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Programmed
cell death (PCD) is a genetically controlled process that is essential
to the development, differentiation and homeostasis of multicellular organisms.
Apoptosis is the most characterized form of PCD in animals. PCD occurs
in various types of plant cells during development and in response to
environmental stimuli. The PCD that occurs in seed tissues at a specific
post-germinative stage of seedling growth has been most extensively studied
in the aleurone layer cells of cereal grains. The megagametophyte of white
spruce (Picea glauca) seeds is living at seed maturity and is the major
storage organ of the seed. Following germination, the megagametophyte
cells die after the storage reserves are mobilized. We characterize the
programmed death of white spruce megagametophyte cells by examining post-germinative
changes in tissue and cellular morphology, and changes of biochemical
markers (e.g. induction of nuclease and protease activities and DNA fragmentation).
The potential control of cell death by hormone such as ABA, ethylene,
and the mutual regulation of ROS and proteasome are also investigated.
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