Important as a means of generating NADPH for biosynthetic reactions. May be a main source of cytosolic NADPH for mannitol biosynthesis in leaves. D-glyceraldehyde 3-phosphate + H2O + NADP(+) = (2R)-3-phosphoglycerate + 2 H(+) + NADPH Competitive inhibition by NADPH, 3-phospho-D-glycerate and ATP. Measured at pH 7.7 and 30 degrees Celsius for all experiments. Expression increases during leaf development. Not expressed in senescent leaves. By salt stress. Belongs to the aldehyde dehydrogenase family.