Reductase involved in lignan biosynthesis. Catalyzes the enantioselective conversion of (-)-pinoresinol into (-)-lariciresinol and of (-)-lariciresinol into (+)-secoisolariciresinol. Abstracts the 4R-hydride from the NADPH cofactor during catalysis. (-)-lariciresinol + NADP(+) = (-)-pinoresinol + H(+) + NADPH (+)-secoisolariciresinol + NADP(+) = (-)-lariciresinol + H(+) + NADPH Dimer. Expressed in seeds and roots, but not in stems. Detected in leaves. Belongs to the NmrA-type oxidoreductase family. Isoflavone reductase subfamily.