e-book

Seed Development, Dormancy and Germination

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The formation, dispersal, and germination of seeds are crucial stages in the life
cycles of gymnosperm and angiosperm plants. The unique properties of seeds, particularly
their tolerance to desiccation, their mobility, and their ability to schedule
their germination to coincide with times when environmental conditions are favorable
to their survival as seedlings, have no doubt contributed significantly to
the success of seed-bearing plants. Humans are also dependent upon seeds, which
constitute the majority of the world’s staple foods (e.g., cereals and legumes), and
those crops are also dependent upon seeds as propagules for establishing new fields
each year. Seeds are an excellent system for studying fundamental developmental
processes in plant biology, as they develop from a single fertilized zygote into an
embryo and endosperm in association with the surrounding maternal tissues. As
genetic and molecular approaches have become increasingly powerful tools for biological
research, seeds have become an attractive system in which to study a wide
array of metabolic processes and regulatory systems. The rapid pace of discovery,
particularly in the model system Arabidopsis thaliana, and the complexity of the
molecular interactions being uncovered provided the rationale for a book by leading
experts to update our state of knowledge concerning seed development, dormancy,
and germination.

This volume focuses on specific aspects of seed biology associated with the role
of seeds as propagules. Thus, important processes in seeds, such as the accumulation
of storage reserves and their subsequent mobilization during germination, are not
covered in depth here. Instead, the emphasis in the development section (Chapters 1
and 2) is on the processes that contribute to seed growth and to the induction of
dormancy during maturation, rather than on the very early steps of embryogenesis,
which are covered in a number of other books and reviews. Dormancy is a rather
mysterious physiological state in which imbibed seeds are metabolically active,
yet do not progress into germination and growth. As developmental arrest is a
widespread phenomenon in biology, insight into seed dormancy will have broad
implications. Chapter 3 discusses the types of dormancy exhibited by seeds and the
current hypotheses concerning the mechanisms by which environmental signals are
transduced into regulatory mechanisms controlling dormancy. This is followed in
Chapter 4 by a discussion and examples of approaches to modeling seed dormancy
and germination in an ecological context. Such models have practical utility for
vegetation management in both agricultural and wildland contexts, and they also
identify and quantify response mechanisms for physiological investigation.

While details are still sketchy, the genetic basis of seed dormancy is being
elucidated in several systems, including Arabidopsis, rice (Oryza sativa), and other
cereals. Chapter 5 provides an overview and update on the genetic regulation of seed
dormancy. Genes and mutations affecting dormancy and germination have identified
a number of regulatory pathways, particularly those involving gibberellins (GA)
and abscisic acid (ABA), that appear to be crucial for the development, maintenance,
and loss of dormancy. Metabolic pathways are also involved, with lipid metabolism
in particular playing an important role, as described in Chapter 6.Arole for metabolic
and respiratory pathways in regulating germination has been known for several
decades, but new insights from work on nitric oxide discussed in Chapter 7 provide
an integrating hypothesis for reinterpreting those earlier insights.

While GA and ABA are central players in regulating seed dormancy and germination,
other plant hormones, including ethylene, auxin, cytokinins, and brassinosteroids,
play important supporting roles. The complexity of these interacting
hormonal signaling networks associated with seed dormancy is discussed in Chapter
8. Feedback loops involving hormonal synthesis, catabolism, and sensitivity
govern diverse aspects of seed dormancy and initiation of germination. The specific
genes encoding key enzymes in these hormonal synthesis and catabolism pathways
are summarized in Chapter 9. The proteins involved in the signaling pathways
through which these hormones act are also being uncovered. Chapter 10 reviews
the important role of protein degradation pathways in controlling the transcription
of germination-related genes. Once dormancy has been released and germination
has been triggered, additional genes and mechanisms are involved in the growth of
the embryo and its protrusion through any enclosing tissues – processes that are reviewed
in Chapter 11. A final checkpoint appears to occur shortly after germination
in the transition to seedling growth. Seeds are particularly sensitive to the effects of
sugars at this stage, as described in Chapter 12.

Our goal in developing the book was to give a comprehensive look at seed
biology from the point of view of the developmental and regulatory processes that
are involved in the transition from a developing seed through dormancy and into
germination and seedling growth. We wished to illustrate the complexity of the
environmental, physiological, molecular, and genetic interactions that occur through
the life cycle of seeds along with the concepts and approaches used to analyze
seed dormancy and germination behavior. It has been over 10 years since a book
devoted specifically to this topic has been published, and the progress made in that
period is remarkable. The utility of Arabidopsis as a model system is evident in the
focus of a number of chapters on work in this species. In addition, other chapters
describe the broader implications and applications in ecological contexts of insights
gained from model systems. This book provides plant developmental biologists,
geneticists, plant breeders, seed biologists, graduate students, and teachers a current
review of the state of knowledge on seed development, dormancy, and germination
and identifies the current challenges and remaining questions for future research.
The book will have been a success if it contributes to stimulating a new increment
of seed biology research in the next 10 years to match or exceed that of the past
decade.

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Ketersediaan

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Informasi Detail

Judul Seri

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No. Panggil

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Penerbit

Oxford : Blackwell Publishing Ltd., 2007

Deskripsi Fisik

QK661.S415 - 581.467–dc22

Bahasa

English

ISBN/ISSN

978-1-4051-3983-0

Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

PERTANIAN.
BIOLOGI
FISIOLOGI TUMBUHAN

Info Detail Spesifik

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Pernyataan Tanggungjawab

agus

Versi lain/terkait

Lampiran Berkas

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