Nuclear activation during early germination of the higher plant embryo.

Introduction Quiescent and dormant embryos, germination: definitions Nuclear characteristics of the cell population in quiescent embryos Distribution of quiescent embryo cell nuclei in different phases of the cell cycle How is the high G\ cell level of quiescent embryos established? What are the mechanisms controlling G\ cell accumulation? Controversial observations on the high G\ accumulation in quiescent embryos Asynchrony of the first mitotic cycle The problem of dry tissue fixation Ultrastructure and cytochemistry of the nucleus in quiescent and early germinating embryos Shape of the nucleus Chromatin in quiescent embryos Possible factors responsible for chromatin condensation in quiescent embryos Dehydration Ions HistoneHl Poly(ADP-ribose) polymerase Chromatin during early germination Possible relationship between chromatin dispersion and its activity Transcription DNA replication and DNA repair RNP translocation Nucleoplasmic ribonucleoproteins Are nucleoplasmic RNPs the storage form of long-lived mRNAs? The nucleolus Ultrastructure Vacuolation Possible significance of nucleolar RNP loss during early germination