Seeds are a vital component of the world’s diet. Cereal
grains alone, which comprise -90% of all cultivated seeds,
contribute up to half of the global per capita energy intake.
Not surprisingly then, seed biology is one of the most extensively
researched areas in plant physiology. Even in relation
to the topics reviewed here, a casual perusal of the Agricola
database reveals that well over 5000 publications on seed
germination and 700 on seed dormancy have appeared in
the last decade. Yet we still cannot answer two fundamental
questions: how does the embryo emerge from the seed to
complete germination, and how is embryo emergence blocked
so that seeds can be maintained in the dormant state? Obviously,
with such a large literature on the subject, this review
is far from comprehensive. Nevertheless, it provides both an
overview of the essential processes that are associated with
germination and a description of the possible impediments
thereto that may result in dormancy.