Differential respiratory and morphological responses of carnations pulsed or continuously treated with silver thiosulfate

Abstract

The effect of pulse or continuous silver thiosulfate treatment of cut carnation flowers ( Dianthus caryophyllus L. cv. Elliott's White) on ethylene action was investigated. Flowers were treated either with a 2.0 mM silver thiosulfate 2 h pulse or continuously with 0.2 mM silver thiosulfate and exposed to 0.1–10.0 μl l −1 ethylene. Reciprocally, flowers pulsed with 0.5, 1.0, or 2.0 mM silver thiosulfate were treated with either 4.0 or 8.0 μl l −1 ethylene. Petal tissues were separated into basal and apical segments and assayed for silver ions by atomic absorption spectrophotometer. Although increased respiration occurred in flowers pulsed with 1.0 or 2.0 mM silver thiosulfate, no morphological changes symptomatic of floral senescence accompanied this increase. Flowers continuously treated with 0.2 mM silver thiosulfate exhibited no morphological or respiratory responses to any concentration of exogenous ethylene, whereas both a respiratory increase and irreversible petal wilting were observed in flowers pulsed with 0.5 mM silver thiosulfate. Best fit regression analysis of this data suggests that the interaction between silver ions and ethylene is competitive. The differential distribution of silver ions between basal and apical regions of pulsed or continuously treated petals indicates that the petal base may play an important role in regulating carnation petal senescence.