Cyclamen (Cyclamen persicum L.) is commercially produced from fall until early spring in greenhouses for sales as common winter and spring flowering potted plants (Dole and Wilkins, 2005). In regions at high latitudes (e.g., greater than 35 °N, which includes Korea, the northern half of the United States, and Europe), the mean photosynthetic daily light integral (DLI) can be a limiting factor in the production of many greenhouse crops during the winter and early spring (Faust, 2003). The DLI delivered to greenhouse crops is typically reduced by 40% or more by greenhouse glazing and structure (Hanan, 1998). Therefore, some greenhouse crops are commercially grown under a mean DLI of less than 5 mol·m−2·d−1 (in December and January) to greater than 25 mol·m−2·d−1 (in April and May) (Korczynski et al., 2002). A common target minimum mean DLI for many greenhouse crops is 10 mol·m−2·d−1 at plant canopy level (Faust, 2003).
Increasing DLI increases biomass accumulation, hastens development, and improves final plant quality in many floriculture crops. For example, increasing DLI decreased time to flower of eight species of bedding plants (Faust et al., 2005), in vinca [Catharanthus roseus (L.) G. Don.; Pietsch et al., 1995], and in petunia (Petunia ×hybrida hort. Vilm.-Andr.; Kaczperski et al., 1991). Days to flower of petunia decreased from 67 to 56 d as DLI increased from 6.5 to 13.0 mol·m−2·d−1 at 20 °C (Kaczperski et al., 1991). A higher DLI increased flower number and size in vinca (Pietsch et al., 1995) and petunia (Kaczperski et al., 1991). In impatiens (Impatiens wallerana L.), plants grown under a DLI of 12 mol·m−2·d−1 had 2.9 more and 0.5 cm larger flowers compared with plants under 5 mol·m−2·d−1 (Faust et al., 2005). Pansy (Viola ×wittrockiana Gams.) had a shorter stem and flower peduncle under a high DLI than a lower one (Niu et al., 2000).
High DLI can increase growth rate by promoting photosynthesis (Nemali and van Iersel, 2004). Increasing DLI increased dry matter and flower and floral bud number in rose yarrow (Achillea ×millefolium L.), gaura (Gaura lindheimeri Engelm. & Gray), lisianthus [Eustoma grandiflorum (Raf.) Shinn], red salvia (Salvia splendens Sell ex Roem. & Schult.), and French marigold (Tagetes patula L.) (Fausey et al., 2005; Islam et al., 2005; Moccaldi and Runkle, 2007). Total dry weight of eight annuals increased, but generally at a decreasing rate, as DLI increased from 5 to 43 mol·m−2·d−1 (Faust et al., 2005). These results suggest that plant developmental rate increases as DLI increases until some threshold beyond which a further increase has little or no effect on developmental rate.
Cyclamen has been classified as a day-neutral plant (Thomas and Vince-Prue, 1997), although some studies indicate that photoperiod, light quality, and light intensity can modify the flowering and subsequent growth of this plant (Erwin et al., 2004; Heo et al., 2003; Neuray, 1973; Widmer and Lyons, 1985). In particular, long days and a high irradiance promoted cyclamen growth and flowering (Cheon et al., 2006; Oh et al., 2008; Rhie et al., 2006). Supplemental lighting from high-pressure sodium lamps at 30 μmol·m−2·s−1 for 20 h per day shortened cultivation time and improved the quality of potted cyclamen (Verberkt et al., 2004).
Previous studies (Cheon et al., 2006; Rhie et al., 2006) showed that an increase in DLI, either by increasing the instantaneous photosynthetic photon flux (PPF) with the same photoperiod, or by extending the photoperiod at the same PPF, promoted growth and flowering of cyclamen. Subsequently, we found in preliminary research that flowering of cyclamen was accelerated by an increase in DLI within a narrow range (Oh et al., 2008). The objective of this study was to investigate the effect of DLI on growth and flowering of cyclamen to assist commercial growers manage light during cyclamen production.
