Reductase involved in lignan biosynthesis. Catalyzes the enantioselective sequential conversion of (+)-pinoresinol into (+)-lariciresinol and of (+)-lariciresinol into (-)-secoisolariciresinol. Can also convert with a lower efficiency (-)-pinoresinol into (-)-lariciresinol, but not (-)-lariciresinol into (+)-secoisolariciresinol. Abstracts the 4R-hydride from the NADPH cofactor during catalysis. (+)-lariciresinol + NADP(+) = (+)-pinoresinol + H(+) + NADPH (-)-secoisolariciresinol + NADP(+) = (+)-lariciresinol + H(+) + NADPH (-)-lariciresinol + NADP(+) = (-)-pinoresinol + H(+) + NADPH Dimer. Leu-164, Gly-267 and Phe-271 are involved in enantiospecific binding of (+)-pinoresinol while in PLR_Tp1, a 'Val-267' and a symmetric substitution between Phe and Leu favor binding of the (-)-antipode of pinoresinol. Belongs to the NmrA-type oxidoreductase family. Isoflavone reductase subfamily.