Red–Blue LED Light and Plasma-Activated Water Enhance Vindoline and Catharanthine Yields in Catharanthus roseus Grown in a Closed Plant Production System

Madagascar periwinkle [Catharanthus roseus (L.) G. Don] produces vindoline and catharanthine, key precursors used in the semi-synthesis of the high-value anticancer alkaloids vinblastine and vincristine. Closed plant production systems (CPPS) allow precise application of environmental stimuli, including light spectrum and plasma-activated water (PAW). In a previous study, we demonstrated the potential of combining artificial light (white and red) and PAW to enhance the production of these alkaloids in periwinkle grown under controlled CPPS conditions. The present study expands this approach by adopting a more scalable PAW application method and a broader range of LED light spectra to evaluate their effects on vindoline and catharanthine accumulation. After a 37-day pre-treatment under white LEDs in environmentally controlled rooms, plants were subjected to fourteen treatments: phosphor-converted warm white (WW-P, control), red (R), blue (B), red–blue (RB), red–blue–far red (RBFR), phosphor-converted cool white (CW-P), and color-mixed white (W-CM) LED light, each with or without PAW. Plant growth and alkaloid-related responses were assessed at three sampling times: before treatment application (T0), 47 (T1), and 55 (T2) days after pre-treatment. RB produced the highest total vindoline and catharanthine yields [sum of leaf and root yields, with each organ yield calculated as organ dry mass (DM, g plant−1) × organ alkaloid concentration (µg g−1 DM)], reaching 228.0 ± 16.9 and 338.0 ± 27.0 µg plant−1, respectively, which were significantly higher than those obtained under all other light spectra (1.4-fold for vindoline and 1.3-fold for catharanthine relative to WW-P), except for W-CM, for which no significant differences were observed. PAW significantly increased total vindoline and catharanthine yields, reaching 211.0 ± 8.0 and 278.0 ± 11.0 µg plant−1, respectively, corresponding to 1.9- and 1.3-fold increases compared with the untreated condition. Sampling time had a strong effect on total vindoline and catharanthine yields, increasing from 6.0 ± 0.7 and 13.9 ± 1.7 µg plant−1, respectively, at T0, to 258.7 ± 9.8 and 414.0 ± 17.0 µg plant−1, respectively, at T2, corresponding to 43.1- and 29.8-fold increases. In conclusion, the combined use of RB light and PAW, together with harvesting at T2, represented the most effective strategy to achieve high vindoline and catharanthine production, as it enhanced the total yields of both alkaloids.