The Effect of a Sugar-Containing Preservative on Senescence-Related Processes in Cut Clematis Flowers

Abstract

Clematis is a new species grown as cut flower, whose vase life is variable and cultivar-depended. Little is known about senescence of its cut flowers and their response to flower preservatives. The aim of the study was to evaluate the effect of a preservative (standard preservative SP, 8-hydroxyquinoline citrate plus sucrose) or a biocide solution (8-HQC) on certain senescence-related processes in cut clematis flowers. Analyses were done immediately after harvest and at the end of the vase life when control flowers held in water were wilting. A possible relationship between senescence parameters and the vase life of clematis taxa was also sought. As in most cut flowers, the contents of reducing sugars and soluble proteins in clematis petals decreased during the vase life while the proteolytic activity, including that of the cysteine protease, increased and was accompanied by accumulation of free proline and ammonium. Cut flower longevity in cultivars under study was not associated with the initial levels of reducing sugars, soluble proteins or free proline. Neither was the initial proteolytic activity or its increase during vase life related to the vase life itself: cultivars having comparable life spans differed dramatically in the initial and final proteolytic activities. Both solutions containing 8-HQC significantly affected the senescence-related processes and flowers held in them had more soluble proteins and lower proteolytic activity (total, and that of the cysteine protease) than control flowers held in water. Approximately a twofold increase in reducing sugars was observed in flowers held in SP relative to those held in water or in 8-HQC while the accumulation of free proline and ammonium was limited in their petals. This suggests a regulating action of exogenous sugar in senescence of clematis flowers. However, the delay of senescence produced by the preservative was not always associated with a longer vase life in any given cultivar. Further studies are needed to elucidate the role of sugar in clematis flower senescence.