M. Th. de Graaf-van der Zande, T. Blacquière
Experiments were carried out with Euphorbia pulcherrima ‘Angelika’ (poinsettia) and Callistephus chinensis ‘Kometa pink’ (China aster) to investigate the effects of light quality and light level applied during four-weeks of LD treatment on growth and flowering. Eight lamp types were compared for Poinsettia, and six for China aster: incandescent, fluorescent cool white and blue, compact discharge (SL), low pressure sodium (SOX), light emitting diodes (LED, red) and two provisional light sources, far-red and a combination of far-red and fluorescent red. The light levels were applied a gradient from 0.1 μmol m-2s-1 to 2.0 μmol m-2s-1 (400 – 800 nm). The experiments were carried out in 8 greenhouse compartments in autumn 1991 (natural day length max. 13 hours). Light treatments started at sunset and continued until an 18 hour photoperiod had been achieved.

All lamp types were effective for photoperiodic control except for far-red with China aster. Blue was far less effective than the other types for both China aster and Poinsettia. For China aster there was a positive relationship between the level of lighting and the earliness of flowering.

de Graaf-van der Zande, M. Th. and Blacquière, T. (1992). LIGHT QUALITY DURING LONGDAY TREATMENT FOR POINSETTIA AND CHINA ASTER1. Acta Hortic. 327, 87-94
DOI: 10.17660/ActaHortic.1992.327.10
photoperiodic lighting, light quality, elongation, flower induction