Involved in lignin biosynthesis (PubMed:16443696, PubMed:21912859). Catalyzes the final step specific for the production of lignin monomers. Catalyzes the NADPH-dependent reduction of coniferaldehyde and sinapaldehyde to their respective alcohols (PubMed:16443696). Plays the major role in monolignol biosynthesis. Functions cooperatively with COMT in the culm internodes for the biosynthesis of monolignols, the lignin precursors. May be involved in lignin biosynthesis in leaves and roots (PubMed:21912859). (E)-cinnamyl alcohol + NADP(+) = (E)-cinnamaldehyde + H(+) + NADPH Binds 2 Zn(2+) ions per subunit. Aromatic compound metabolism; phenylpropanoid biosynthesis. Homodimer. Expressed in roots behind the root tips in the pericycle region and layer of cortical cells adjacent to the exodermis. Expressed in vascular bundles and lateral veins of leaf sheaths and blades. Expressed in the vicinity of vascular bundles in the first internode below the inflorescence (PubMed:15452707, PubMed:16443696). Highly expressed in the culm (PubMed:21912859). Reduced lignin content, reddish-brown coloration of panicles and internodes, and golden yellow seeds. Belongs to the zinc-containing alcohol dehydrogenase family.