Geochemical behaviour of rare earths in Vitis vinifera grafted onto different rootstocks and growing on several soils

The geochemical behaviour of lanthanides and yttrium(Rare Earth Elements, REEs) has been investigatedmainly in geological systems where these elements represent the best proxies of processes involving the occurrence of an interface between different media. This behaviour is assessed according to features recorded in sequences of REE concentrations along the REE series normalised with respect to a reference material. In this study, the geochemical behaviour of REE was investigated in different parts of Vitis vinifera specimens grown off-soil, on soils of different nature and grafted onto several rootstocks in order to evaluate effects induced by these changes. The results indicated that roots are the plant organs where REEs are preferentially concentrated, in particular elements from Sm to Ho (middle REE, MREE) whereas Eu enrichments occur in aerial parts. The geochemical behaviour of REE suggests that MREE enrichments in roots are due to preferential MREE interactions with biological membranes or to surface complexation with newly formed phosphates. Eu-positive anomalies suggest that Eu3+ can form stable organic complexes in place of Ca2+ in several biological processes in xylem fluids. The possibility that Eu mobility in these fluids can be enhanced by its reductive speciation as Eu2+ cannot be ruled out. The assessment of the geochemical behaviour of REE according to the theory of the Tetrad Effect carried out confirms that REEs coming fromsoil are scavenged onto root tissues or mineral surfaceswhereas their behaviour in aerial parts of V. vinifera is driven by dissolved complexation.