ABSTRACT
The central issue in seed ecophysiology is germination and seedling establishment. Germination consists of three processes: imbibition of water, mobilization and use of food reserves, and growth. J. A. Pitel and W. M. Cheliak have shown how activities of some important enzymes increase during germination in tamarack. At dispersal, conifer seed and many hardwood seed are "dry" due mainly to matric potential. Seed of Quercus and other Fagaceae contain more water. However, the water potential of a seed with high water content is negative enough to cause water to move from a moist environment into the seed. Many conifer seed have the capacity to withstand several wetting–drying cycles with-out losing germination capacity—even after chilling to break dormancy. The changes in seed constituents that stem from enzyme activity have been most thoroughly documented for Pseudotsuga menziesii by T. M. Ching. Other conifers have a similar pattern of mobilization and use.
