Plant senescence. A complex lesson of biology of development

Plant senescence has represented a mystery of biology since 1961, when Carl Leopold sensed the main factors that might control it. The discovery of several hormonal classes gave a precious aid to understand the first mechanisms regulating the phenomenon, which was, in particular, studied in leaf. After the discovery of the molecular bases of genetics, several specialists attempted to connect the hormone activity with the molecular genetic work but only during the 1990s, after the discovery of specific senescence-associate genes, the role of promoting-senescence hormones and retarding-senescence hormones was in good part elucidated, with the help of the plant species Arabidopsis thaliana and its mutants. The history of leaf senescence has had its paradigmatic model in the chlorophyll degradation, a process that remained itself a mystery until 1991, when the products of degradation began being isolated and chemically identified. The research into plant senescence is still the objective of specialists, and represents a very complex problem the integration of which in a unique system appears to be yet far.