Flower abscission: environmental control, internal regulation and physiological responses of plants

Many aspects of the abscission process have been reviewed in the past and it has been some time since a review on flower abscission has been published. Recent advances in this field thus permit a consolidation of the current research. The flowering syndrome in plants is an intricate and complex process that ensures survival of the species. As such, it is a strictly controlled and tightly regulated series of developmental events, the success of which is a major priority. Abscission of flowers and floral organs is an important part of the reproductive cycle, that is similarly under exact direction. Flowers may be shed in response to an internal or genetic timing mechanism as well as external factors such as environmental stimuli, pathogen attack and pollination. These cues are processed and converted into physiological responses that include alteration in hormone production, induction and repression of specific signal transduction pathways, activation of existing enzymes and transcription of new proteins. While much progress has been made in identifying components of abscission using mutants and molecular biological approaches, many gaps remain in our understanding, especially in terms of considering abscission and its related events in the light of energy (carbohydrate) supply and demand.