Leaf senescence is a major concern for postharvest leafy vegetables, as leaves are highly prone to yellowing and nutrient loss, resulting in reduced commercial value and limited shelf-life. This study aimed to investigate the effect of L-cysteine (L-cys) on postharvest Chinese flowering cabbage stored at 20 °C. The results showed that 0.5 g L⁻¹ L-cys treatment effectively slowed leaf senescence by downregulating chlorophyll degradation genes (BrNYC1, BrNOL, BrPPH, BrPAO, BrNYE, and BrSAGs) and senescence marker gene BrSAG12. Moreover, this treatment exhibited positive influence on the nutritional quality of cabbage. Also, L-cys treatment maintained ROS homeostasis, preventing excessive ROS accumulation and lipid membrane oxidation. L-cys treatment also maintained a higher total antioxidant capacity and scavenging rate of •OH and O₂^•−. Additionally, L-cys treatment maintained high levels of ascorbate and glutathione and activated antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) and the expression of the encoding genes. Furthermore, L-cys treatment elevated endogenous H₂S levels, which are correlated with increased L-cysteine desulfhydrase activity and the upregulation of H₂S biosynthesis-related genes. These findings suggest that L-cys can delay leaf senescence by reducing chlorophyll breakdown, maintaining ROS homeostasis, and stimulating endogenous H₂S production.

Postharvest grapes exhibit a limited shelf life due to susceptibility to rot and deterioration, significantly reducing their nutritional and economic value. Sulfur dioxide (SO₂) is a widely recognized preservative for extending grape storage life. This study performed a detailed analysis of ‘Munage’ table grapes treated with SO₂ fumigation, employing transcriptomic and metabolomic approaches. Results indicate that SO₂ fumigation significantly extends the shelf life of grapes, as demonstrated by improved visual quality, reduced decay rates, and increased fruit firmness. We identified 309 differentially accumulated metabolites (DAMs) and 1906 differentially expressed genes (DEGs), including 135 transcription factors (TFs). Both DEGs and DAMs showed significant enrichment of flavonoid-related metabolism compared with the control, and the relative content of four flavonoid metabolites (Wogonin-7-O-glucuronide, Acacetin-7-O-glucuronide, Apigenin-7-O-glucuronide, and Baicalein 7-O-glucuronide) were significantly increased in grapes upon SO₂ treatment, suggesting that SO₂ treatment had a substantial regulatory effect on grape flavonoid metabolism. Importantly, we constructed complex regulatory networks by screening key enzyme genes (e.g., PAL, 4CLs, CHS, CHI2, and UGT88F3) related to the metabolism of target flavonoid, as well as potential regulatory transcription factors (TFs). Overall, our findings offer new insights into the regulatory mechanisms by which SO₂ maintains the postharvest quality of table grapes.