Iron‐reducing root exudates: A modified microanalytical method

Abstract

Interferences were detected in the PDTS method for the measurement of Fe‐reducing compounds exuded by plant roots into Hoagland nutrient solution. These were caused by a) excess NH₃ which is present in the ammonium acetate buffer used in the assay, which forms precipitates with the KH₂PO₄ especially when nutrient solution aliquots of larger than 2 mL are to be tested, and b) the overriding effect of autoreduction of Fe due to the very high concentration of FeCl₃ present in the assay medium. A modified method is presented whereby up to 20 mL of rooting solution can be tested and the interference due to autoreduction eliminated. Comparative measurements by the proposed and the original method show that the original method overestimates the amount of Fe‐reducing root exudates by Fe‐deficient plants by more than tenfold.