Seeds

Abstract

In the seed‐bearing plants (angiosperms and gymnosperms), the embryo‐containing seed develops from the fertilised ovule. Other tissues might also be present in the mature seed such as the endosperm (angiosperms) and the megagametophytic tissue in gymnosperms. During its formation, storage reserves are deposited in various parts of the seed. The structural and physiological features that develop during transition of the ovule into a seed confer upon it properties that account for its greatly successful role in the life cycle of the dominant plants on earth. These include the reserves, the various dispersal mechanisms and in the majority of species, the ability to withstand desiccation, which is connected with the longevity of seeds in the ‘dry’ state. Seed dormancy, where present, serves later to determine the place and time of germination. Regulation of seed processes is achieved by control of gene expression, including by the hormones abscisic acid and gibberellin. Seeds were critically important in plant domestication and are currently important in plant biotechnology.

Key Concepts:

  • A seed develops from a fertilised ovule and consists of an embryo and other tissues of different developmental origins.

  • The seed occupies a key position in the life cycle of higher plants and accounts for the great success of angiosperms and gymnosperms.

  • During its development, the seed lays down relatively high proportions of storage reserves for the later support of early seedling growth.

  • In most species, seeds tolerate the desiccation that terminates their development and thereafter remain alive for long durations in a quiescent state.

  • Seeds develop various structural features that later aid their dispersal.

  • During development, seeds of many species become dormant, a condition that later blocks germination until after certain environmental signals have been experienced.

  • Regulation of gene expression by hormones and other factors is central to the various processes that occur in seeds.

  • Various features of seeds had a key role in plant domestication and the development of crop species.

  • Seeds are central to plant biotechnology and the design of new crop types.

Keywords: seed; structure; development; desiccation; domestication; dormancy and germination; success; biotechnology

Figure 1.

Structure of different seeds as shown in longitudinal section (from various sources).

Figure 2.

Events in seed development. Gene expression and other events during the time course of seed development are indicated. Top row: Embryogenesis (the example chosen is Arabidopsis, but the major developmental changes are typical of a dicotyledonous seed). The time course is indicated by the large red arrow. A, apical cell; B, basal cell; Ax, embryo axis; C, cotyledon(s); E, embryo; En, endosperm and S, suspensor. Genes: The following have been identified from studies on many mutants of Arabidopsis: (1) GNOM regulates the position of the first zygotic division. In the mutant, this division is symmetrical; (2) MONOPTEROS regulates cell divisions in the very early (pro) embryo. In the mutant, there are 16 cells in what is normally the 8‐cell stage. The development of the basal part of the embryo (giving the axis) is abnormal; (3) FACKEL regulates differentiation in the central zone of the globular‐stage embryo. In the mutant, the hypocotyl fails to develop; (4) GURKE regulates development in the apical region. The mutant has no apical meristem and the cotyledon primordia do not form. Many others have been described.

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References

Angelovici R, Galili G, Fernie AR and Fait A (2010) Seed desiccation: a bridge between maturation and germination. Trends in Plant Science 15: 211–218.

Buitink J and Leprince O (2008) Intracellular glasses and seed survival in the dry state (États vitreux intracellulaires et survie des graines à l’état sec). Comptes Rendus Biologies 331: 788–795.

Kesseler R and Stuppy W (2006) Seeds: Time capsules of life. London: Papadakis Publishers.

Linkies A, Graeber K, Knight C and Leubner‐Metzger G (2010) The evolution of seeds. New Phytologist 186: 817–831.

Nonogaki H, Bassel GW and Bewley JD (2010) Germination – still a mystery. Plant Science 179: 574–581.

Further Reading

Baskin CC and Baskin JM (1998) Seeds: Ecology, Biogeography, and Evolution of Dormancy and Germination. San Diego, CA: Academic Press.

Bewley JD and Black M (1994) Seeds: Physiology of Development and Germination, 2nd edn. New York: Plenum Press.

Black M, Bewley JD and Halmer P (eds) (2008) The Encyclopedia of Seeds: Science, Technology and Uses. Wallingford: CABI.

Bradford K and Nonogaki H (eds) (2007) Seed Development, Dormancy and Germination. Oxford: Blackwell Publishing Ltd.

Kigel J and Galili G (eds) (1995) Seed Development and Germination. New York: Marcel Dekker.

Larkins BA and Vasil IK (eds) (1997) Cellular and Molecular Biology of Plant Seed Development. Dordrecht: Kluwer Academic.

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How to Cite close
Black, Michael(Mar 2011) Seeds. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0002043.pub2]