Seed Development and Germination

Authors: CHEN, FENG - University Of Tennessee; Martin, Ruth; SONG, SONGQUAN - Chinese Academy Of Sciences; NONOGAKI, HIROYUKI - Oregon State University

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 6/15/2009
Publication Date: 11/19/2010
Citation: Chen, F., Martin, R.C., Song, S., Nonogaki, H. 2010. Seed Development and Germination. In: Trigiano, R.N. and Gray, D.J. Plant Tissue Culture, Development and Biotechnology. Boca Raton: CRC Press. 9:127-140.

Interpretive Summary: This book chapter describes the role of the embryo, endosperm and testa during seed formation – where they develop from and what they will become in the mature plant. The various stages of embryogenesis, which involve cell division and differentiation, and the processes occurring within each stage, are described. Variation in endosperm development and the accumulation of major seed reserves, carbohydrates, oils and proteins, in different species is discussed. The process of “maturation drying” a time during which the sugar and oligosaccharide content of the seed increases and the water content decreases is discussed. Seeds become desiccation tolerant during this time and the metabolism of the seed is greatly reduced. Seed germination is defined as the resumption of growth of the embryonic plant within the mature seed. Water uptake by the seed, which plays and important role in seed germination, is discussed in this chapter. The physical constraints of the endosperm and the testa to embryo growth must be overcome by the embryo growth potential in order for radicle protrusion or germination to occur. Some seeds will not germinate, even under optimal conditions and these seeds are “dormant”. The types of seed dormancy, classified as morphological, physiological or morphophysiological, physical or combinational dormancy, are discussed. The regulation of germination by hormones and environmental factors is also presented.

Technical Abstract: Seed is the fertilized and matured ovule of angiosperms and gymnosperms and represents a crucial stage in the life cycle of plants. Seeds of diverse plant species may display differences in size, shape and color. Despite apparent morphological variations, most mature seeds consist of three major components: the embryo, the endosperm and the testa (seed coat) (Figure 1). The embryo consists of leaf, stem and root precursor tissues. Growth of the embryo out of the seed leads to the formation of a seedling. The endosperm is the tissue that surrounds the embryo and provides nourishment for the development and growth of embryo and seedling. In some seeds, the endosperm is reduced to a few cell layers or may completely disappear at maturity. In these seeds, food reserves are stored in cotyledons. The testa surrounds the embryo and endosperm and provides a protective covering for the seed. Seeds have a number of unique properties. Most seeds are highly tolerant to desiccation. Compared to the vegetative portions of plants which are sessile, seeds are relatively mobile. They can be dispersed by animals, wind or water. Additionally, seed germination is regulated by many internal and external factors, which usually optimize the distribution of germination over time in a population of seeds. These properties contribute significantly to the success of seed plants on earth. In addition to their role in plant reproduction, seeds are a vital component of the human diet. The majority of the world’s food staple consists of seeds (e.g., cereal grains). Because of the importance of seeds as food and a genetic delivery system, seed biology has been an important area of both basic and applied plant science. In this chapter, we will describe the biological and physiological events that occur during seed development and germination as well as the dormancy mechanisms that regulate the germination process.