Culture methods for high hydrangenol and phyllodulcin contents in Hydrangea macrophylla subsp. serrata (Thunb.) Makino

Hydrangea macrophylla/Hydrangea macrophylla subsp. serrata cultivars are common ornamental plants, appreciated for their big and often colourful flowers. Some cultivars contain high amounts of dihydroisocoumarins (DHCs) which are of nutritional or medicinal interest. We cultured cuttings from two cultivars, which contain hydrangenol (HG) and phyllodulcin (PD), both DHCs, under greenhouse forcing conditions. Using peatmoss-based or inert substrates and drip or ebb-flow irrigation in addition with hydroponic fertilizers as well as full-spectrum, high-pressure sodium (HPS) lamps in short-day seasons, we aimed at improving biomass production and accumulation of HG and PD pre-harvest. The content of HG and PD was measured in young and old leaves after foliar application ofthree plant hormones, ethylene, salicylic acid and methyl jasmonate (MeJA). Repeated applications of MeJA significantly increased HG and PD contents, especially in young leaves of vegetative plants, in contrast to the other hormones. However, more than five applications of 60 mu mol MeJA per plant did not lead to further enhancements. The hormone applications had no significant positive impact on leaf fresh matter biomass. The biggest difference in biomass was observed between plants in vegetative and generative growth state. Our findings show, that HG and PD contents can be increased in plants repeatedly treated with MeJA, preferably during vegetative growth without influencing biomass production.