Light Down-Conversion Technology Improves Vegetative Growth, Berry Production, and Postharvest Quality in Tunnel-Cultivated Blueberry

This study examined three innovative ‘light-converting films’ that convert green light (−23%) into red light (+8%; Red film), ultraviolet light (−80%) into blue light (+9%; Blue film), and green light (−5.7%) into red light (+4%; Pink film) but also ultraviolet light (−76%) into blue light (+5.6%; Pink film). These films were used for growing blueberry plants under cover under controlled tunnel conditions (27.3 ± 11.7 °C, 51.9 ± 21.6% RH). The use of Red film led to increases in the total plant biomass (+54.2%), and Red and Pink films enhanced the leaf thickness (+17.1% and +14.4%, respectively) as compared to the control (a transparent polyethylene film). No differences in the photosynthetic rate (Pn) were observed at the flowering stage, but a decrease (−25.9%) was observed in plants grown under the Pink film during the green fruit stage. The plants grown under Blue film boosted flower production, leading to +86.8% increase in the total yield. The Blue film improved the total phenolic content (+15.2%) in the fruit, and a +25.3% greater total antioxidant capacity was observed in fruit grown under Pink film. Freshly harvested blueberries were subjected to postharvest experiments (4 °C; in dark conditions; 90–95% RH). The results suggest the importance of Red film in enhancing plant biomass and Red and Blue films in improving fruit yield and maintaining nutraceutical postharvest quality in blueberry fruit.