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Journal ArticleDOI

Seed dormancy and the control of germination

01 Aug 2006-New Phytologist (Wiley/Blackwell (10.1111))-Vol. 171, Iss: 3, pp 501-523
TL;DR: It is argued that adaptation has taken place on a theme rather than via fundamentally different paths and similarities underlying the extensive diversity in the dormancy response to the environment that controls germination are identified.
Abstract: Seed dormancy is an innate seed property that defines the environmental conditions in which the seed is able to germinate. It is determined by genetics with a substantial environmental influence which is mediated, at least in part, by the plant hormones abscisic acid and gibberellins. Not only is the dormancy status influenced by the seed maturation environment, it is also continuously changing with time following shedding in a manner determined by the ambient environment. As dormancy is present throughout the higher plants in all major climatic regions, adaptation has resulted in divergent responses to the environment. Through this adaptation, germination is timed to avoid unfavourable weather for subsequent plant establishment and reproductive growth. In this review, we present an integrated view of the evolution, molecular genetics, physiology, biochemistry, ecology and modelling of seed dormancy mechanisms and their control of germination. We argue that adaptation has taken place on a theme rather than via fundamentally different paths and identify similarities underlying the extensive diversity in the dormancy response to the environment that controls germination.

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Citations
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Journal ArticleDOI
TL;DR: The net result is a slightly heterogeneous response, thereby providing more temporal options for successful germination.
Abstract: Seed dormancy provides a mechanism for plants to delay germina- tion until conditions are optimal for survival of the next generation. Dormancy release is regulated by a combination of environmental and endogenous signals with both synergistic and competing effects. Molecular studies of dormancy have correlated changes in transcrip- tomes, proteomes, and hormone levels with dormancy states ranging from deep primary or secondary dormancy to varying degrees of re- lease. The balance of abscisic acid (ABA):gibberellin (GA) levels and sensitivity is a major, but not the sole, regulator of dormancy status. ABA promotes dormancy induction and maintenance, whereas GA promotes progression from release through germination; environ- mental signals regulate this balance by modifying the expression of biosynthetic and catabolic enzymes. Mediators of environmental and hormonal response include both positive and negative regulators, many of which are feedback-regulated to enhance or attenuate the response. The net result is a slightly heterogeneous response, thereby providing more temporal options for successful germination.

1,153 citations


Cites background from "Seed dormancy and the control of ge..."

  • ...Genetic studies have shown that ABA produced by maternal tissues or supplied exogenously is not sufficient to induce dormancy (50, 51), implying that this is a form of embryo-controlled dormancy dependent on ABA synthesis in the embryo and/or endosperm....

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  • ...Seed dormancy has been described as “one of the least understood phenomena in seed biology” (50) and remains confusing despite much recent progress....

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  • ...Further evidence suggesting the importance of ABI-like genes in dormancy regulation comes from studies of their orthologs in other dicots, cereals, and even conifers (50, 97)....

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Journal ArticleDOI
TL;DR: Current knowledge of the molecular control of this trait in Arabidopsis thaliana is presented, focussing on important components functioning during the developmental phases of seed maturation, after-ripening and imbibition.
Abstract: The transition between dormancy and germination represents a critical stage in the life cycle of higher plants and is an important ecological and commercial trait. In this review we present current knowledge of the molecular control of this trait in Arabidopsis thaliana, focussing on important components functioning during the developmental phases of seed maturation, after-ripening and imbibition. Establishment of dormancy during seed maturation is regulated by networks of transcription factors with overlapping and discrete functions. Following desiccation, after-ripening determines germination potential and, surprisingly, recent observations suggest that transcriptional and post-transcriptional processes occur in the dry seed. The single-cell endosperm layer that surrounds the embryo plays a crucial role in the maintenance of dormancy, and transcriptomics approaches are beginning to uncover endosperm-specific genes and processes. Molecular genetic approaches have provided many new components of hormone signalling pathways, but also indicate the importance of hormone-independent pathways and of natural variation in key regulatory loci. The influence of environmental signals (particularly light) following after-ripening, and the effect of moist chilling (stratification) are increasingly being understood at the molecular level. Combined postgenomics, physiology and molecular genetics approaches are beginning to provide an unparalleled understanding of the molecular processes underlying dormancy and germination.

831 citations


Cites background from "Seed dormancy and the control of ge..."

  • ...In Arabidopsis the embryo is surrounded by the single-cell endosperm (also called aleurone) layer, which is also the result of double fertilization (Finch-Savage & Leubner-Metzger, 2006), and the testa (Debeaujon et al., 2000) (Fig....

