Methane-Rich Water Extends Vase Life of Cut Lisianthus: Possibly Involves Nitric Oxide Signaling in Reestablishment of REDOX Homeostasis and Suppression of Ethylene Production

Lisianthus (Eustoma grandiflorum) is a commercially important cut flower with a short postharvest life. This study investigated whether methane-rich water (MRW) could extend its vase life and explored the underlying mechanisms. Cut lisianthus flowers were treated with MRW at concentrations ranging from 0.13 to 1.30 mM, and physiological and biochemical parameters were measured. The results showed that MRW extended vase life in a non-monotonic, dose-dependent manner, with a maximal effect at 0.65 mM (42.43% increase over the control), comparable to 1.04 mM but declining at 1.30 mM. MRW also maintained flower diameter and water content. These physiological improvements were accompanied by higher nitric oxide (NO) levels and a slower decline in nitrate reductase (NR) activity. Pharmacological assays using an NO scavenger and an NR inhibitor partially reversed the effects of MRW, while an NO donor partially mimicked them, suggesting that NR-associated NO accumulation may contribute to the observed responses. Further analysis revealed that MRW coincided with enhanced antioxidant enzyme activities, reduced ROS accumulation, and suppressed ethylene production. Together, these findings suggest that MRW induces NO accumulation that is at least partly associated with NR activity, and this process correlates with enhanced antioxidant defenses and suppressed ethylene biosynthesis.