Comparison between Ultraviolet Irradiation and Ethylene Effects on Senescence Parameters in Carnation Flowers

The effects of ethylene and ultraviolet (UV) irradiation on parameters of senescence in carnation (Dianthus caryophyllus L. cv White Sim) flowers were characterized and compared.UV irradiation (lambda(max) = 254 nanometers), at fluences above 18 kilojoules per square meter, induced petal in-rolling, similar to that which occurred during natural senescence or after ethylene treatment. Increase in the UV dose from 36 to 54 kilojoules per square meter increased the rate of in-rolling to a maximum. Petal in-rolling was accompanied by increased electrolyte leakage, whether it occurred during natural senescence or was induced by UV irradiation or ethylene.Sucrose uptake by cells, membrane ATPase activity, and membrane lipid fluidity all decreased after UV treatment. These parameters were shown earlier to decline during natural or ethylene-induced senescence.UV irradiation induced ethylene production by the petals only during the period of irradiation. However, silver thiosulfate treatment, which blocks ethylene action, showed that the irradiation effects were not due to the ethylene evolved.On the basis of the above results, we concluded that both ethylene and UV irradiation promote a sequence of reactions in the tissue similar to those of natural senescence. However, UV irradiation initiates a reaction which is independent of that which ethylene initiates.