In this study,Ulmus pumila L.seeds were used to investigate characters of nuclear apoptosis,the reactive oxygen species and the activity of caspase-3 after artificially aging at 37℃ and 100% relative humidity (RH) by using confocal laser scanning microscopy (CLSM),DAPI (4′,6-diamidino-2-phenylindole) and TUNEL staining method and caspase-3 detection kit,respectively.The results indicated that the nuclear chromatin appeared to be condensation and shrinkage with the increasing of the ageing time.Some nuclei dissociated into pieces and were released from the cells.The apoptosis was firstly observed in the epidermal cells,and was later found in the cotyledons and hypocotyls.This research also showed the distinct spatial-temporal signature of ROS during ageing coincided with the changes in PCD (programmed cell death) hallmark features,and the signal intensity of Reactive oxygen species (ROS) was gradually increased at 5 d.The activity of caspase was higher in the cytoplasm.Our data indicate that the ROS and caspase-3-like also act as PCD mediators in the process induced by aging.