Lamp type and irradiance level for daylength extensions influence flowering of Campanula carpatica 'Blue Clips', Coreopsis grandiflora 'Early Sunrise', and Coreopsis verticillata 'Moonbeam'

摘要

The effectiveness of cool-white fluorescent, high-pressure sodium, incandescent and metal halide lamps for inducing flowering through daylength extensions was tested in 1994-95. Lighting was delivered as a 7-h day extension with photosynthetic photon flux (PPF) ranging from 0.05 to 2.0μmol m-2 s-1 following a 9-h natural daylength. Threshold irradiance values for flowering ranged from <0.05 to 0.4μmol m-2 s-1, depending on the species. Saturation irradiance values for Campanula carpatica cv. BlueClips and Coreopsis grandiflora cv. Early Sunrise were between 0.2±0.2 and 0.7±0.5μmol m-2 s-1, and did not differ between lamps. An irradiance of 1.0μmol m-2 s-1 from any lamp was adequate for flowering in C. verticillata cv. Moonbeam. Time to flowering at irradiances above the saturation points did not differ significantly between lamp types for all species tested. Plants of Campanula carpatica cv. Blue Clips and Coreopsis grandiflora cv. Early Sunrise had significantly longer stems under incandescent lamps than in any other treatment. Stems of C. verticillata cv. Moonbeam grown under cool-white fluorescent lamps were～10% longer than those grown under high-pressure sodium or incandescent lamps.