Adams, S.R., Hadley, P. & Pearson, S. 1998 The effects of temperature, photoperiod, and photosynthetic photon flux on the time to flowering of Petunia ‘Express Blush Pink’ J. Amer. Soc. Hort. Sci. 123 577 580
Armitage, A.M., Carlson, W.H. & Flore, J.A. 1981 The effect of temperature and quantum flux density on the morphology, physiology, and flowering of hybrid geraniums Pelargonium ×hortorum J. Amer. Soc. Hort. Sci. 106 643 647
Cheon, I.H., Oh, W., Park, J.H. & Kim, K.S. 2006 Long day and high photosynthetic photon flux promote the growth and flowering of Cyclamen persicum Hort. Environ. Biotechnol. 47 353 358
Dansereau, B., Zhang, Y. & Gagnon, S. 1998 Stock and snapdragon as influenced by greenhouse covering materials and supplemental light HortScience 33 668 671
Erickson, V.A., Armitage, A., Carlson, W.H. & Miranda, R.M. 1980 The effect of cumulative photosynthetically active radiation on the growth and flowering of the seedling geranium, Pelargonium ×hortorum Bailey HortScience 15 815 817
Erwin, J., Mattson, N. & Warner, R. 2004 Light effects on annual bedding plants 62 71 Fisher P. & Runkle E. Lighting up profits Meister Media Worldwide Willoughby, OH
Fausey, B.A., Heins, R.D. & Cameron, A.C. 2005 Daily light integral affects flowering and quality of greenhouse-grown Achillea, Gaura, and Lavandula HortScience 40 114 118
Faust, J.E., Holcombe, V., Rajapakse, N.G. & Layne, D.R. 2005 The effect of daily light integral on bedding plant growth and flowering HortScience 41 114 119
Graper, D.F. & Healy, W. 1990 Synergistic acceleration of Begonia semperflorens development using supplemental irradiance and soil heating Acta Hort. 272 255 259
Graper, D.F. & Healy, W. 1991 High pressure sodium irradiation and infrared radiation accelerate Petunia seedling growth J. Amer. Soc. Hort. Sci. 116 435 438
Heo, J.W., Lee, C.W., Murthy, H.N. & Paek, K.Y. 2003 Influence of light quality and photoperiod on flowering of Cyclamen persicum Mill. cv. Dixie White Plant Growth Regulat. 40 7 10
Islam, N., Patil, G.G. & Gislerød, H.R. 2005 Effect of photoperiod and light integral on flowering and growth of Eustoma grandiflorum (Raf.) Shinn. Scientia Hort. 103 441 451
Kaczperski, M.P., Carlson, W.H. & Karlsson, M.G. 1991 Growth and development of Petunia ×hybrida as a function of temperature and irradiance J. Amer. Soc. Hort. Sci. 116 232 237
Karlsson, M.G. 2002 Flower formation in Primula vulgaris is affected by temperature, photoperiod and daily light integral Scientia Hort. 95 99 110
Karlsson, M.G. & Werner, J.W. 2001b Temperature after flower initiation affects morphology and flowering of cyclamen Scientia Hort. 91 357 363
Kessler, R., Armitage, A.M. & Koranski, D. 1990 Effect of supplemental light and duration of exposure on growth and flowering of Begonia semperflorens Acta Hort. 272 137 144
Korczynski, P.M., Logan, J. & Faust, J.E. 2002 Mapping monthly distribution of daily light integrals across the contiguous United States HortTechnology 12 12 16
Lieth, J.H., Merritt, R.H. & Kohl H.C. Jr 1991 Crop productivity of petunia in relation to photosynthetically active radiation and air temperature J. Amer. Soc. Hort. Sci. 116 623 626
Loehrlein, M.M. & Craig, R. 2004 The effect of daily light integral on floral initiation of Pelargonium ×domesticum L.H. Bailey HortScience 39 529 532
Moccaldi, L.A. & Runkle, E.S. 2007 Modeling the effects of temperature and photosynthetic daily light integral on growth and flowering of Salvia splendens and Tagetes patula J. Amer. Soc. Hort. Sci. 132 283 288
Mortensen, L.M. & Moe, R. 1995 Effects of temperature, carbon dioxide concentration, daylength, and photon flux density on growth, morphogenesis, and flowering of miniature roses Acta Hort. 378 63 70
Nemali, K.S. & van Iersel, M.W. 2004 Light effects on wax begonia: Photosynthesis, growth respiration, maintenance respiration, and carbon use efficiency J. Amer. Soc. Hort. Sci. 129 416 424
Niu, G., Heins, R.D., Cameron, A.C. & Carlson, W.H. 2000 Day and night temperatures, daily light integral, and CO2 enrichment affect growth and flower development of pansy (Viola ×wittrockiana) J. Amer. Soc. Hort. Sci. 125 436 441
Oh, W. 2007 Growth mechanism and its manipulation by temperature, light intensity, and plant growth regulators in Cyclamen persicum PhD diss. Seoul Natl. Univ Seoul, Korea
Oh, W., Rhie, Y.H., Park, J.H., Runkle, E.S. & Kim, K.S. 2008 Flowering of cyclamen is accelerated by an increase in temperature, photoperiod, and daily light integral J. Hort. Sci. Biotechnol. 83 559 562
Pietsch, G.M., Carlson, W.H., Heins, R.D. & Faust, J.E. 1995 The effect of day and night temperature and irradiance on development of Catharanthus roseus (L.) ‘Grape Cooler’ J. Amer. Soc. Hort. Sci. 120 877 881
Pramuk, L.A. & Runkle, E.S. 2005a Modeling growth and development of Celosia and Impatiens in response to temperature and photosynthetic daily light integral J. Amer. Soc. Hort. Sci. 130 813 818
Pramuk, L.A. & Runkle, E.S. 2005b Photosynthetic daily light integral during the seedling stage influences subsequent growth and flowering of Celosia, Impatiens, Salvia, Tagetes, and Viola HortScience 40 1336 1339
Rhie, Y.H., Oh, W., Park, J.H., Chun, C. & Kim, K.S. 2006 Flowering response of ‘Metis Purple’ cyclamen to temperature and photoperiod according to growth stages Hort. Environ. Biotechnol. 47 198 202
Sonneveld, C. & Starver, N. 1992 Nutrient solution for vegetables and flowers grown in water or substrates. Serie Voedingsoplossingen Glastuinbouw, No. 8 42 Naaldwijk The Netherlands
Verberkt, H., Heins, R.D. & Blom, T. 2004 Supplemental lighting on potted plants 72 78 Fisher P. & Runkle E. Lighting up profits Meister Media Worldwide Willoughby, OH
White, J.W. & Warrington, I.J. 1984 Growth and development responses of geranium to temperature, light integral, CO2, and chloromequat J. Amer. Soc. Hort. Sci. 109 728 735