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 differentiation and elongation zones of primary and lateral roots. Expressed in the hypocotyl, cotyledon and leaf veins, hydathodes and trichomes. In stems, expressed in the vascular cambium region. Expressed in the style, anthers, stamen filaments, vascular tissues of sepals and stigmatic regions in flowers, and abscission, style and stigmatic regions of siliques and seed testa. Belongs to the zinc-containing alcohol dehydrogenase family.