Low phosphate (Pi) availability is one of the major constraints for plant productivity in natural and agricultural ecosystems. Plants have evolved a myriad of developmental and biochemical mechanisms to increase internal Pi uptake and utilization efficiency. One important biochemical pathway leading to an increase in internal Pi availability is the hydrolysis of phospholipids. Hydrolyzed phospholipids are replaced by nonphosphorus lipids such as galactolipids and sulfolipids, which help to maintain the functionality and structure of membrane systems. Here we report that a member of the Arabidopsis phospholipase D gene family ( PLDZ2 ) is gradually induced upon Pi starvation in both shoots and roots. From lipid content analysis we show that an Arabidopsis pldz2 mutant is defective in the hydrolysis of phospholipids and has a reduced capacity to accumulate galactolipids under limiting Pi conditions. Morphological analysis of the pldz2 root system shows a premature change in root architecture in response to Pi starvation. These results show that PLDZ2 is involved in the eukaryotic galactolipid biosynthesis pathway, specifically in hydrolyzing phosphatidylcholine and phosphatidylethanolamine to produce diacylglycerol for digalactosyldiacylglycerol synthesis and free Pi to sustain other Pi-requiring processes.