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.
BergstrandK.-J.MortensenL.M.SuthaparanA.GislerødH.R.2016Acclimatisation of greenhouse crops to differing light qualityScientia Hort.20417
CurreyC.J.LopezR.G.2013Cuttings of Impatiens, Pelargonium, and Petunia propagated under light-emitting diodes and high-pressure sodium lamps have comparable growth, morphology, gas exchange, and post-transplant performanceHortScience48428434
De SilvaW.A.N.T.KirthisingheJ.P.AlwisL.M.H.R.2013Extending the vase life of gerbera (Gerbera hybrida) cut flowers using chemical preservative solutionsTrop. Agricultural Res.24375379
GomezC.MorrowR.C.BourgetC.M.MassaG.D.MitchellC.A.2013Comparison of intracanopy light-emitting diode towers and overhead high-pressure sodium lamps for supplemental lighting of greenhouse-grown tomatoesHortTechnology239398
HernandezR.KubotaC.2015Physiological, morphological, and energy-use efficiency comparisons of LED and HPS supplemental lighting for cucumber transplant productionHortScience50351357
LopezR.RunkleE.S.2017Light management in controlled environments. Meister Media Worldwide Willoughby OH
MartineauV.LefsrudM.NanzinM.T.2012Comparison of light-emitting diode and high-pressure sodium light treatments for hydroponics growth of Boston lettuceHortScience47477482
MitchellC.A.DzakovichM.P.GomezC.LopezR.BurrJ.F.HernándezR.KubotaC.CurreyC.J.MengQ.RunkleE.S.BourgetC.M.MorrowR.C.BothA.J.2015Light-emitting diodes in horticulture. p. 1–87. In: J. Janick (ed.). Horticultural Reviews Vol. 43. Wiley New York NY
NelsonJ.A.BugbeeB.2014Economic analysis of greenhouse lighting: Light emitting diodes vs. high intensity discharge fixturesPLoS One96e99010doi: 10.1371/journal.pone.0099010
PoelB.R.RunkleE.S.2017Seedling growth is similar under supplemental greenhouse lighting from high-pressure sodium lamps or light-emitting diodesHortScience52388394
RandallW.LopezR.G.2014Comparison of supplemental lighting from high-pressure sodium lamps and light-emitting diodes during bedding plant seedling productionHortScience49589595
SafaZ.HashemabadiD.KavianiB.2012Improving the vase life of cut gerbera (Gerbera jamesonii L. cv. ‘Balance’) flower with silver nano-particlesEur. J. Expt. Biol.224892492
SirinU.2011Effects of different nutrient solution formulations on yield and cut flower quality of gerbera (Gerbera jamesonii) grown in soilless culture systemAfr. J. Agr. Res.649104919