The Influence of Light on Lily (Lilium longiflorum Thunb.). II. Influence of Photoperiod and Light Stress on Flower Number, Height, and Growth Rate1

Abstract

Abstract Placing lily plants in complete darkness, with or without 12 hr per day of low intensity incandescent (Inc) lighting for 5 days at 5 day intervals during the first 40 days of growth after emergence (E) had no influence on final flower bud number. Low intensity Inc lighting given as a 4 hr night interruption under natural daylight (ND) conditions for 10 days at various intervals during the first 40 days after E had no horticulturally significant influence on flower bud number. Final lily plant heights were controlled by photoperiod. Heights were reduced when plants were forced under 8 hr photoperiods (SD) when compared to ND forced plants. Heights of ‘Ace’ and ‘Nellie White’ plants were reduced by 29% and 45% when forced under SD from E to flower (F), by 19% and 42% when forced from 30 days after E to F, and by 20% and 20% when forced from visible bud to F. Repetitive light/dark cycles of 4, 6 or 12 hr had no effect on lily flower bud development rate from the time buds were 6–12 cm in length to anthesis.