Growth and morphological responses of gerbera seedlings to narrow-band lights with different light spectral combinations as sole-source lighting in a controlled environment

Abstract

To optimize light-emitting diode (LED) spectral recipes for gerbera (Gerbera jamesonii) seedling propagation, seed germination and seedling morphology, biomass, flowering, and storage quality were observed in four cultivars, ‘Midi Dark Purple’, ‘Majorette Red Dark Eye’, ‘Maxi Pink’, and ‘Maxi White’, under six spectrum treatments: (1) FL, cool white fluorescent light; (2) RB, a photon flux ratio of 85% red and 15% blue (RB-LED); (3) RB + UVB, RB-LED combined with 0.5 μmol·m−2·s−1 of ultraviolet-B; (4) RB + UVA, RB-LED combined with 9.6 μmol·m−2·s−1 of ultraviolet-A; (5) RB + G, a photon flux ratio of 60% red, 15% blue, and 25% green; (6) RB + FR, RB-LED combined with 17.3 μmol·m−2·s−1 of far-red. For all treatments, the photosynthetic photon flux density was 165 μmol·m−2·s−1 under a 16-h photoperiod. Seedling growth and morphology were similar under FL and RB for all cultivars, except for a wider canopy of ‘Majorette Red Dark Eye’ under RB. Each of the tri-chromatic light treatments (i.e., RB + UVB, RB + UVA, RB + G or RB + FR) showed similar effects as RB, except for thicker ‘Maxi Pink’ stems under RB + FR. Furthermore, the quality index, an integrated evaluation of seedling quality, was similar under all the treatments for each cultivar. Given the similar seedling quality and the advantages of LEDs, RB-LED can potentially replace FL for controlled-environment gerbera seedling production, but the tri-chromatic lights tested in this study appear to be unnecessary.