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  • ...Once this window is passed, the requirement for RGL2 destruction no longer exists, highlighting the functionality of after-ripening as a process of changing ‘windows’ of sensitivity to external and internal signals (Finch-Savage & Leubner-Metzger, 2006)....

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  • ...Germination is defined as the emergence of the radicle through surrounding structures (Bewley, 1997b; Baskin & Baskin, 2004; Finch-Savage & Leubner-Metzger, 2006)....

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  • ...The definition of seed dormancy has been reviewed by Finch-Savage & Leubner-Metzger (2006) and is generally given as the incapacity of a viable seed to germinate under favourable conditions....

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  • ...The role of ABA signalling and biosynthesis in germination completion The role of ABA has classically been defined as that of a repressor of germination completion (Finch-Savage & Leubner-Metzger, 2006)....

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Journal ArticleDOI
TL;DR: The concept of the "oxidative window for germination" as mentioned in this paper restricts the occurrence of the cellular events associated with germination to a critical range of reactive oxygen species (ROS) level, enclosed by lower and higher limits.

658 citations

Journal ArticleDOI
TL;DR: Evidence is reviewed which indicates that Ca2+ channel, Ca2-ATPase andCa2+ exchanger isoforms can indeed modulate specific Ca2+.
Abstract: In numerous plant signal transduction pathways, Ca2+ is a versatile second messenger which controls the activation of many downstream actions in response to various stimuli. There is strong evidence to indicate that information encoded within these stimulus-induced Ca2+ oscillations can provide signalling specificity. Such Ca2+ signals, or 'Ca2+ signatures', are generated in the cytosol, and in noncytosolic locations including the nucleus and chloroplast, through the coordinated action of Ca2+ influx and efflux pathways. An increased understanding of the functions and regulation of these various Ca2+ transporters has improved our appreciation of the role these transporters play in specifically shaping the Ca2+ signatures. Here we review the evidence which indicates that Ca2+ channel, Ca2+-ATPase and Ca2+ exchanger isoforms can indeed modulate specific Ca2+ signatures in response to an individual signal.

620 citations

Journal ArticleDOI
TL;DR: An integrated view on the early phase of seed germination is provided and it is shown that it is characterized by dynamic biomechanical changes together with very early alterations in transcript, protein, and hormone levels that set the stage for the later events.
Abstract: Most plant seeds are dispersed in a dry, mature state. If these seeds are non-dormant and the environmental conditions are favourable, they will pass through the complex process of germination. In this review, recent progress made with state-of-the-art techniques including genome-wide gene expression analyses that provided deeper insight into the early phase of seed germination, which includes imbibition and the subsequent plateau phase of water uptake in which metabolism is reactivated, is summarized. The physiological state of a seed is determined, at least in part, by the stored mRNAs that are translated upon imbibition. Very early upon imbibition massive transcriptome changes occur, which are regulated by ambient temperature, light conditions, and plant hormones. The hormones abscisic acid and gibberellins play a major role in regulating early seed germination. The early germination phase of Arabidopsis thaliana culminates in testa rupture, which is followed by the late germination phase and endosperm rupture. An integrated view on the early phase of seed germination is provided and it is shown that it is characterized by dynamic biomechanical changes together with very early alterations in transcript, protein, and hormone levels that set the stage for the later events. Early seed germination thereby contributes to seed and seedling performance important for plant establishment in the natural and agricultural ecosystem.

615 citations

References
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Book
10 Jun 1998
TL;DR: A Geographical Perspective on Germination Ecology: Tropical and Sub-tropical Zones as discussed by the authors, Temperate and Arctic Zones, and Semi-Arctic Zones: Temperate, Subtropical, and Arctic zones.
Abstract: Introduction. Ecologically Meaningful Germination Studies. Types of Seed Dormancy. Germination Ecology of Seeds with Nondeep Physiological Dormancy. Germination Ecology of Seeds with Morphophysiological Dormancy. Germination Ecology of Seeds with Physical Dormancy. Germination Ecology of Seeds in the Persistent Seed Bank. Causes of Within-Species Variations in Seed Dormancy and Germination Characteristics. A Geographical Perspective on Germination Ecology: Tropical and Subtropical Zones. A Geographical Perspective on Germination Ecology: Temperate and Arctic Zones. Germination Ecology of Plants with Specialized Life Cycles and/or Habitats. Biogeographical and Evolutionary Aspects of Seed Dormancy. Subject Index.

