Senescence in Plant Development

Abstract

The phenomenon of senescence achieves its most dramatic expression in plants, both as over-all plant senescence and as organ senescence. I believe that this important step in the life cycle of plants is, or can be, a positive force in the ability of the plant species to adapt to limitations of the environment, either climatic or competitive, and that senescence can be a strong factor in the evolutionary adaptability of plants. While the mechanism controlling the more or less sudden onset of plant senescence is obscure, descriptive experiments have established that there are signals from the flowers and fruits which trigger the onset of death. A somewhat parallel situation has been described for the signals controlling the organ senescence of leaves, signals, which in this case come mainly from the stem apex. There is a growing body of evidence suggesting that mobilizing forces are involved in the senescence signals, and in the case of leaf senescence these can be mimicked, at least, through the application of kinetin. It is high time that we should understand more exactly what the physiological cause of plant senescence may be.