Acylhydrolase that catalyzes the hydrolysis of 1,3-diacylglycerol (1,3-DAG) and 1-monoacylglycerol (1-MAG) at the sn-1 position. High activity toward 1,3-DAG and 1-MAG, but low activity toward 1,2-diacylglycerol (1,2-DAG) and 1-lysophosphatidylcholine (1-LPC), and no activity toward phosphatidylcholine (PC), monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), triacylglycerol (TAG) and 2-monoacylglycerol (2-MAG). May be involved in the negative regulation of seedling establishment by inhibiting the breakdown, beta-oxidation and mobilization of seed storage oils. Optimum pH is 5-6 with 1,3-DAG as substrate and at 30 degrees Celsius. Expressed in seedlings, stems and siliques, and, to a lower extent, in flowers. Mildly fast-growing seedlings regardless of the presence of an exogenous carbon source, accompanied by a better beta-oxidation and mobilization of seed storage oils. Belongs to the AB hydrolase superfamily. Lipase family. Truncated N-terminus.