Reproduction and reproductive irregularities of Abies lasiocarpa and A. grandis

Abstract

The initiation of potentially reproductive buds, microsporangiate and megasporangiate, takes place annually and is probably independent of environmental factors. Subsequent development is controlled by year-to-year environmental variation and ultimately determines the presence or absence of the buds. Determination of sexual or vegetative function of the buds is a gradual process during which the function may change. Abortion may take place at any time before the function of the bud is determined as well as during the development of reproductive structures.