DEVELOPING LED LIGHT RECIPES FOR MULTI-LAYERING SYSTEMS: LED AS AN ALTERNATIVE FOR HPS IN FORCING OF RHODODENDRON SIMSII
Recent developments show that Light Emitting Diodes (LED) can most likely not replace High Pressure Sodium (HPS) lights for full production cycles. However, the typical discrete spectral properties of LEDs make them highly suitable for (1) steering plant or flower development at specific growth stages and (2) providing optimal light at close distances to the plant, e.g., in multi-layered systems. We explored this potential to steer flowering induction in the Ghent azalea (Rhodondendron simsii). We developed an optimal light recipe for multi-layered forcing. Rhododendron simsii cultivation necessitates a forcing period in order to obtain intense flower colors and uniform flowering. Forcing requires three weeks 21°C, 70-80% RH and 91 µmol m-2 s-1 light intensity. This means extreme high energy input in winter. HPS lights have a high degree of heat radiation preventing their use in multi-layered systems. Since LEDs seems suitable, to determine the optimal wavelength composition and intensities we compared four LED-units equipped with different amounts of Red, Far-Red and Blue light with conventional HPS lamps and a control. Except for the control, none of the lighting treatments received external sunlight to mimic multi-layered conditions. The experiment was repeated eight times. Measurements indicated increased flower size under additional lighting. All three wavelengths are necessary for optimal flower quality, although red light is of far greater importance then blue light. Light intensities of 91 µmol m-2 s-1 with LED give comparable or even better results than HPS. With LED, the necessary lighting period can be reduced compared to HPS lights. Our results show potential for the use of LED in multi-layered systems for the forcing of azalea, with potential to reduce energy cost remarkably.
Schamp, B., Pauwels , E. and Gobin, B. 2012. DEVELOPING LED LIGHT RECIPES FOR MULTI-LAYERING SYSTEMS: LED AS AN ALTERNATIVE FOR HPS IN FORCING OF RHODODENDRON SIMSII . Acta Hort. (ISHS) 956:121-128
LED assimilation light, forcing, flowering, multi-layering cultivation