Exhibits phosphatidate phosphatase (PAP) activity in vitro. May play a primary role as PAP in plastids. Inhibited by Mg(2+). Optimum pH is 6.0-8.0. Expressed in root tips, root branch points, vascular tissue of cotyledons and leaves, pistil, anthers and filaments. Lethal effect when homozygous, due to defect in pollen germination and pollen tube growth. Belongs to the PA-phosphatase related phosphoesterase family.