Crop Performance and Photochemical Processes Under a UV-to-Red Spectral Shifting Greenhouse: A Study on Aubergine and Strawberry

Light quality is a fundamental factor in greenhouses, since different light wavelengths affect plant photosynthesis and photomorphogenesis differently, they thus affect crop growth and productivity. The aim of this study was to evaluate the effect of an experimental greenhouse cover film with UV-to-Red spectral shifting properties on photosynthesis, plant growth, fruit yield, and the quality of two crops spanning over a year-long cultural cycle: aubergines (Solanum melongena L.), as a spring–summer crop, followed by strawberries (Fragaria × ananassa Duch.), as an autumn–spring crop. Trials were carried out in a multispan greenhouse where two sectors were covered, each one with a different light diffusing polyethylene film: one sector was covered with a UV-to-Red photoluminescent film, doped with a blend of rare-earth elements partially converting the UV solar radiation into Red wavelengths, while a light diffusing polyethylene film was used as the control. At the physiological level, spectral shifting affected the chlorophyll fluorescence parameters related to the photochemistry of photosynthesis, which were found to be positively related to crop yield. Moreover, differential analysis of the fast Chlorophyll a fluorescence transients (or OJIP kinetics) showed that spectral shifting affected different steps of the plant photochemical metabolism.