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ISHS Acta Horticulturae 515: XXV International Horticultural Congress, Part 5: Culture Techniques with Special Emphasis on Environmental Implications Chemical, Physical and Biological Means of Regulating Crop Growth in Ornamentals and Other Crops

EFFECTS OF LIGHTING REGIMES ON FLOWERING OF DELPHINIUM HYBRIDS 'PACIFIC GIANTS'

Authors:   C. Dalla Guda, C. Cervelli, E. Farina
Keywords:   Delphinium, cut flower, flowering, ligth response
Abstract:
Plants of seven Delphinium cultivars 'Giant Pacific Court hybrids' obtained by a summer sowing and transplanted in cold greenhouse on October were grown at Sanremo (Riviera dei Fiori, Italy) in different lighting regimes applied from planting up to the end of April. Lighting treatments were: a) Normal Day (ND); b) Long Day (LD) provided by incandescent lamps (day lenghtening up to 16 hrs; P.P.F.D. of 1.1 ± 0.1 μmol m-2 sec-1); c) Long Day / High Intensity (LD/HI) provided by incandescent and High Pressure Sodium lamps (day lengthening up to 16 hrs, P.P.F.D. respectively of 1.1 ± 0.1 μmol m-2 sec-1 and 20 ± 2 μmol m-2 sec-1).

Minimum temperature in the greenhouse was 4°C in January. All the cultivars resulted reactive to lighting regimes. Flowering spread over a long period (January-June) in any lighting conditions. Anthesis of the first flower on LD/HI plants was reached 50 days and 33 days earlier than on ND plants and LD plants respectively (average of 7 cultivars). No lighting regime determined flowering on 100% of the plants, but the percentage of flowering plants at the end of the trial was higher under LD/HI lighting. Lighting regimes did not affect the length of the raceme or of the whole stem but the number of floral buds in the raceme decreased under LD/HI. On the whole both daylengths and irradiance appear to be important factors for outlining a production protocol for early flowering of Delphinium 'Pacific Giants' in fall-winter climatic conditions of the mediterranean areas.

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