Different LED Light Spectra Effects on Artemisia Annua in Vertical Farming: Morphological, Physiological, & Environmental

Artemisia annua L. (Sweet wormwood) is a highly valuable medicinal plant known for producing artemisinin, a secondary metabolite and a proven antimalarial agent. However, its cultivation is often restricted due to environmental conditions. This study investigates the effect of different LED light spectra on the cultivation of A. annua aeroponically in vertical farming. The plants were grown with a 31-day cultivation cycle under a photo period of 16/8 hours (light/dark). To examine different LED light spectra, two trials were conducted comparing four different light spectra in each experiment. In the first trial, white light was added to RB1 and RB3 and examined with the same photosynthetic photon flux density (PPFD) of 200 µmol m⁻² s⁻¹. In the second trial, 20% far-red (FR) light was added to the same ratio of red and blue light (RB1 and RB3), and a comparison was made at total PPFD values of 200 and 220 µmol m⁻² s⁻¹. A. annua's morphological and physiological traits and efficiency metrics are investigated. Across both trials, significant regulatory patterns emerged. White light supplementation primarily altered plant growth traits, increased biomass accumulation, and increased artemisinin concentration in the first trial. These results showed that vegetative growth and secondary metabolism were stimulated in parallel. The second trial, however, showed a shift toward regulation mediated by spectral ratios and irradiance. Higher PPFD increased pigment formation and shoot dry matter content and modified leaf structural traits, whereas RB3 with far-red supplementation induced elongation responses and increased the chlorophyll index. Fq’/Fm’ (PSII efficiency) remained physiologically steady despite pigment-related alterations, indicating good photosynthetic acclimation.