IMPACT OF LIGHT INTENSITY ON FLUCTUATIONS IN GROWTH AND NUTRIENT CONTENT OF LEAFY VEGETABLES UNDER ARTIFICIAL CONDITIONS

The impact of variability in light intensity (photosynthetic photon flux, PPF) at a closed plant factory with artificial light on fluctuations in growth and nutrient content (ascorbic acid, β-carotene, calcium and iron) of 3 types of leafy vegetables was investigated to examine the possibility of nutritional labeling for leafy vegetables. Chingensai (Brassica rapa L. var. chinensis), Komatsuna (Brassica rapa L. var. peruviridis), and Rocket (Eruca vesicaria L.) were cultivated in a hydroponic culture system under artificial conditions (white fluorescent lamps as light source). Four test treatments were established with PPF values of 160, 200, 240, and 280 μmol m^-2•s^-1. Fresh and dry weights were greater with higher PPF values for all plant species. However, no impact of PPF was observed on the dry matter ratio or the proportion of the fresh weight of leaf blades in relation to the total fresh weight of plants. Except for ascorbic acid concentration in Chingensai and β-carotene and iron concentrations in Rocket, no significant differences in nutrient concentrations (fresh or dry weight basis) were revealed in relation to PPF. The coefficient of variation for nutrients was relatively smaller than that of fresh and dry weight in all crops. There were only small fluctuations in nutrient concentrations attributable to variation in PPF in these leafy vegetables, particularly in Chingensai and Komatsuna, which have a uniform shape and growth rate. Thus, nutritional labeling in leafy vegetables cultivated in plant factories is considered possible.