Abstract
Summary: Senescence of the higher plant is genetically programmed as the last stage of the development. As the first step to clarify the whole mechanism of senescence, we characterized the pattern of senescence at both the tissue and cellular levels. The coleoptile of rice, which has a short life span and a simple structure, has been used mainly as the material for this study. A series of morphological analyses revealed two different types of programmed cell death in the coleoptile; natural senescence and aerenchyma formation. Although the progression at the tissue level differed largely between two types of death, initial and last events at cellular level were highly conserved in both processes. These facts suggest that the program of cell death would be identical in all cells of the coleoptile and the progression of the program would be affected largely by the surroundings.