4,307 citations

Book
31 Jul 1994
TL;DR: Seeds: Germination, Structure, and Composition; Development-Regulation and Maturation; Mobilization of Stored Seed Reserves; and some Ecophysiological Aspects.
Abstract: Seeds: Germination, Structure, and Composition. Seed Development and Maturation. Development-Regulation and Maturation. Cellular Events during Germination and Seedling Growth. Dormancy and the Control of Germination. Some Ecophysiological Aspects of Germination. Mobilization of Stored Seed Reserves. Control of the Mobilization of Stored Reserves. Seeds and Germination: Some Agricultural and Industrial Aspects. Index.

3,492 citations


"Seed dormancy and the control of ge..." refers background in this paper

  • ...Journal compilation © New Phytologist (2006) Review504 light changes the seed so that it can germinate in darkness and is therefore the last step in the dormancy-breaking process, rather than the first step in the germination process (Bewley & Black, 1994; Pons, 2000; Leubner-Metzger, 2003)....

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  • ...…both dormancy and germination and that light regulates germination; however, it is a matter of debate whether light is also a regulator of dormancy (Bewley & Black, 1994; Vleeshouwers et al ., 1995; Casal & Sanchez, 1998; Pons, 2000; Baskin & Baskin, 2004; Fenner & Thompson, 2005; Kucera et al .,…...

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Journal ArticleDOI
TL;DR: This review provides both an overview of the essential processes that are associated with germination and a description of the possible impediments thereto that may result in dormancy.
Abstract: Seeds are a vital component of the world’s diet. Cereal grains alone, which comprise -90% of all cultivated seeds, contribute up to half of the global per capita energy intake. Not surprisingly then, seed biology is one of the most extensively researched areas in plant physiology. Even in relation to the topics reviewed here, a casual perusal of the Agricola database reveals that well over 5000 publications on seed germination and 700 on seed dormancy have appeared in the last decade. Yet we still cannot answer two fundamental questions: how does the embryo emerge from the seed to complete germination, and how is embryo emergence blocked so that seeds can be maintained in the dormant state? Obviously, with such a large literature on the subject, this review is far from comprehensive. Nevertheless, it provides both an overview of the essential processes that are associated with germination and a description of the possible impediments thereto that may result in dormancy. With the seed, the independence of the next generation of plants begins. The seed, containing the embryo as the new plant in miniature, is structurally and physiologically equipped for its role as a dispersa1 unit and is well provided with food reserves to sustain the growing seedling until it establishes itself as a self-sufficient, autotrophic organism. Because the function of a seed is to establish a new plant, it may seem peculiar that dormancy, an intrinsic block to germination, exists. But it may not be advantageous for a seed to germinate freely, even in seemingly favorable conditions. For example, germination of annuals in the spring allows time for vegetative growth and the subsequent production of offspring, whereas germination in similar conditions in the fall could lead to the demise of the vegetative plant during the winter. Thus, dormancy is an adaptive trait that optimizes the distribution of germination over time in a population of seeds. Seed dormancy is generally an undesirable characteristic in agricultural crops, where rapid germination and growth are required. However, some degree of dormancy is advantageous, at least during seed development. This is particularly true for cereal crops because it prevents germination of grains while still on the ear of the parent plant (preharvest sprouting), a phenomenon that results in major losses to the

2,545 citations


"Seed dormancy and the control of ge..." refers background or methods in this paper

  • ...Cell elongation is necessary and is generally accepted to be sufficient for the completion of radicle protrusion (visible germination) (Bewley, 1997a; Kucera et al ., 2005)....

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  • ...…Introduction Seed dormancy could be considered simply as a block to the completion of germination of an intact viable seed under favourable conditions, but earlier reviews concluded that it is one of the least understood phenomena in the field of seed biology (Hilhorst, 1995; Bewley, 1997a)....

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  • ...…and promotion of germination After-ripening, i.e. a period of usually several months of dry storage at room temperature of freshly harvested, mature seeds, is a common method used to release dormancy (Bewley, 1997a; Probert, 2000; Leubner-Metzger, 2003; Kucera et al., 2005; Bair et al., 2006)....

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  • ...…in this mechanical resistance of the micropylar endosperm (the endosperm layer covering the radicle tip) appears to be a prerequisite for radicle protrusion during seed germination (for reviews, see Hilhorst, 1995; Bewley, 1997b; Leubner-Metzger, 2003; Sanchez & Mella, 2004; Kucera et al., 2005)....

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  • ...These studies show that the intrinsic molecular mechanisms determining dormancy can have an embryo and/or a coat component (Hilhorst, 1995; Bewley, 1997a; Kucera et al., 2005)....

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