Introduction

Senescence is a process usually considered to encompass those events which lead irreversibly to death. However, whilst the term ‘flower senescence’ is frequently encountered, it rarely relates to the flower as a whole but more particularly to those parts of the flower which are regarded as attractive, that is the perianth parts. In fact, as some parts of the flower senesce, other floral organs are still developing. For example, in species exhibiting protrandy, the anthers may well senesce as the stigma expands and becomes receptive to pollination. A further contrast is to be found when petal and leaf senescence are compared; the degeneration of the chloroplast would normally be regarded as senescence in leaves, however, in petals such a process occurs early on and is considered part of the process of petal development.

The process of flower senescence differs greatly from species to species; in some the petals wilt and may eventually abscise, in others abscission of the perianth occurs whilst fully turgid; in yet others a change in colour of all, part, of the perianth portends the ageing process. From this it is clear that both the physiology and structure of the petals undergo changes during senescence. This review endeavours to describe some of the physiological and structural changes that occur in these varied strategies and the factors, particularly pollination, which may initiate the senescence of the perianth parts.