Reductase involved in lignan biosynthesis. Catalyzes the sequential conversion of pinoresinol into lariciresinol and of lariciresinol into secoisolariciresinol. Abstracts the 4R-hydride from the NADPH cofactor during catalysis (By similarity). Dimer. Expressed in seed coats, but not in embryos, leaves, stems and roots. Expressed during seed development, with a pic at mid-maturation. Up-regulated by abscisic acid and down-regulated by gibberellins. Belongs to the NmrA-type oxidoreductase family. Isoflavone reductase subfamily.