Influence of supplementary blue and far-red light on the morphology and texture of Ocimum basilicum L. grown in controlled environments

Authors: OEHLER, MADISON - Oak Ridge Institute For Science And Education (ORISE); KELLY, NATHAN - Oak Ridge Institute For Science And Education (ORISE); Fonseca, Jorge; EVENSEN, ELLA - Oak Ridge Institute For Science And Education (ORISE); Park, Eunhee; Gu, Ganyu; TENG, ZI - Oak Ridge Institute For Science And Education (ORISE); Luo, Yaguang

Submitted to: Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2025
Publication Date: 3/6/2025
Citation: Oehler, M.A., Kelly, N., Fonseca, J.M., Evensen, E., Park, E., Gu, G., Teng, Z., Luo, Y. 2025. Influence of supplementary blue and far-red light on the morphology and texture of Ocimum basilicum L. grown in controlled environments. Horticulturae. 11(3). Article e287. https://doi.org/10.3390/horticulturae11030287.
DOI: https://doi.org/10.3390/horticulturae11030287

Interpretive Summary: Basil is a popular culinary herb grown globally and often cultivated in controlled environments for year-round and local production. Light-emitting diodes (LEDs) used during preharvest can influence plant morphology and metabolism, but research on their effects on basil in fully controlled environments is limited. At the USDA Beltsville Agricultural Research Center, scientists studied the effects of blue and far-red LED treatments, both separately and in combination, on hydroponically grown purple and green leaf basil. They evaluated the harvested leaves for changes in morphology, color, and texture. Blue light increased basil leaf pigmentation and thickness, while far-red light resulted in basil with longer stems and thinner leaves. Despite having thicker leaves when grown under blue light, basil leaves were less tough compared to those grown with far-red light. This study will guide future research on optimizing light conditions to enhance basil growth based on consumer preferences.

Technical Abstract: The rising demand for high-quality basil, combined with its sensitivity to environmental factors position it as an ideal crop for controlled environment agriculture (CEA). Light-emitting diode (LED) technology, which offers improved cost efficiency and precise control over light intensity, spectrum, and duration, has become a staple technology in indoor farms where precise environmental control is necessary. This study investigated the effects of supplemental blue light, far-red light, or a combination of both when added to a broadband white spectrum on Ocimum basilicum L. (basil) biomass accumulation, morphology, and quality (i.e. texture and color). Basil cv. Prospera and Amethyst were grown hydroponically at 28°C and ambient CO2. On day 14 after sowing, 60 µmol·m-2·s-1 of blue (BL), far-red (FR), blue+far-red (BLFR) (1:1), or white light (HW) was added to the base spectrum of white light (LW) for a total of 180 or 240 µmol·m-2·s-1 for the remaining 14 days. The results indicate that supplemental far-red light increased stem length and increased the lightness (L* value) of the leaves of both basil cultivars, while supplemental blue light increased leaf thickness and darkness. Specifically, BL and HW treatments produced leaves that were 17-19% thicker in Amethyst and 18-20% thicker in Prospera compared to the FR treatment. Additionally, FR-treated Amethyst and Prospera basil leaves exhibited greater resistance to puncturing, requiring 1.57 ± 0.43 N and 1.45 ± 0.35 N of force, respectively, compared to 1.19 ± 0.32 N and 1.1 ± 0.21 N under BL treatment. Biomass accumulation was highest in FR treatments for Amethyst and Prospera basil which was 87% and 56% greater than the LW treatment. Basil grown under the BLFR treatment showed results more similar to the FR treatment. These outcomes highlight the potential of customized light recipes in CEA to optimize basil quality, enabling growers to tailor traits such as leaf color, thickness, and toughness to market demands, while also identifying areas for further research to enhance postharvest shelf-life and sensory attributes.