The Effects of Light Intensity on Nitrate and Ascorbic Acid Contents in Green Vegetables, Cultivated in Plant Factories

Abstract

Novel, progressive type of controlled environment horticulture – plant factories enables the precise control of cultivation environment parameters, however, it is not yet well known, how these environmental parameters (lighting, temperature, nutrition etc.) should be balanced seeking for maximal vegetable productivity, optimal internal and external quality. In this study, we present how light emitting diode (LED) light intensity affect nitrate and ascorbic acid contents in different green vegetables, cultivated in the closed environment phytotron. Green and red leaf lettuces (Lactuca sativa ‘Lobjoits green cos’ and ‘Red cos’) and tatsoi (Brassica rapa var. rosularis ‘Rosetto’ F1 were cultivated under combinations of red (660, 638 nm), blue (445 nm) and far-red (735 nm) LED lighting under PPFD of 100-500 μmol m-2s-1. At the stage or technical maturity, nitrate, nitrite contents and ascorbic acid contents were evaluated. The results propose the metabolic interface between nitrates and ascorbic acid in green vegetables, sensitive for lighting intensity. According to WHO, ascorbic acid in green vegetables acts as an antioxidant and neutralize the possible negative effect of nitrate metabolites (nitrites and nitrosamines) for the human organism. Lighting intensities, resulting in low nitrate and high ascorbic acid contents in green vegetables will be elaborated.