Effect of Nitric Oxide Fumigation Combined with Hypobaric Treatment on the Postharvest Quality and Metabolism of Polyamines and Glutathione in Xiaobai Apricots

To investigate the regulatory effect of nitric oxide (NO) fumigation combined with hypobaric treatment (HYT) on the postharvest quality of Xiaobai apricots, ‘Luntai’ apricots were treated with exogenous NO under hypobaric conditions (HYT + NO). NO fumigation at normal pressure (NO group) and single hypobaric treatment (HYT group) were used as controls for comparison. During 10 days of storage at (25 ± 2) ℃ and (85 ± 5)% relative humidity, changes in fruit firmness, mass loss, decay incidence, antioxidant capacity, and key indicators related to glutathione and polyamine metabolism were measured. Correlation analysis was also performed. The results showed that HYT + NO treatment significantly enhanced the antioxidant capacity of the fruit, maintained higher firmness, and suppressed the increase in mass loss and decay incidence. Meanwhile, HYT + NO up-regulated the expression of genes involved in polyamine and glutathione metabolism, leading to increased activities of arginine decarboxylase, ornithine decarboxylase, spermidine synthase, spermine synthase, S-adenosylmethionine decarboxylase, γ-glutamylcysteine synthetase, glutathione reductase, glutathione peroxidase, and glutathione S-transferase, while decreasing the activities of diamine oxidase and polyamine oxidase. Moreover, this treatment maintained the contents of spermidine (Spd), spermine (Spm), and reduced glutathione (GSH) and mitigated the accumulation of oxidized glutathione and hydrogen peroxide. Correlation analysis revealed that Spd, Spm, and GSH were significantly positively correlated with total antioxidant capacity and firmness, but significantly negatively correlated with mass loss and decay incidence. Spd and Spm were also significantly positively correlated with GSH. In conclusion, HYT + NO treatment enhances the antioxidant capacity and maintains the postharvest storage quality of Xiaobai apricots through the synergistic regulation of the polyamines (PAs) and GSH metabolic pathways.