Activities of nucleases in senescing daylily petals

The activity of nucleases during organ death was investigated using daylily petals (Hemerocallis hybrid cv. Stella d'Oro), in which the processes asso ciated with senescence are rapid and clearly ordered. The number of nuclei with fragmented DNA as well as activities of various nucleases increase bef ore certain other events that are related to senescence. Furthermore, DNA b reakage and activities of nucleases occur earlier when senescence is accele rated by abscisic acid and occur later when senescence is retarded by cyclo heximide. These results suggest that the activities of nucleases contribute to the senescence of daylily petals. Therefore, studying the regulation of nuclease gene expression may be useful for understanding components of the signal transduction system that leads to the death of these organs. (C) 20 00 Editions scientifiques et medicales Elsevier SAS.