Assessment of nutritional properties of Valerianella locusta growing in indoor vertical farms under different lighting conditions.

One of the biggest challenges of our times is to produce enough food for the increasing population of urban areas. Vertical Farms (VFs) are controlled indoor growing systems that maximize crop production and land-use efficiency. The major disadvantage of VFs is the high energy demand for lighting, making it necessary to adopt light conditions that offer desirable traits to the plants under minimum energy consumption. The aim of this study was to evaluate nutritional factors of corn salad (Valerianella locusta) plants, like ascorbic acid, polyphenol content, antioxidant activity and nitrate concentration under different lighting conditions. Two different light qualities were tested, white and blue-red-near-infrared (B-R-NIR) parts of the spectrum. The treatments had a photoperiod of 16 hours/day of light, and 3 different PPFD values of 150, 250 and 350 μmol m-²s^-1, resulting in different daily light integrals, DLI of 8.6, 14.4 and 20.2 mol m^-2d^-1, respectively. Ascorbic acid concentration was observed steady, at maximum levels during all treatments under B-R-NIR lighting, while under white light reached the peak value under DLI 14.4 mol m^-2d^-1. Polyphenol levels were significantly higher at DLI 8.6 mol m^-2d^-1 under both lighting qualities, while antioxidant activity was significantly higher at DLI 20.2 mol m^-2d^-1 under white light and DLI 8.6 mol m^-2d^-1 under B-R-NIR lighting. Nitrate concentration was at lowest levels at DLI 8.6 mol m^-2d^-1 under both light spectra. As a conclusion, optimal biochemical characteristics of plants were observed at DLI 8.6 mol m^-2d^-1 under B-R-NIR lighting. This condition was also the most energy efficient.