Phosphate induced carboxylate and proton release by tomato roots

Exudation of carboxylic anions and protons by plant roots plays an important role in mobilizing soil P under P-deficiency conditions. The objective of this work was to quantify short-term (6h) carboxylate and H⁺ exudation by tomato roots in response to P concentration (0, 0.1,0.5 and 1.0 mM P) in nutrient solution (C(p)). The exudation rate of tri- and dicarboxylates decreased exponentially with increasing C(p), from 0.3 to 0.03 μmol plant^-1 6h^-1. At low C(p), the predominant exudates were fumarate, citrate and succinate, while at C(p)=0.5 and 1.0 mM the prevalent anions were succinate and citrate. The solution pH declined sharply as C(p) was lowered from 0.1 (pH=4.2) to 0 mM P (pH=3.7).