Exogenous Sugars Involvement in Senescence and Ethylene Production of Tree Peony 'Luoyang Hong' Cut Flowers

Sugars play important roles in petal senescence of cut flowers. In the Expt. 1 of this study, the effects of different concentrations of glucose (60, 90, and 120 g.L-1) and sucrose (30, 60, and 90 g.L-1) application on the vase life, rate of flower diameter increase, rate of flower weight increase and ethylene production of cut tree peony (Paeonia suffruticosa 'Luoyang Hong') were evaluated. At the earlier stage, treatments of different concentrations of glucose and sucrose all retarded the process of flower opening and inhibited the increase of flower diameter and weight, while senescence of flowers fed with different concentrations of glucose was delayed at later stage. Flowers treated with 90 g.L-1 glucose displayed the longest vase life, which showed significant difference (P < 0.05) from those of flowers with the control and sucrose treatments. All treatments with glucose or sucrose not only retarded the decrease of flower diameter and weight, but also suppressed the ethylene production at the earlier stage and delayed the peak of ethylene evolution. In order to study the effect of exogenous sugar on the postharvest response of cut tree peony to ethylene, Expt. 2 was conducted. Cut flowers were treated with. 90 g.L-1 glucose for 4 hours before (GE) or after (EG) exposed to 10 mu-L-1 ethylene for 4 hours. Generally, the opening process of flowers with GE and EG treatments was similar to that of the control, however GE treatment delayed flower senescence. Both GE and EG treatments improved flower diameter and weight, and GE treatment delayed the time of flower weight decrease. Besides, GE delayed climacteric ethylene evolution for 8 hours. All above suggest that exogenous sugars delay tree peony 'Luoyang Hong' cut flower senescence and extend flower vase life through their roles in the decrease of water loss and the suppression of sensitivity to ethylene and ethylene production.