Required to supply glycerol-3-phosphate in the chloroplast for the synthesis of glycerolipids. Required for activation of systemic acquired resistance (SAR). Provision of glycerol-3-phosphate may be involved in generating lipid signals necessary for mediating defense responses and SAR. NAD(+) + sn-glycerol 3-phosphate = dihydroxyacetone phosphate + H(+) + NADH Membrane lipid metabolism; glycerophospholipid metabolism. No visible phenotype under normal growth conditions, but leaves have decreased levels of hexadecatrienoic fatty acid (16:3) and increased levels of oleic acid (18:1). Belongs to the NAD-dependent glycerol-3-phosphate dehydrogenase family.