Rare earth elements （REEs） were reported to have adverse biology effects on plant growth and production. However, whether REEs are involved in plant hormone abscisic acid signal is not clear. Here we reported that REE lanthanum （La） interacted with abscisic acid （ABA） in the regulation of seed germination and root growth in model plant Arabidopsis. La3＋at a concentration of 10 μmol/L alleviated ABA depression of seed germination and reversed ABA inhibition of root elongation growth in Arabidopsis. Previous studies showed that ABA could promote root hair development. In the present study, La3＋inhibited root hair development promoted by ABA. Moreover, La3＋inhibited H2O2 generation induced by ABA in root cells. Therefore we inferred that La3＋might interact with ABA upstream of H2O2 generation.
