Reductase involved in lignan biosynthesis (PubMed:18347017). Unlike conventional pinoresinol reductases that can reduce both pinoresinol and lariciresinol, PRR2 shows a strict substrate selectivity for (-)-pinoresinol (PubMed:18347017). No activity with (+)-pinoresinol or lariciresinol (PubMed:18347017). Abstracts the 4R-hydride from the NADPH cofactor during catalysis (PubMed:18347017). (-)-lariciresinol + NADP(+) = (-)-pinoresinol + H(+) + NADPH Forms homodimers. Expressed in roots. Detected in stems. No significant difference in lariciresinol content (PubMed:18347017). Prr1 and prr2 double mutants show a complete inhibition of lariciresinol biosynthesis (PubMed:18347017). Belongs to the NmrA-type oxidoreductase family. Isoflavone reductase subfamily.