Chapter 4 - Germination Ecology of Seeds with Nondeep Physiological Dormancy

Abstract

The chapter illustrates the changes in dormancy states of seed with nondeep physiological dormancy. It also discusses how these changes in dormancy states are affected by various environmental factors. Emphasis is placed on how changes in germination responses of the seeds interact with the environment to control the timing of seed germination in the field. However, data from studies in which soil is plowed, or disturbed at regular intervals throughout the year, shows that seeds of many species germinate only at specific times of the year. Moreover, some species whose seeds have nondeep physiological dormancy (PD) at maturity, cycle back and forth between dormancy and nondormancy many times before they eventually germinate. The change from dormancy to nondormancy, or from non-dormancy to dormancy, is gradual and it occurs in response to changes in environmental factors. Thus, during the course of a year, seeds that go from dormancy to nondormancy and then back to dormancy, thereby exhibit an annual cycle. Seeds with nondeep PD are the only ones that can reenter dormancy and thus, exhibit annual cycles in their dormancy states.