Involved in the latter stages of lignin biosynthesis (PubMed:24985707). Catalyzes one of the last steps of monolignol biosynthesis, the conversion of cinnamoyl-CoAs into their corresponding cinnamaldehydes (PubMed:25217505, PubMed:24985707). Mediates the conversion of feruloyl CoA to coniferylaldehyde (PubMed:25217505, PubMed:24985707). Also active toward p-coumaroyl-CoA and sinapoyl-CoA (PubMed:25217505, PubMed:24985707). Involved in the production of floral volatile phenylpropanoids in flowers of fragrant cultivars (e.g. cv. Mitchell and cv. V26) from cinnamic acid, a common precursor with the anthocyanin biosynthesis pathway involved in flower pigmentation (PubMed:24985707). (E)-coniferaldehyde + CoA + NADP(+) = (E)-feruloyl-CoA + H(+) + NADPH (E)-4-coumaraldehyde + CoA + NADP(+) = (E)-4-coumaroyl-CoA + H(+) + NADPH (E)-sinapaldehyde + CoA + NADP(+) = (E)-sinapoyl-CoA + H(+) + NADPH (E)-cinnamaldehyde + CoA + NADP(+) = (E)-cinnamoyl-CoA + H(+) + NADPH Inhibited by sodium iodide-mediated oxidation. kcat is 1.2 sec(-1) with p-coumaroyl-CoA as substrate (PubMed:25217505). kcat is 5.8 sec(-1) with feruloyl-CoA as substrate (PubMed:25217505). kcat is 3.4 sec(-1) with sinapoyl-CoA as substrate (PubMed:25217505). Optimum pH is 6. Aromatic compound metabolism; phenylpropanoid biosynthesis. Expressed in flowers, leaves and stems. Highly expressed in the scent-producing corollas and tubes of two days old flowers, reaching a maximum at day three post-anthesis, and, to a lower extent, in other floral tissues (e.g. ovary, pistil, sepals and stamen). Circadian-regulation with peak levels occurring in flowers during the light period, in the afternoon. The formation of a reversible disulfide bond reduces activity by perturbing the positioning of nearby catalytic residues. No visible effect on the emission and internal pools of phenylpropene and benzenoid compounds, but increased accumulation of feruloyl-CoA, p-coumaroyl-CoA and vanillin (PubMed:24985707). Reduced lignin content (PubMed:24985707). Belongs to the NAD(P)-dependent epimerase/dehydratase family. Dihydroflavonol-4-reductase subfamily.