Hydrolyzes glycerol-phospholipids at the terminal phosphodiesteric bond to generate phosphatidic acids (PA) (PubMed:18364466). Active with phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and phosphatidylserine (PS) as substrates (PubMed:18364466). No activity toward phosphatidylinositol (PI) or PIP2 (PubMed:18364466). Positively mediates plant responses to hyperosmotic stresses and promotes root growth, flowering, and stress avoidance (PubMed:18364466, PubMed:19704505). Not involved in the abscisic acid regulation of stomatal movement and transpirational water loss (PubMed:18364466). a 1,2-diacyl-sn-glycero-3-phosphocholine + H2O = a 1,2-diacyl-sn-glycero-3-phosphate + choline + H(+) Expressed in buds, flowers, siliques, stems, old leaves and roots (PubMed:18364466). Expressed in the sieve elements (PubMed:25081480). Regulated by the transcription factors NAC045 and NAC086. C2 domain is a calcium-binding fold, and the binding promotes the protein association with membranes. A lower affinity toward calcium can be anticipated for PLD alpha due to the absence of two potential calcium ligands. No visible phenotypes when grown under normal conditions, but increased sensitivity to salinity and water deficiency (PubMed:18364466). Late flowering in slightly dry conditions (PubMed:18364466). Decreased sensitivity to glucose (PubMed:19704505). Belongs to the phospholipase D family. C2-PLD subfamily.