Temperature and Photoperiod Effect on Flower Numbers in Lilium longiflorum Thunb.1

Abstract ‘Nellie White’ and ‘Ace’ lily plants from non-vernalized bulbs were placed in growth chambers for temperature and photoperiod treatments at various stages of development. Under a 16-hour photoperiod, a 21.1°/12.8°C day/night temperature regime was optimal from shoot emergence to flower bud initiation for early flowering and high flower numbers. The increases in the flower numbers were due to the increased number of secondary and tertiary flower buds. Primary buds were constant regardless of temperature and photoperiod treatment. Under a 16-hour photoperiod a night temperature of 7.2° favored secondary bud formation, while a 15.6° night temperature favored tertiary bud formation. Under a 12-hour photoperiod from floral initiation to visible buds, a 18.3°/15.6°C day/night temperature regime was optimal for early flowering and a minimum loss of flower buds. Under a 12-hour photoperiod from the visible bud stage to anthesis, a 21.1°/18.3°C day/night temperature regime was optimal for early flowering with the fewest aborted tertiary buds.