Flowering Control of Elsholtzia angustifolia (Loes.) Kitag., a Short-Day Plant

This study was conducted to investigate the photoperiodic flowering response of Elsholtzia angustifolia. Plants were grown under 9/15 h (day/night) (short day, SD), 16/8 h (long day, LD), and nightinterruption (NI, 4 h around midnight) conditions. Supplemental lighting with a light intensity of 4μmol·m-2·s-1was applied for the LD and NI treatments. Plants under continuous SD conditionsdeveloped the first floral bud at 5 weeks after sowing during the seedling stage and showed 100%flowering at 9 weeks. Under continuous LD and NI conditions, there was no flowering, and plantscontinued vegetative growth only. Early flowering under continuous SD conditions showed a smallnumber of flowers. It was not desirable for marketable potted plant production, indicating that thereis a need for a certain period of vegetative growth before flowering. Among plants under LD and NIconditions, transfer to SD conditions was performed at 3 or 6 weeks after transplanting (WAT) tomanipulate the flowering time. The percent flowering was 100% when plants were transferred toSDs. On average, there were approximately 36 days to flowering from transfer to SD conditions at3 and 6 WAT, and there was no significant difference between the photoperiod and transfertreatments. The number of inflorescences significantly increased as the transfer date was delayed. The number of leaves and branches was also significantly increased by the delayed transfer date. These results indicate that E. angustifolia is an obligate SD plant and that non-forcing conditions,such as LD or NI, effectively inhibit early flowering. KCI Citation Count: 0