12 Seed Dormancy and Germination

Abstract

Seeds are designed to permit the mature embryo, surrounded by its seed coat, to survive the period between detachment from the parental plant and its establishment as a new seedling. Seeds have a number of characteristics related to their survival strategy. They are resistant to desiccation; they possess food reserves, assumed to be required for proper growth as a seedling; and they exhibit seed dormancy, a mechanism that prevents germination in periods unfavorable for seedling growth but allows germination at the proper time in the right environment. A well-adapted species only germinates at the beginning of the season that benefits seedling growth, which allows the completion of the life cycle. Thus, proper timing of germination is essential for survival of the species.

Arabidopsis is an annual distributed over a large part of the northern, mainly temperate, parts of the world. Since in many sites it flowers before the onset of a warm and dry summer, it can survive that summer period only in the seed stage. In general, conditions become favorable for germination during the fall when seeds germinate, and then the plants survive winter as seedlings or young nonflowering plants (Baskin and Baskin 1972). This is the typical behavior of a winter annual. In some cases, seed germination is postponed until the following spring, where-after the plant completes its life cycle in the same year (Ratcliffe 1976). Arabidopsis is well suited for the study of the physiological mechanisms of dormancy and germination, because as a “wild” plant, it still...