Phosphatidylglycerophosphate (PGP) phosphatase involved in the biosynthesis of phosphatidylglycerol (PG), a phosphoglycerolipid predominantly present in chloroplastic thylakoid membranes and which has important photosynthetic function; seems to use PGP 34:3, PGP 34:2 and PGP 34:1 as substrates (PubMed:27541283, PubMed:27614107, PubMed:29476828). Required for thylakoid membranes development and chloroplast function (PubMed:27541283, PubMed:27614107). Necessary for normal cell growth (PubMed:27614107). Required for root growth and columella cells organization (PubMed:29476828). 1,2-diacyl-sn-glycero-3-phospho-(1'-sn-glycero-3'-phosphate) + H2O = 1,2-diacyl-sn-glycero-3-phospho-(1'-sn-glycerol) + phosphate Optimum pH is 8. Phospholipid metabolism; phosphatidylglycerol biosynthesis; phosphatidylglycerol from CDP-diacylglycerol: step 2/2. Localized in chloroplast of leaf mesophyll cells, but in mitochondrion of root cells. Mainly expressed in inflorescences (especially in pollen) and, to a lower extent, in leaves, stems and siliques, as well as, at low levels, in roots (PubMed:27614107). Mostly expressed in hypocotyl, vasculatures, trichomes, guard cells and stigmas (PubMed:27541283). In the mature embryo, prominently expressed in the shoot apical meristem (SAM) (PubMed:27541283). In young seedlings, present in hypocotyls and mature part of roots, but not in root tips (PubMed:27541283). Later, also observed in the vasculature of cotyledons, in trichomes of emerging true leaves, and in joint part of the root to shoot (PubMed:27541283). In leaves, accumulates in guard cells and trichomes (PubMed:27541283). In flowers, mainly confined to the stigma of pistils and to the vasculature in the filament of stamens (PubMed:27541283). Pale green phenotype with reduced phosphatidylglycerol (PG) and chlorophyll contents but no defect in embryo development (PubMed:27541283, PubMed:27614107). Accumulation of phosphatidylglycerophosphate (PGP) 34:3, PGP 34:2 and PGP 34:1 lacking 16:1 (PubMed:27614107). Strongly reduced amounts of other thylakoid lipids such as monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG) and sulfoquinovosyldiacylglycerol (SQDG), especially under phosphate deprivation conditions (-P) (PubMed:27614107). Reduced amounts of chlorophyll, but unchanged photosynthetic quantum yield (PubMed:27614107). Altered chloroplasts development (e.g. reduced number of thylakoid membranes) and impaired photosynthetic activity (PubMed:27541283, PubMed:27614107). Reduced mesophyll cells size (PubMed:27614107). Strongly shorter roots associated with a defective order of columella cells in the root apices (PubMed:29476828). Plants lacking PTPMT1, PTPMT2 and PGPP1 have strongly shorter roots associated with a defective order of columella cells in the root apices, with stronger effect than in the single mutant pgpp1-1 (PubMed:29476828). Belongs to the HAD-like hydrolase superfamily.