Physiological and biochemical responses associated with naturally occurring elicitors and conventional chemical preservatives during the postharvest longevity of cut Rosa hybrida cv. ‘Black Magic’

Postharvest senescence limits the commercial value of cut roses ( Rosa hybrida ). This study evaluated naturally occurring effects of compounds and conventional preservatives in delaying senescence and maintaining postharvest quality of Rosa hybrida cv. ‘Black Magic’. Cut flowers were maintained at 25 ± 2 °C and 60 ± 5% RH in solutions of distilled water (control), γ-aminobutyric acid (GABA, 1 mM), salicylic acid (150 µM), citric acid (150 mg L⁻¹), 8-hydroxyquinoline citrate (HQC, 0.45 mM) + 2% sucrose, or S-carvone (0.60 mM). Physiological and biochemical parameters were measured at day 12, while vase life was monitored continuously. Among treatments, GABA produced the strongest response, extending vase life by 69.7% relative to the control. At day 12, GABA-treated flowers retained 30.6% higher relative water content and 16.4% greater water uptake, while reducing electrolyte leakage by 22.8%, malondialdehyde by 41.9%, hydrogen peroxide by 60.4%, and 1-Aminocyclopropane-1-carboxylic acid levels by 56.0%. Furthermore, GABA upregulated antioxidant defenses, increasing superoxide dismutase, catalase, and ascorbate peroxidase activities by 33.9%, 181.4%, and 82.1%, respectively, while suppressing browning enzymes (polyphenol oxidase and peroxidase decreased by 42.4% and 44.9%). Salicylic acid showed the second-best efficacy, extending vase life by 59.5% with improved membrane stability. Exploratory principal component analysis, clustering, and correlation analyses confirmed clear separation between treatments and the control, strongly associating quality traits with antioxidant capacity. These findings quantitatively identify GABA as a highly effective postharvest preservative for cut ‘Black Magic’ roses, though multi-cultivar validation is recommended prior to commercial application.