A. Bruce Downie

Seeds comprise 70% of the human diet world-wide and make up the bulk of the feed used to produce livestock that constitute a considerable proportion of the other 30% of our diet. On a practical level seed longevity and germination are the foundations of modern agriculture. On a fundamental level, seed germination is the stage of the life cycle when the plant undergoes a rapid transition from being most impervious (the seed), to being most susceptible (the seedling) to environmental stress. The orchestration of the switch from seed development to seed maturity and then to the germinative mode each involves a radical alteration of transcriptional and post-transcriptional activity. These alterations result in profound physiological changes that permit most seeds (so called 'orthodox' seeds) to survive dehydration to 5% moisture content, extend longevity in this dry state for considerable periods and finally undergo a fascinating alteration upon imbibition commencing with an intense metabolic activity and culminating in the completion of seed germination and the establishment of the next generation. I examine, at the physiological and molecular level, how the seed thus fulfills its function as a propagule.