Cadmium uptake and subcellular distribution in rice plants as affected by phosphorus: Soil and hydroponic experiments

Abstract

High cadmium (Cd) concentrations are a serious environmental problem in various agro-ecosystems and urban areas. Since mobile Cd in the soil can be accumulated in the food chain by plant uptake, remediation techniques to fx Cd in the soil in situ are urgently required, for which the application of phosphorus (P) is auspicious. The effects of P on soil pH, Cd phytoavailability, and Cd distribution with regard to rice plants were examined in a pot experiment using soil contaminated with 82 mg Cd kg-1. A commercial P fertilizer (0-52-34, containing 52% P2O5 and 34% K2O) was applied to the soil to reach P concentrations of 0 (the control), 50, 200, and 1000 mg P kg-1 above the baseline P concentration of the soil. P-application increased the soil pH and caused a redistribution of Cd to less mobile fractions. Plant growth was also enhanced by P addition. Plant Cd uptake was only signifcantly reduced in mature plants receiving a P-application rate of 1000 mg P kg-1. Additionally, a hydroponic experiment was carried out to study the effects of different P concentrations on the subcellular distribution of Cd in rice plants. When a P-application of 1000 mg L-1 was applied, the Cd proportions in the cell walls increased by 7% in the roots and 10% in the shoots, while reductions for the other fractions were observed, hinting at the occurrence of a detoxifying effect of P on the rice plant's Cd concentration.