THE ROLE OF ETHYLENE IN FLOWER SENESCENCE
Senescence can be broadly defined as those events leading to death of cells, tissues, or organs. Such a definition, applied to cut flowers, might include adverse water relations and floret abscission. Although ethylene probably plays a role in these processes, this review will consider only the stricter sense of senescence, the actual events occurring during aging and death of floral tissues.
Ethylene, a simple hydrocarbon gas, is an important natural regulator of many phases of plant growth and development (reviewed in Reid, 1987). One of the earliest known responses of plants to ethylene was the observation of "sleepiness" of carnation flowers in greenhouses contaminated with ethylene from faulty heaters or leaky gas pipes. At first, ethylene was considered to be a plant growth regulator only; its hormonal role was not established until the development of analytical methods sufficiently sensitive to measure the minute quantities produced by plant tissues. Studies over the past 20 years have provided considerable information on the role of ethylene in flower senescence. This review will briefly summarize these contributions.