2019 Volume 18 Issue 4 Pages 373-379
This study was conducted to investigate the effects of the length of the light period and photosynthetic photon flux density (PPFD) in the growth chamber on the germination and growth of Eustoma grandiflorum after the wet treatment of seeds at 10°C. Seeds were sown in 200-cell trays, and then the wet treatment was applied for five weeks at 10°C under dark conditions. After this treatment, all seedlings were grown for five weeks in the growth chamber at a temperature of 27.5°C under light/dark conditions. When the average PPFD was 125 μmol・m–2・s–1, the germination rate eight days after transferring the cell tray into the growth chamber was 98% or higher regardless of the length of the light period of 12 to 24 h. After raising the seedlings for five weeks, the seedlings exposed to light periods of 20 and 24 h were significantly larger than at 12 h. For the seedlings grown with light periods of 20 h or 24 h, the number of days until bolting, flower budding, and flowering from transplantation was significantly fewer than at 12 h. When the light period was 24 h, the germination rate eight days after transferring into the growth chamber was about 95% or higher regardless of the PPFD from 50 to 125 μmol・m–2・s–1. The seedlings with PPFD at 100 and 125 μmol・m–2・s–1 were significantly larger than at 50 μmol・m–2・s–1. In seedlings grown with PPFD of 100 and 125 μmol・m–2・s–1, the number of days until bolting, flower budding, and flowering from transplantation was significantly fewer than at 50 μmol・m–2・s–1. Rosette plants were not found under all treatment conditions, and all seedlings bolted and subsequently bloomed. The cut flower characteristic forms were equivalent in both experiments regardless of the treatment. We concluded that the most suitable length of the light period for producing Eustoma grandiflorum seedlings in the growth chamber at a temperature of 27.5°C under light/dark conditions was over 20 h and the most suitable PPFD was 100 to 125 μmol・m–2・s–1.
