In Canada, as in other northern regions, there is not enough natural light for production of many greenhouse commodities during the darker months of the year (i.e., October through February). In these regions, it is necessary for growers of year-round commodities, such as cut gerbera, to use SL to meet their crops’ economic minimum lighting requirements. Until recently, the only viable options for SL were high-intensity discharge (HID) systems such as HPS lamps. LED technology has improved significantly in recent years, with numerous proven horticultural applications in assimilation (both as SL in greenhouses and as sole-source lighting in growth chambers), photoperiodic, and photomorphogenic lighting (Nelson and Bugbee, 2014; Lopez and Runkle, 2017; Mitchell et al., 2015; Morrow, 2008). LEDs offer the promise of providing energy-efficient, wavelength-specific light in long-lasting fixtures (i.e., >50,000 h). Owing to their unique ability to modify the intensity of individual wavebands of light, LED fixtures can be customized to provide varying spectral recipes, potentially increasing quantum efficiency as well as providing greater plasticity for photoperiod and photomorphological control within a single fixture (Bourget, 2008). Morrow (2008), Pinho et al. (2012) and Currey and Lopez (2013) discussed many relevant horticultural considerations of both HPS and LED technologies.
Many commercially available horticultural LED systems are marketed as a direct replacement for conventional overhead HID greenhouse lighting systems. LED systems are often marketed as requiring 30% to 60% less electricity as HID systems to elicit the same photosynthetic effect on a crop. This is due to potentially higher efficacy (i.e., efficiency of converting electricity into light) and sole production of targeted wavelengths of blue (B, 400 to 500 nm) and red (R, 600 to 700 nm) light that closely match the maximum absorption bands for chlorophyll (McCree, 1972). Conversely, much of the radiation generated by HID systems falls in the green (G, 500 to 600 nm) region or outside of the PAR region altogether (Bergstrand et al., 2016). Therefore, LED-generated PAR may be more efficiently used in many horticultural production scenarios.
Most of the greenhouse-based LED scientific research has, thus far, focused on edible (Dueck et al., 2012; Gomez et al., 2013; Hernandez and Kubota, 2015; Martineau et al., 2012; Poel and Runkle, 2017) and potted floriculture commodities (Currey and Lopez, 2013; Poel and Runkle, 2017; Randall and Lopez, 2014). Many of these studies are over short time periods, either investigating a fast-growing crop (e.g., lettuce) or young plants (e.g., seedling development). Typically, these studies use consecutive replication strategies (i.e., treatments replicated over time), which can result in vastly different natural lighting conditions between replications. Moreover, many studies appear to have relied on fixed experimental plot locations for their treatments (i.e., treatment locations are not randomized between replications), which may not give proper consideration to varied environmental conditions that can occur within a greenhouse environment.
A largely untested application for horticultural LEDs is in the production of high-value cut flowers, where they could be used for assimilation, photoperiod, and photomorphological control depending on the crop, geographic region, and the time of year. The objective of this study was to determine whether LED SL can be used to replace HPS SL in cut gerbera production during the normal SL season in Ontario, Canada, by comparing harvest and postharvest metrics of crops growing under equivalent supplemental PPFD (µmol·m−2·s−1) in a concurrently replicated greenhouse trial.
Bergstrand, K.-J., Mortensen, L.M., Suthaparan, A. & Gislerød, H.R. 2016 Acclimatisation of greenhouse crops to differing light quality Scientia Hort. 204 1 7
Currey, C.J. & Lopez, R.G. 2013 Cuttings of Impatiens, Pelargonium, and Petunia propagated under light-emitting diodes and high-pressure sodium lamps have comparable growth, morphology, gas exchange, and post-transplant performance HortScience 48 428 434
De Silva, W.A.N.T., Kirthisinghe, J.P. & Alwis, L.M.H.R. 2013 Extending the vase life of gerbera (Gerbera hybrida) cut flowers using chemical preservative solutions Trop. Agricultural Res. 24 375 379
Dueck, T.A., Janse, J., Eveleens, B.A., Kempkes, F.L.K. & Marcelis, L.F.M. 2012 Growth of tomatoes under hybrid LED and HPS lighting Acta Hort. 952 335 342
Gomez, C., Morrow, R.C., Bourget, C.M., Massa, G.D. & Mitchell, C.A. 2013 Comparison of intracanopy light-emitting diode towers and overhead high-pressure sodium lamps for supplemental lighting of greenhouse-grown tomatoes HortTechnology 23 93 98
Hernandez, R. & Kubota, C. 2015 Physiological, morphological, and energy-use efficiency comparisons of LED and HPS supplemental lighting for cucumber transplant production HortScience 50 351 357
Lopez, R. & Runkle, E.S. 2017 Light management in controlled environments. Meister Media Worldwide, Willoughby, OH
Martineau, V., Lefsrud, M. & Nanzin, M.T. 2012 Comparison of light-emitting diode and high-pressure sodium light treatments for hydroponics growth of Boston lettuce HortScience 47 477 482
Mitchell, C.A., Dzakovich, M.P., Gomez, C., Lopez, R., Burr, J.F., Hernández, R., Kubota, C., Currey, C.J., Meng, Q., Runkle, E.S., Bourget, C.M., Morrow, R.C. & Both, A.J. 2015 Light-emitting diodes in horticulture. p. 1–87. In: J. Janick (ed.). Horticultural Reviews, Vol. 43. Wiley, New York, NY
Nelson, J.A. & Bugbee, B. 2014 Economic analysis of greenhouse lighting: Light emitting diodes vs. high intensity discharge fixtures PLoS One 9 6 e99010 doi: 10.1371/journal.pone.0099010
Poel, B.R. & Runkle, E.S. 2017 Seedling growth is similar under supplemental greenhouse lighting from high-pressure sodium lamps or light-emitting diodes HortScience 52 388 394
Randall, W. & Lopez, R.G. 2014 Comparison of supplemental lighting from high-pressure sodium lamps and light-emitting diodes during bedding plant seedling production HortScience 49 589 595
Safa, Z., Hashemabadi, D. & Kaviani, B. 2012 Improving the vase life of cut gerbera (Gerbera jamesonii L. cv. ‘Balance’) flower with silver nano-particles Eur. J. Expt. Biol. 2 2489 2492
Sirin, U. 2011 Effects of different nutrient solution formulations on yield and cut flower quality of gerbera (Gerbera jamesonii) grown in soilless culture system Afr. J. Agr. Res. 6 4910 4919