MODELING TEMPERATURE AND PHOTOPERIOD INDUCTED FLOWERING IN LILIUM LONGIFLORUM

Emerged Lilium longiflorum Thunb. ‘Nellie White’ plants were placed for 6 weeks at one of 11 temperatures ranging from -2.5°C to 22.5°C (2.5° increments) and were exposed to a PPF of 10 μmol·s^-1·m^-2 from incandescent lamps for 9 hours per day (SD) or 24 hours per day (LD) during the temperature treatments (Experiment I). Unemerged plants were held at each temperature for either 2, 4, 6, or 8 weeks and emerged shoots were exposed to a PPF of 10 μmol·s^-1·m^-2 from incandescent lamps for 9 hours per day (Experiment II). After termination of the storage treatments, plants from both experiments were grown at 20°C in a greenhouse with a 9 hour photoperiod.
The effectiveness of a treatment in promoting flowering was determined by multiplying the relative effectiveness of a treatment in reducing total leaf number by the flowering percentage of the treatment.
The relative effectiveness of temperature in promoting flowering increased as the temperature decreased from 22.5°C to 5°C and as the treatment duration increased from 2 to 8 weeks.
All plants treated at 22.5°C remained vegetative irrespective of duration or photoperiod.
Short day plants had increasingly more leaves and flowers than long day plants as the treatment temperature increased from 0°C to 15°C. Long days were; at most, 47% as effective as a 5°C temperature treatment in promoting flowering.
The effect of temperature and long days on flower induction was additive.
All plants treated at -2.5°C froze.

Symposium on Bedding and Pot Plant Culture

Nathan E. Lange, Royal D. Heins

https://doi.org/10.17660/ActaHortic.1990.272.16