DNA fragmentation is regulated by ethylene during carpel senescence in Pisum sativum

Treatment of the pea carpel with the ethylene action inhibitors, silver thiosulphate and 2,5-norbornadiene, retarded its senescence and extended the growth time in which the unpollinated carpel was able to respond to gibberellins. Cells of the senescent carpel have characteristics of apoptotic cells, such as nuclei condensation and internucleosomal DNA fragmentation. Both DNA laddering and condensed nuclei can be prevented by the use of the ethylene action inhibitors, while ethylene treatment accelerates DNA fragmentation. It is postulated that ethylene produced by the flower after anthesis determines the fate of the ovary/ovule; in other words, if the ovary receives no additional stimulus (pollination or gibberellin treatment), it undergoes a senescence process, with some cells showing characteristics similar to those of programmed cell death already identified in animal systems.