Effect of LED Lighting Regime on Quality of Pak Choi (Brassica rapa subsp. chinensis) During Cold Storage

Light combined with refrigeration is an effective strategy for preserving postharvest fruit and vegetable quality. This study explored the effects of various red–blue (R/B) light-emitting diode (LED) light/dark (L/D) cycles on pak choi during refrigeration. Pak choi exposed to a 4/20 h L/D cycle exhibited greater freshness, along with the highest levels of total phenolic compounds, chlorophyll, and ascorbic acid, particularly after 6 days of refrigeration. Transcriptomic analysis showed that this lighting regime upregulated genes associated with phenylpropanoid and flavonoid biosynthesis (PAL, C4H, ANS, CHS, FLS) and ascorbate metabolism (VTC2_5, VTC4, APX), boosting phenolic and ascorbic acid content. It also reduced chlorophyll degradation by increasing the expression of genes in the porphyrin metabolism pathway (CRD1, POR, DVR). These findings highlight the benefits of R/B light with a 4/20 h L/D cycle for enhancing pak choi quality during refrigeration storage. This approach provides an efficient approach for vegetable preservation.