Pulsed Light-Emitting Diodes for a Higher Phytochemical Level in Microgreens

A novel research of pulsed light-emitting diode (LED) lighting versus continuous lighting was conducted by analyzing phytochernical levels in microgreens. Red paid choi (Brassica rapa var. chinensis), mustard (Brassica juncea L.), and tatsoi (Brassica rapa var. rosularis) were grown indoors under HPS lamps supplemented with monochromatic (455, 470, 505, 590, and 627 nm) LEDs total photosynthetic photon flux density (PPFD) of 200 10 pmol m(-2) s(-1), for 16 h day(-1). For pulsed light treatments, the frequerides at 2, 32, 256, and 1024 HZ with a duty cycle of 50% monochromatic LEDs were applied. The results were compared to those under the continuous light (0 Hz) condition in terms of total phenolic content, anthocyanins, and antiradical activity (DPPH). The summarized data suggested that pulsed light affected accumulation of secondary metabolites both-positive and negative in rnicrogreens The significant differences in the response of phytochemicals between. ulsed light at several frequencies and continuous light were determined. The most positive effects of 2, 256, and 1024 Hz fortotal phenolic compounds in mustard under all wavelength LEDs were achieved. The LED frequencies at 2 and 32 Hz were the most suitable for accumulation of anthocyanins in red pak choi and tatsoi. The highest antiradical activity under the treatments of 32, 256, and 1024 Hz in mustard arid under the 2Hz frequency in red pak choi and tatsoi was determined.