Edible chrysanthemum, pak-choi, endive, chicory, and lettuce were hydroponically cultured under root-restricted conditions in DFT systems and their growth and nutritional values were investigated. Cylindrical plastic tubes 100 mm tall and 20, 25, and 30 mm in diameter were used for root restriction. Growth of all the species was retarded, as the roots were restricted. Pak-choi and edible chrysanthemum showed the greater reduction in growth compared with chicory and endive. Percentage of dry matter, C:N ratio, and ascorbic acid and anthocyanin contents increased in the root-restricted treatments. Changes in mineral contents as affected by root restriction were not consistent among tested species. Optimized root volumes to improve the nutritional values and to reduce the retarding of growth varied according to species of leafy vegetables. Tubes of Φ25mm × 10cm and Φ30mm × 10 cm gave the best results in chicory, endive, and lettuce, and edible chrysanthemum and pak-choi, respectively. Results indicate that nutritional values of hydroponically cultured leafy vegetables can be improved by root restriction using plastic tubes.
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