Natural Chilling and Limited Inductive Photoperiod Affect Flowering in Two Asteraceae Genera

Abstract

<jats:p>To examine the effects of chilling and a limited inductive photoperiod (LIP) on flowering of <jats:italic>Chrysanthemum superbum</jats:italic> Bergmans ex J. Ingram `G. Marconi' and `Snow Lady', <jats:italic>Coreopsis grandiflora</jats:italic> Hogg `Sunray', and <jats:italic>Coreopsis lanceolata</jats:italic> L. `Early Sunrise', seeds were sown and plants were maintained in the greenhouse in short days (SDs) for 7 weeks, followed by 4 months of natural outdoor chilling for all plants except 10 of each cultivar, which remained in the greenhouse under SDs for the duration of the experiment. Upon return to greenhouse conditions, 10 plants of each cultivar were placed in SDs, all other chilled plants were placed in long-days (LDs) and subsequently transferred to SDs after receiving 6, 8, 10, 12, 14, 16, 18, 20, or 22 LD cycles. Ten chilled plants of each cultivar remained in LDs for the duration of the experiment. Continuous SDs without chilling resulted in 70%, 40%, 20%, and 10% flowering in `Snow Lady', `Early Sunrise', `Sunray,' and `G. Marconi', respectively. Chilling, followed by a return to continuous SDs, improved flowering in all cultivars compared to SDs without chilling. The number of LD cycles required for 100% flowering varied with cultivar. Ninety percent of the chilled `Early Sunrise' plants flowered with no LD cycles, and 100% flowering was produced by as few as six LD cycles. In `Snow Lady', 100% flowering occurred in chilled plants with no LD cycles and those receiving at least 10 LD cycles. With only six or eight LD cycles, 90% and 80% of these plants, respectively, still flowered. The percentage of `G. Marconi' and `Sunray' plants flowering ranged from 40% to 100% in the chilled treatments, with a general trend for more flowering with an increase in the number of LD inductive cycles. Continuous LDs following chilling resulted in as high or higher percent flowering than any other treatments (100% for `G. Marconi' and 90% for `Sunray'). The effects of LIP were evident in both <jats:italic>Coreopsis</jats:italic> cultivars but in neither <jats:italic>Chrysanthemum superbum</jats:italic> cultivar. There was a linear relationship between the number of LDs received and stem length at first flower in `Sunray' and `Early Sunrise'. In both cultivars, a reduction in stem elongation of about 10 cm occurred when plants received only 6 LDs compared to 22 LDs. The number of days from the start of LDs to first flower increased linearly as the number of LD cycles before the transfer back to SDs increased.</jats:p>

Flowering and Morphogenesis of Kalanchoe in Response to Quality and Intensity of Night Interruption Light

“…The NI using low-intensity light emitting diodes (LEDs) is supposed to slightly affect the net photosynthesis and ensure growth promotion in tomatoes [6]. NI has effectively accelerated the growth and development of herbaceous LDPs such as Campanula carpatica [7], Coreopsis grandiflorum [8], and Cyclamen persicum [9] in SD seasons. By inducing vegetative growth, NI has also been used to prevent or delay the flowering of herbaceous short-day plants (SDPs) such as Dahlia pinnata [10] and Dendranthema grandiflorum [11].…”

Comparing Flowering Responses of Long-day Plants under Incandescent and Two Commercial Light-emitting Diode Lamps

“…Electrical lighting is commonly operated at the end of the day (day-extension lighting) or in the middle of the night (NI lighting) to create an artificial LD. A 4-h NI promotes rapid flowering of a range of LDP including campanula (Campanula carpatica), coreopsis (Coreopsis grandiflora), and lavender (Lavandula angustifolia) (Damann and Lyons, 1996;Runkle et al, 1998). A photosynthetic photon flux (PPF) of %1 mmolÁm -2 Ás -1 is needed to elicit a photoperiodic response from conventional light sources such as INC or high-pressure sodium (HPS) lamps (Whitman et al, 1998).…”

Prevernalization Daily Light Integral and Vernalization Temperature Influences Flowering of Herbaceous Perennials

“…Flowering percentage of C. grundifolia 'Sunray' was not influenced by DLI but generally increased with vernalization duration, and there was no general pattern on optimal vernalization temperature in this experiment. Damann and Lyons (1996) reported that 4 months natural chilling followed by continuous short-day or long-day conditions resulted in 40% or 90% flowering in 'Sunray', respec-tively, and only 20% flowered for unchilled plants. No plants flowered without vernalization in any short-day or long-day conditions (Damann and Lyons, 1993), which is in agreement with our present study.…”