The exudation of organic acids by pigeonpea roots for solubilizing iron- and aluminum-bound phosphorus

Abstract

We determined the P-solubilizing agents in root exudates from pigeonpea, and studied factors controlling the exudation. Pigeonpea plants were grown in sand with 3 levels of P application. The dry weight and P concentration of the plants increased with increasing P application, and the plants developed faster at higher P levels. The maximal P-solubilizing capacity (of FePO4 and AlPO4) by root exudates was obtained earlier, and the capacity was greatest, at the highest P treatment. The increase of malonic, citric, malic, and piscidic acids in root exudates corresponded to the appearance of P-solubilizing capacity. These results suggest that the exudation of chelating organic acids from pigeonpea roots seems to be controlled not by P-deficiency, but by the plant growth stage.