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ISHS Acta Horticulturae 1107: XXIX International Horticultural Congress on Horticulture: Sustaining Lives, Livelihoods and Landscapes (IHC2014): International Symposium on Innovation and New Technologies in Protected Cropping

The role of blue light in night-interruption lighting of petunia

Authors:   Qingwu Meng, E.S. Runkle
Keywords:   far-red light, floriculture crops, flowering, LEDs, light-emitting diodes, photoperiodic lighting, red light
DOI:   10.17660/ActaHortic.2015.1107.13
A combination of red (R, 600-700 nm) and far-red (FR, 700-800 nm) light during the night (night interruption, NI) promotes flowering of long-day plants, but the relevance of blue (B, 400-500 nm) light with R and/or FR light is not well understood. We investigated the use of different light-emitting diodes (LEDs) to regulate flowering of two petunia cultivars [Petunia hybrida LSQUOWave Purple ClassicRSQUO (WPC) and LSQUOWave Purple ImprovedRSQUO (WPI)] grown at a constant 20C. In addition to a 9-h short-day control, 4-h NI treatments were delivered from incandescent (INC) lamps or five LED combinations: B, B+R, B+FR, B+R+FR, and R+FR. The photon flux of all NIs from 400 to 800 nm was 1.3-1.7 μmol m-2 s-1 at plant height, and the treatments with multiple wavebands delivered equal photon flux of each color. Date of first open flower and stem length at flowering were recorded. For both cultivars, the INC, B+R+FR, and R+FR NIs accelerated flowering the most, whereas the B NI was not perceived as a long day. The B+R and B+FR NIs were as effective as the INC NI for petunia WPI. In contrast, flowering of petunia WPC was delayed under the B+R and B+FR NIs compared with the B+R+FR NI. Stem length of both cultivars was not affected by B light. We conclude that as low-intensity NI lighting, B light alone, or when added to R and FR light, did not influence flowering or extension growth of petunia.

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