Involved in lignin biosynthesis. Catalyzes the final step specific for the production of lignin monomers. Catalyzes the NADPH-dependent reduction of coniferaldehyde, 5-hydroxyconiferaldehyde, sinapaldehyde, 4-coumaraldehyde and caffeyl aldehyde to their respective alcohols. (E)-cinnamyl alcohol + NADP(+) = (E)-cinnamaldehyde + H(+) + NADPH Binds 2 Zn(2+) ions per subunit. Aromatic compound metabolism; phenylpropanoid biosynthesis. Homodimer. Expressed in the primary and lateral roots, and root caps. Expressed in the hypocotyl, cotyledon veins and hydathodes. In stems, expressed in the vascular cambium, interfascicular cambium and developing xylem. Expressed in the style, anthers, stamen filaments, vascular tissues of sepals, stigmatic regions in flowers, and abscission and style regions of siliques. Belongs to the zinc-containing alcohol dehydrogenase family.