XVI International Botanical Congess

P deficiency-induced adaptations of white lupin, involved in P acquisition and mobilization of sparingly available P sources, are predominantly confined to proteoid roots, and moreover to distinct stages during proteoid root development. Increased accumulation and exudation of citric acid and a concomitant release of protons were found to be predominantly restricted to mature root clusters in later stages of P deficiency. Inhibition of citrate exudation by exogenous application of anion channel blockers may indicate involvement of an anion channel. P deficiency-induced accumulation and subsequent exudation of citric acid seems to be a consequence of both increased biosynthesis and reduced metabolization of citric acid in the proteoid root tissue.