HOW LONG SHOULD FLOWERS LIVE

FLORAL longevity, the length of time a flower remains open and functio nal, varies among plant species. Flowers of some species live less tha n one day (morning glory), whereas others live for several weeks (orch ids)(1-3). By viewing floral longevity as a resource allocation strate y(2,4), we now incorporate the study of its evolution into the well de veloped theoretical framework provided by evolutionarily stable strate gy models that address variation in life history(5,6). Flowers must re main open to contribute to plant fitness through ovule fertilization a nd pollen dissemination, when they require resources for respiratory m aintenance and pollinator attraction. Accordingly, floral senescence s hould occur when the expected fitness gain per unit of floral maintena nce investment diminishes to the point,where it becomes more profitabl e to construct a new flower than to maintain an existing one. Our expe rimental evidence supports floral longevity as an adaptation that bala nces rates of pollen receipt and removal against thr cost of floral ma intenance.