Pulse-treatments with thidiazuron and melatonin improve quality and prolong vase-life of Ranunculus asiaticus L. cut flowers

The buttercup (Ranunculus asiaticus L.), belonging to Ranunculaceae family, is a popular ornamental plant in the Mediterranean area, cultivated and sold as cut flower and potted plant. Loss of postharvest ornamental value in R. asiaticus L. commodities/ product is mainly related to senescence process which appear first in the leaves (yellowing) and subsequently affects the flower (wilting and abscission). Its vase life is quite short and ranges from 9 to 11 days, depending on postharvest conditions. In these experiments, the effects of thidiazuron (TDZ), a synthetic cytokinin-like activity and melatonin (MEL), a recently discovered phytohormone was investigated on postharvest longevity of cut buttercup flowers. Cut flowers were pulse treated with water (control), 10 µM TDZ, 100 µM MEL, 2.5 or 5 mg L‑1 Se (sodium selenate). All treatments were applied for 24 h (pulse). The effect of treatments was then evaluated by water balance relations, chlorophyll content, chlorophyll a fluorescence, vase life and ethylene production. The water balance relations showed the highest values in TDZ and MEL-treated cut flowers. The photosynthetic performance in the control cut flowers exhibited a strong downregulation, whereas the TDZ and MEL treated ones maintained the leaves vitality throughout the experimental timing. The leaf chlorophyll content and ethylene production were both higher in TDZ and MEL treated plant compared to non-treated plant. Both TDZ and MEL treatments showed an improvement of cut flower vase-life. These results suggested that a single 24-h pulse treatment with 10 µM TDZ or 100 µM MEL significantly delayed the progression of senescence process in cut buttercup flowers for more than 18 days.