Accumulation of rare earth elements in corn after agricultural application

Using both pot and plot experiments, the dose-dependent accumulation of rar e earth elements (REs) in corn (Zea mays L.) after application of an agricu ltural REs mixture was measured. In the pot experiment, the dose-dependent accumulation of REs in corn root and stem was observed, but it could not be detected in corn leaf under the dosage of 20 mg REs kg(-1) soil (oven-dry mass). The non-observed effect concentration (NOEC) for accumulation of REs in corn seedling with the pot experiment was 1.0 mg REs kg(-1). In the plo t experiment, the dose-dependent accumulation was observed at an early stag e after application of REs and the NOEC value of 32 mg REs m(-2) was obtain ed. At harvest, no dose-dependent accumulation of REs was observed in any p art of the corn. These results fan be confirmed by the fingerprinting analy sis based on the differences between La to RE ratios in the REs mixture and in pot or plot soil. We observed that the plant shows no preference on ind ividual RE and the results of fingerprinting indicated clearly the incorpor ation of exogenous REs in plant tissues, in a similar manner as that observ ed in the dose-dependent distribution of RE concentrations. The results ind icated also a translocation process of REs From plant root to leaf when app lied to soil or from leaf to root when applied to leaf. A homeostatic regul ation mechanism for excessive uptake of REs in plants is suggested to regul ate the concentrations of REs in the plant.