ABSTRACT
In a natural population of trees, seed yield depends upon: the age and size structure of the population, abundance with which reproductive structures are initiated and subsequently develop, pollination effectiveness, fertilization effectiveness, the success of resulting seed development, and the degree of predispersal predation. Therefore, in learning about tree fecundity, these conditions may be fruitfully considered as seed yield components. The detailed work of R. Sarvas with Pinus silvestris is a good example of this comprehensive approach to the study of seed production. Whatever the physiological mechanism, since the degree of dormancy is genetically variable in tree seed, dormancy induction mechanisms are a product of genetic programming. Just as seed size is partly determined by environment, so is the degree of dormancy affected by the parent plant's growing conditions. Most of the data supporting this idea have come from experiments with herbaceous species, but examples of the effect can be seen in work with species from predominandy woody plant families.
