Evaluation of UV-B lighting design for phenolic production in kale plants using optical simulation with three-dimensional plant models in plant factories

Although ultraviolet-B (UV-B, 280-315 nm) radiation has been known as an effective elicitor for improving bioactive compound contents in plants, its practical application to plant factories is still in its infancy. This study aimed to develop an evaluation method for optimising the lighting design of UV-B radiation in plant factories. To this end, a prediction model of phenolic content was adapted for kale (Brassica oleracea L. var. acephala) plants grown in a plant factory using an optical simulation in a three-dimensional plant model. The prediction model was calibrated using experimental data with different 310 nm UV-B light-emitting diode (LED) arrangements. UV-B radiation significantly enhanced the total phenolic content, total flavonoid content, UV-B absorbing pigment content, and antioxidant capacity in kale plants. In scenario analysis with variables of lighting system, such as vertical or horizontal lighting distance and lighting angle of UV-B LED, the spatial distribution of phenolic accumulation was estimated using the calibrated model and simulated UV-B radiation interception. Although the uniformity and efficiency were opposite in most scenarios, both values for phenolic production increased with changes in horizontal position. The annual yields per electrical energy consumed for producing total phenolics and flavonoids were expected to improve by 14.2 and 34.0%, respectively, assuming the addition of UV-B LED as the optimal lighting design among the scenarios. These evaluation and optimisation methods using model-based simulations will help to design custom UV-B lighting systems for the production of bioactive compounds in commercial plant factories. (c) 2022 IAgrE. Published by Elsevier Ltd. All rights reserved.