Growth Characteristics and Glucosinolate Levels in Chinese Kale Cultured in a Plant Factory System with Ammonium Sulfate and Light-emitting Diodes

This study investigated the growth characteristics and glucosinolate (GSL) levels of Chinese kale (Brassica oleracea var. alboglabra Bailey 'Jellujon') cultured within a plant factory using different concentrations of ammonium sulfate [(NH4)(2)SO4] and four different light-emitting diode (LED) combinations. In total, 16 combinations of the four (NH4)(2)SO4 concentrations and four LED light sources exerted significantly different effects on plant width, plant height, leaf length, leaf thickness, chlorophyll content, and the number of leaves. For the ratio combination of LED colors using blue light (B), red light (R), and white right (W), B0:R5:W5 showed the best growth characteristics, except for chlorophyll content. The leaf fresh weight (LFW) of Chinese kale did not change significantly with LED treatments, but varied significantly with (NH4)(2)SO4 treatments. S2 and S3 treatments among the (NH4)(2)SO4 treatments resulted in the largest increases in LFW under B0:R5:W5. Six major GSLs were identified, including as sinigrin (SIN), glucobrassicin, gluconapin, 4-OH glucobrassicin, 4-methoxy glucobrasscin, and neoglucobrasscin. The highest total GSL content was achieved with the combination of B0:R5 :W5 and S4, but no significant difference was found among the (NH4)(2)SO4 treatments. For LEDs, B0:R5 :W5 produced the highest total GSL levels. SIN was the dominant GSL under the combination of B0:R5 :W5 and S4. In conclusion, the combination of S4 and B0:R5 :W5 was the most suitable for increasing total GSLs and SIN.