fe) conditions in modified Hoagland solutions (14 L). The solutions were periodically monitored for H+ and reductant release from the roots and plants were rated daily for chlorosis development. Periodic (6 or 7 harvests) evaluation of the release of Fe3+ solubilizing substances was performed as herein described. Neither H+ nor reductant extrusion occurred with either cultivar during Fe stress. However, Fe3+ solubilizing substances were released by both cultivars at relatively high levels under Fe‐stress conditions compared to the nonstressed plants. A convenient technique was developed to measure the release of Fe solubilizing substances released by barley roots.