Gerbera, Gerbera jamesonii from the Asteraceae family is one of the most important cut flowers in the world. quality cut flowers production is especially important. Therefore, the number of flowers, flower color, diameter and length of the flowering stem, flower diameter and post-harvest life (vase life) of the gerbera have been very much considered. This study was carried to investigate the effect of the pre-harvest application of nitric oxide (NO), as sodium nitroprusside (), on quantitative and qualitative characteristics and vase life of ‘Stanza’ cultivar of gerbera. In the first experiment (In the pre-harvest experiment), after plant establishment, the plants were sprayed with concentrations of 0, 50, 100, 200 and 400 ?M sodium nitroprusside at two different times (with one-month intervals) in the flower induction stage. This experiment was conducted as a randomaized completely block design with five treatments and four replications (four pots in each replication). In the second experiment, the gerbera cut flowers were transferred to distilled water and 3% sucrose and to five treatments of concentration of 200 mg/l, 8-hydroxyquinoline and 3% sucrose. The second experiment (after harvest experiement) was conducted as a completely randomized design with six treatment and four replications (three pots in each replication) in two harvesting times. Based on the results of the pre-harvest test, it was determined that twice sodium nitroprusside solubilization increased the number of flowers, stem diameter, flower diameter, leaf relative water content, total chlorophyll content and petal anthocyanin content. Stem diameter, relative water content, ion leakage and ACC oxidase activity were increased in 100 and 200 ?M concentration of , control and control treatment, respectively. The lowest ACC oxidase activity was obtained at 200 ?M and the lowest ionic leakage was observed at 100 ?M sodium nitroprusside concentration. The results of the post-harvest experiment showed that second harvesting time, which was done after two spraying, had increased the relative percentage of fresh weight of gerbera on days 3 and 6, but there was no significant difference between once and twice spraying on day 9. Relative percentage of fresh weight of the gerbera cut flower increased in 3, 6 and 9 days at cut flowers treated with 200 mg/l concentration of 8-hydroxyquinoline sulfate, distilled water and 3% sucrose. The highest ACC oxidase activity was observed in the control treatment and the lowest in 100 and 200 ?M sodium nitroprusside concentrations. The results of this study showed that application of 200 ?M sodium nitroprusside before flower harvest and then placing the flowers harvested in distilled water and 3% sucrose was the most suitable treatment for decreasing activity of ACC oxidase and increasing the vase life of gerbera cut flower. Key words : Gerbera cut flower, Nitric oxide, Sodium nitroprusside, 8-hydroxyquinoline sulphate, Vase life
