Adsorption of Phosphate by Iron Plaque on Rice Roots in Relation to Phosphate Uptake by Rice

Two rice genotypes differed in tolerance to iron toxicity were used to investigate the adsorption of phosphate by iron plaque on rice roots and subsequent effect on P absorption by rice. Great variation in quantities of iron plaque was observed between two genotypes, resulting in the difference in phosphate adsorption. The amount of P adsorbed increased with the increasing quantity of iron plaque on rice roots, which was indicated by a significant positive correlation between the quantity of iron plaque and its phosphate adsorbed. Phosphate adsorbed by iron plaque was likely to be a chemical process which was accomplished within 0.5-1.0 hour. The accumulation of phosphate by iron plaque remarkably enhanced the phosphorus uptake by rice, which suggested that the adsorbed phosphate was an important pool of phosphorus available to rice under the flooding conditions.