Hydrolyzes glycerol-phospholipids at the terminal phosphodiesteric bond to generate phosphatidic acids (PA). Plays an important role in various cellular processes, including phytohormone action and response to stress, characterized by acidification of the cell (PubMed:9437863). Involved in wound induction of jasmonic acid (PubMed:11090221). May be involved in membrane lipid remodeling (PubMed:11239826). Probably involved in freezing tolerance by modulating the cold-responsive genes and accumulation of osmolytes (PubMed:16949955). Can use phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) as substrates, both in presence or in absence of PIP2 (PubMed:9578608). Its main substrate is phosphatidylcholine (PubMed:11239826). Stimulates the intrinsic GTPase activity of GPA1 upon binding (PubMed:14594812). Mediates the abscisic acid effects on stomata through interaction with GPA1 and the production of phosphatidic acid that bind to ABI1 (PubMed:17261695, PubMed:17565616). Involved in seed aging and deterioration (PubMed:17565616). Involved in microtubule stabilization and salt tolerance (PubMed:23150630). Involved in abscisic acid-induced stomatal closure (PubMed:22392280). a 1,2-diacyl-sn-glycero-3-phosphocholine + H2O = a 1,2-diacyl-sn-glycero-3-phosphate + choline + H(+) Ca(2+) requirement for activity depends on pH. Active either under acidic conditions with micromolar levels of calcium (PIP2-dependent) or at neutral pH with millimolar levels of calcium (PIP2-independent). Not inhibited by neomycin. Optimum pH is 4.5 to 5.0 in the presence of micromolar levels of Ca(2+) and PIP2. Optimum pH is 5.5 to 6.5 in the presence of millimolar levels of Ca(2+). Interacts with GPA1 (PubMed:14594812, PubMed:16614222, PubMed:23913032). This binding inhibits PLDALPHA1 activity and is relieved by GTP (PubMed:14594812). Not found in chloroplast or nuclei. The distribution of this conventional PLD between membrane-associated and soluble fractions varied from organ to organ and is calcium-regulated. Activation or wounding increases association of preexisting enzyme with membranes. Highly expressed in roots, stems and flowers, moderately in leaves, seedlings and siliques. Not detected in seeds. Up-regulated by abscisic acid and ethylene (PubMed:9437863). Up-regulated by salt, dehydration and osmotic stresses (PubMed:19017627). Not regulated by abscisic acid (PubMed:22392280). C2 domain is a calcium-binding fold, and the binding induces conformational changes, promoting the protein association with membranes. These conformational changes occure at millimolar Ca(2+) concentrations. Binds also PIP2. A lower affinity toward calcium can be anticipated for PLD alpha due to the absence of two potential calcium ligands. No visible phenotype under normal growth conditions, but improved resistance of the seeds to deterioration during storage (PubMed:17565616). Insensitivity to abscisic acid for both promotion of stomatal closure and inhibition of stomatal opening (PubMed:16614222). Hypersensitivity to hyperosmotic stress (PubMed:19017627). Increased NaCl-induced disorganization of microtubules (PubMed:23150630). No effect on abscisic acid-induced stomatal closure (PubMed:22392280). Pldalpha1 and plddelta double mutants have a suppressed abscisic acid-induced stomatal closure (PubMed:22392280). Belongs to the phospholipase D family. C2-PLD subfamily. Truncated N-terminus.