FLEXIBLE SPECTRA LED ARRAYS FOR SOLE SOURCE LIGHTING AND GROWTH COMPARISONS WITH CONVENTIONAL HIGH PRESSURE DISCHARGE LIGHTING USING ARABIDOPSIS THALIANA

High-power (HP) light emitting diodes (LEDs) offer exciting opportunities for plant lighting research. LED technology now provides intensity levels and wavelengths potentially well suited to study plant growth and development under ‘realistic’, or specific artificially manipulated radiation environments. However, while the ability offered by LEDs to specify precisely the spectral composition provides greater flexibility than conventional broad-spectrum lighting, it also presents significant challenges in characterising what might constitute an ‘optimum’ light spectrum for plant growth. Plant growth and development under custom-designed HP LED arrays, capable of supporting up to 700 LEDs and as many as 10 spectral peaks, were studied within the controlled environment rooms at the New Zealand Controlled Environment Laboratory (NZCEL). White-based and red-blue (RB) based LED spectra, consisting of multitude peaks between 400 and 740 nm, were examined for their potential as sole-source lighting rigs for growing Arabidopsis thaliana. Development rates and biomass were measured from germination to seed set under 200 and 400 µmol m^-2 s^-1 photosynthetically active radiation (PAR), provided by HP LED arrays or the standard high pressure discharge (HID) metal halide and tungsten halogen lighting rig used within NZCEL. Development rate was comparable under the two light sources, but greater biomass obtained under LED suggests an additional potential benefit of LEDs over conventional HID lighting.