Chapter 19 - Seed Germination, Mobilization of Food Reserves, and Seed Dormancy

Abstract

. Seed dormancy is a phenomenon of considerable importance in the survival of plants. Abscisic acid (ABA) present in sufficient concentration at certain stages in seed development, is the inducing factor for seed dormancy, but the depth of dormancy induction depends on the genetic makeup of the plant and on environmental factors, such as prevailing temperature, relative humidity, and day length. The variety of factors that influence seed dormancy makes it a highly complex phenomenon to study. However, the resultant variability in the dormancy of seeds of a species is extremely beneficial to its survival because it enables the seeds in the seed bank to stagger their germination in the field. Primary dormancy, which is induced during seed development, is of several types. Coat-related dormancy is due to the tissues that surround the embryo acting as a mechanical or permeability barrier. Embryo-related dormancy resides in the embryo itself and, for breakage, requires warm, dry storage, chilling, or perception of red light via a phytochrome. Gibberellins are involved in embryo-related dormancy because in many cases, seeds, which require afterripening or chilling, germinate if supplied with gibberellic acids (GAs) in the absence of those treatments.