PA2 catalyzes the calcium-dependent hydrolysis of the 2-acyl groups in 3-sn-phosphoglycerides. Releases lysophospholipids (LPLs) and free fatty acids (FFAs) from membrane phospholipids in response to hormones and other external stimuli. Regulates the process of cell elongation and plays important roles in shoot gravitropism by mediating auxin-induced cell elongation. Involved in stomatal opening in response to light. Plays a role in pollen development and germination and tube growth. a 1,2-diacyl-sn-glycero-3-phosphocholine + H2O = a 1-acyl-sn-glycero-3-phosphocholine + a fatty acid + H(+) Binds 1 Ca(2+) ion per subunit. Inhibited by aristolochic acid. A number of isoforms are produced. According to EST sequences. Ubiquitous but expressed at a low level. Detected in vascular tissues and in the guard cells. Predominantly detected in pollen. Expressed in the actively growing young stages of Arabidopsis seedlings. When plants grew, however, expression was evident only in cotyledons, primary leaves, and hypocotyls. The activity decreased in the secondary leaves, being detectable only in vascular tissues. In the roots as well, expression was localized mostly in vascular tissues. Expression becomes highly active when floral shoots bolted, especially in the young or actively growing tissues of inflorescence stems. Continuously expressed during pollen development. By auxin. By light. RNAi mutant exhibits delayed light-induced stomatal opening. The enzyme has a preference towards palmitoyl acyl chain over linoleoyl acyl chain. It also has a slight preference for phosphatidylethanolamine over phosphatidylcholine. Belongs to the phospholipase A2 family.