Nano-silver pretreatment delays wilting of cut gardenia foliage by inhibiting bacterial xylem blockage

Gardenias (Gardenia jasminoides Ellis var. 'fortuniana') have commercial importance as cut foliage but are prone to severe postharvest water deficit and quick wilting. Herein, we investigated the efficacy of pretreatment with nano-silver (NS), a strong antibacterial agent, in enhancing water relations and the vase life of cut gardenia foliage. Compared with the deionized-water controls, pretreatment with NS at 10, 15, 20, 25, or 30 mg L-1 for 24 h significantly extended the vase life of cut gardenias. The most effective NS concentration was 15 mg L-1, which promoted the longest (15.2 days) vase life extension, i.e., 310.2% of that of the control treatment. In addition, pretreatment with 15 mg L-1 NS effectively delayed wilting by maintaining a higher water balance value and relative fresh weight when compared with untreated cut foliage. Scanning electron microscopy revealed that these higher values were due to an improved water uptake as a result of the alleviation of bacterial xylem blockage at the stem-ends. Furthermore, Ag concentration was remarkably higher at the stem-ends of NS-pretreated cut gardenias than in any other tissues. Overall, these results demonstrate that NS pretreatment effectively inhibited bacterial growth at the cut stem-ends, and helped maintain a favorable water balance, thereby delaying wilting and extending the vase life of cut gardenias.