Introduction

The programmed senescence of flower petals is a highly controlled developmental event and plays an important role in the overall reproductive strategy of many plants (see Stead & van Doom, this volume). The flower is a terminally differentiated complex structure composed of many organs performing a variety of functions, the ultimate goal being successful sexual reproduction. These functions include the production of pollen, pollination, fusion of gametes, and the development and dispersal of viable seeds. In many species, the petals function in the attraction of insects for pollination. Consistent with the petals' short-lived role in reproduction, pollination often serves as a signal for the initiation of petal senescence (Stead, 1992). In the flowers of carnation, the phytohormone ethylene serves as a signal for the initiation of petal senescence following pollination (Nichols, 1977; Nichols et al., 1983). In the absence of pollination petal senescence in carnation still occurs and is mediated by the increased production of ethylene (Nichols, 1966; Wang & Woodson, 1989). This paper attempts to summarise recent data on the regulation of programmed organ death in carnation flower petals with a particular focus on the molecular events associated with the induction of senescence by ethylene. It is not intended as an exhaustive review of flower senescence, for which the reader is referred to papers by Borochov and Woodson (1989), Cook and van Staden (1988), and Reid and Wu (1992).