Phosphate induced carboxylate and proton release by tomato roots

Exudation of carboxylic anions and protons by plant roots Flays an important role in mobilizing soil P under P-deficiency conditions. The objective of this work was to quantify short-term (6 h) 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 mu mol 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).