The semi-thin sections or ultra-thin sections were made by resin embedding technique using the upper region of the dying stem of AtRabD2b-cosuppressed plant.The sections were observed using light microscope or transmission electron microscopy (TEM) to study the cellular process of the stem death.The results indicated that:(1)The death was firstly initiated from several periphery epidermal cells,and then spread from cell to cell both laterally and longitudinally throughout the whole stem section.(2)Several abnormal phenomenons such as the condensation and peripheral location of chromatin,the decrease of the numbers of internal thylakoid membranes of chloroplast and the autophagy of organelles by vacuole were observed.These features revealed that PCD occurs in the dying cells of the mutant apical stem.It also suggested that AtRabD genes are essential for the cell survival in the apical stem.