Petal senescence is a distinct factor affecting vase-life, which is an important determinant of the quality of cut flowers. Programmed cell death (PCD) is associated with petal senescence, but little is known about the triggering or execution of the process of cell death in petals. In the present study, some features of apoptosis were detected in senescing petals taken from ethylene-insensitive flowers of gladiolus. Agarose gel analysis of DNA extracted from petals revealed that DNA fragmentation, an apoptotic process, occurred in cells of senescing petals. Cytological observation of petal cells suggested that apoptotic changes of nuclei, such as chromatin condensation and nuclear fragmentation, also occurred during cell death leading to petal senescence. Using flow cytometry, we confirmed that nuclear fragmentation correlated with cell death in petals after full flower opening. When the florets were treated with ethylene inhibitors (STS or AOA) or saccharides (sucrose or trehalose), both wilting and nuclear fragmentation of petals were suppressed only by trehalose. From these observations, we conclude that the cell death leading to petal senescence of gladiolus is similar to apoptosis. Furthermore, the present study has provided the first evidence that trehalose has a suppressive effect on apoptotic cell death. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.
