This magnesium-dependent enzyme catalyzes the hydrolysis of ATP coupled with the translocation of calcium from the cytosol to an endomembrane compartment (Probable). Involved in calcium-enhanced root growth, in tolerance to toxic levels of manganese and in secretory processes (PubMed:18567829). Has a crucial role in manganese nutrition, but is not involved in transporting copper, iron or zinc (PubMed:18024560). ATP + Ca(2+)(in) + H2O = ADP + Ca(2+)(out) + H(+) + phosphate Expressed in root cap, in elongation and differentiation zones of roots, in vascular tissues of roots, leaves, floral pedicels and style, in leaves, including hydathodes and guard cells, in stamens, in petals, in sepals and in siliques. Not induced by manganese or zinc. ECA3 is functionally distinct from ECA1 and is localized to a separate compartment. Belongs to the cation transport ATPase (P-type) (TC 3.A.3) family. Type IIA subfamily.