Phosphatidic acids (PAs) are a key intermediate in phospholipid biosynthesis, and a central element in numerous signalling pathways. Functions of PAs are related to their fundamental role in molecular interactions within cell membranes modifying membrane bending, budding, fission and fusion. Here we tested the hypothesis that PAs are capable of direct transport of ions across bio-membranes. We have demonstrated that PAs added to the maize plasma membrane vesicles induced ionophore-like transmembrane transport of Ca ²⁺ , H ⁺ and Mg ²⁺ . PA-induced Ca ²⁺ fluxes increased with an increasing PAs acyl chain unsaturation. For all the PAs analysed, the effect on Ca ²⁺ permeability increased with increasing pH (pH 8.0 > pH 7.2 > pH 6.0). The PA-induced Ca ²⁺ , Mg ²⁺ and H ⁺ permeability was also more pronounced in the endomembrane vesicles as compared with the plasma membrane vesicles. Addition of PA to protoplasts from Arabidopsis thaliana (L.) Heynh. roots constitutively expressing aequorin triggered elevation of the cytosolic Ca ²⁺ activity, indicating that the observed PA-dependent Ca ²⁺ transport occurs in intact plants.