Pyrazinamide Improves Vase Quality and Attenuates Ethylene-Associated Senescence in Paeonia Lactiflora ‘coral Sunset’ Cut Flowers

Maintaining vase quality and color stability is a major postharvest challenge for Paeonia lactiflora ‘Coral Sunset’ cut flowers, which show rapid senescence and pronounced petal color fading during vase life. Pyrazinamide (PZA) and related compounds have previously been linked to ethylene-related responses, but their effects on postharvest quality and senescence regulation in cut flowers remain unclear. In this study, cut flowers were treated with 5, 25, 50, 100, and 200 mg·L–1 PZA in a basic preservative solution, and vase performance, water status, flower color, ethylene-associated metabolism, oxidative status, and volatile composition were evaluated. Among the tested concentrations, 50 mg·L–1 PZA showed the most consistent effect, extending vase life by approximately 29 h compared with the basic preservative control (CK2) and 36 h compared with the water control (CK1) under laboratory vase conditions. This treatment helped maintain fresh weight, water balance, and flower diameter during the main ornamental period, and slowed petal color fading, as indicated by higher a* values and lower ΔE* during key vase stages. PZA treatment was also associated with decreased tissue ethylene content, accompanied by altered activities of ethylene-biosynthesis-related enzymes, downregulated expression of PlACS, PlACO, and PlEIN3, enhanced SOD and POD activities, and reduced MDA accumulation. These results indicate that 50 mg·L–1 PZA improved postharvest vase quality under laboratory vase conditions, accompanied by reduced ethylene-associated metabolism and oxidative deterioration. Further validation through ethylene challenge assays, comparisons with established ethylene-management treatments, and residue and safety assessments is required.