Lanthanum tolerance and accumulation characteristics of two Eucalyptus species

Because of extensive mining of rare earth elements (REEs) and overuse of REE-containing fertilizers, the remediation of soils polluted with REEs such as lanthanum (La) has become an international concern. In this study, pot and plot experiments were conducted to investigate the La tolerance and accumulation of a Eucalyptus grandis × Eucalyptus urophylla hybrid, Guanglin 9 (Gn9) and E. grandis 5 (Eg5). In the pot experiment, the two species grew normally in soil added La concentrations below 500 mg kg−1, and shoot biomass showed no significant decrease compared with the control. Peroxidase and catalase activities and glutathione and soluble protein concentrations generally displayed exponential, quadratic or other non-linear increases in response to increasing soil La concentrations. Maximum La accumulations in shoots of Gn9 and Eg5 in the pot experiment were 0.46 and 0.57% of soil La, respectively, with corresponding accumulations in the plot experiment of 87 and 80 mg plant−1. Most bioconcentration and translocation factors in shoots were less than the critical value (1.0). These findings indicate that the two species may be potentially useful for the remediation of La-polluted soil.