The Effect of LED Lighting Durations on Growth, Yield and Quality of Mustard (Brassica juncea L.) under Greenhouse Condition

Light-emitting diodes (LEDs) show promise as a radiation source for intensive crop cultivation systems, especially for vegetables in the greenhouse. Regarding mustard greens, most studies have investigated the effects of LED lights at the seedling stage under chamber conditions for microgreens not addressed throughout their growing period up to harvest. Therefore, this study is focused to evaluate the effect of additional LED lighting time from 6 pm on the growth, yield and quality of mustard greens under a greenhouse in Kien Giang province as a typical tropical region. The experiment was arranged in a completely randomized design with 3 replications, from August 1st to September 18th, 2023. Four treatments: AL0, AL2, AL4 and AL6 correspond to lighting durations of 0, 2, 4 and 6 h of LED light, which includes a combination of 3 white lights: 1 pink light, 58 μmol·m−2·s−1 PPFD, and a Blue (18 %): Green (41 %): Red (41 %) ratio. Results showed that AL4 had the most significant positive impact on mustard plant growth, with higher dry and fresh weight, plant height, leaf width and length. However, AL6 inhibited most parameters except leaf number. Additionally, under AL4 conditions, mustard allocated more biomass to leaves, while those under AL6 conditions allocated more biomass to stems. In terms of quality, LED lighting duration negatively influenced protein content. For instance, AL0 showed the significantly greatest protein value (2.87 ± 0.08 g·kg−1) compared to others. Apart from AL0, AL6 had a considerably higher value of protein content (2.58 ± 0.2 g·kg−1) compared to AL2 (1.74 ± 0.04 g·kg−1) and AL4 (2.17 ± 0.07 g·kg−1). The additional durations of LED lighting influenced mature mustard greens’ morphology, physiology and quality, providing valuable scientific information for improving vegetable quality and quantity in tropical zones. HIGHLIGHTS 4 hours of additional LED light had the most significant positive impact on mustard plant growth, with higher dry and fresh weight, plant height, leaf width, and length. Additionally, leaf number increased under 6 hours of additional LED light. Under 4 hours of additional LED light, mustard allocated more biomass to leaves, while those under 6 hours of additional LED light allocated more biomass to stems. Lighting with LED resulted in a lower protein value, and different durations of LED lighting resulted in varying protein content values. GRAPHICAL ABSTRACT