1-Methylcyclopropene Inhibits Enzymatic Browning in Lanzhou Lily Bulbs: Involvement of the Ascorbate-Glutathione Cycle in Antioxidant Regulation and Membrane Stabilization.

To address the issue of scale browning in Lanzhou lily bulbs during postharvest storage, this study evaluated the efficacy of 1-methylcyclopropene (1-MCP), a strategy not previously reported for this crop. Treatment with 1.5 μL L-1 1-MCP effectively alleviated scale browning, as evidenced by reduced respiratory rate, lower weight loss, retained bulb firmness, and intact cellular structure. Mechanistically, likely by interfering with ethylene perception, 1-MCP enhanced the lily bulbs' inherent antioxidant capacity by increasing the activities of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, and peroxidase, alongside elevating the contents of ascorbic acid, total phenolics, reduced glutathione, and flavonoids. This treatment downregulated lipoxygenase activity, inhibiting oxidative degradation of membrane unsaturated fatty acids and alleviating membrane lipid peroxidation cascades. It also attenuated superoxide anion generation and diminished hydrogen peroxide accumulation, relieving oxidative stress induced by reactive oxygen species. Significant reductions in malondialdehyde levels and electrolyte leakage further confirmed enhanced cellular membrane stability. Correlation analysis subsequently verified significant intrinsic associations between antioxidant system components, browning inhibition, and quality preservation. Overall, 1-MCP delayed postharvest browning and improved storage quality in Lanzhou lily bulbs, with the ascorbate-glutathione cycle playing an important contributory role in the antioxidant regulatory network, alongside reducing ROS-induced membrane lipid peroxidation and preserving membrane integrity. This offers a physiology-guided strategy for preserving bulb vegetables.