May be involved in the biosynthesis of hydroxylated tetraketide compounds that serve as sporopollenin precursors (the main constituents of exine). Acts on tetraketide alpha-pyrones and reduces the carbonyl function on the tetraketide alkyl chain to a secondary alcohol function. A number of isoforms are produced. According to EST sequences. No visible phenotype under normal growth conditions. Belongs to the NAD(P)-dependent epimerase/dehydratase family. Dihydroflavonol-4-reductase subfamily.