Control of Floral Scent Emission by Inhibitors of Phenylalanine Ammonia-lyase in Cut Flower of Lilium cv. ‘Casa Blanca’

Abstract

Oriental hybrid lily flowers have a pleasant fragrance. Especially in a confined space, however, the scent can be perceived as too strong and therefore unpleasant. Our analysis of the major scent compounds in cut flowers of ‘Casa Blanca’ lilies, which is one of the most popular oriental hybrid lilies in Japan, identified two aromatics (benzyl alcohol and iso-eugenol) and two terpenoids (linalool and cis-ocimene). In addition, p-creosol (aromatics) was detected as a minor component. Based on sensual impressions, we assumed that iso-eugenol and p-creosol were the main causes of the unpleasant odor. We concluded that inhibitors of the biosynthesis of aromatics could decrease concentrations of these compounds and make the fragrance of ‘Casa Blanca’ less unpleasant. The biosynthesis of aromatics is generally catalyzed by phenylalanine ammonia-lyase (PAL). We used aminooxy acetic acid (AOA) and L-2-aminooxy-3-phenylpropionoic acid (AOPP) as PAL inhibitors. Application of AOA and AOPP at 0.1 mM and 1.0 mM by vase treatment decreased the emissions of scent compounds. For practical application, AOA was selected because of its much lower cost. Continuous treatment with AOA decreased the emissions of scent compounds to 10 to 20% of the control at a constant ratio at all times of day on the second and third days after flowering when ‘Casa Blanca’ emitted the greatest amounts of scent compounds. Similar effects were found on the last day of flowering. Under certain conditions, temporary treatment for 24 h evoked similar effects as continuous treatment. Application of 1.0 mM AOA caused chemical injury to the tepals, but 0.1 mM AOA did not. Treatment of plants with opened flowers was less effective than treatment at a late bud stage. In summary, continuous post-harvest treatment with 0.1 mM AOA of ‘Casa Blanca’ at late flower bud stages can decrease the emissions of scent compounds and render the fragrance milder without affecting flower morphology through its period of use as an ornamental.