Table Of ContentRecent Advances in the
Development and
Germination of Seeds
NATO ASI Series
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Volume 187-Recent Advances in the Development and Germination of Seeds
edited by Raymond B. Taylorson
Series A: Life Sciences
Recent Advances in the
Development and
Germination of Seeds
Edited by
Raymond B. Taylorson
United States Department of Agriculture
Beltsville, Maryland
Plenum Press
New York and London
Published in cooperation with NATO Scientific Affairs Division
Proceedings of the Third International Workshop on Seeds,
sponsored by NATO,
held August 6-12, 1989,
in Williamsburg, Virginia
Library of Congress Cataloging-In-Publication Data
International Workshop on Seeds (ard , 1999 , Williamsburg. Va.)
Rscent advances in the developMent and germination of seeds I
edited by Ray.ond B. Taylorson.
p. eM. -- (NATO ASI series. Series A. Life sciences; vol.
1971
"Proceedings of the Third International Workshop on Seeds.
sponsored by NATO. held August 6-12. 1989. in Wi Ili8llsburg.
Virginia"--T.p. verso.
Includes bibliographical references.
ISBN-13: 978-1-4612-7894-8 a-ISBN-13: 978-1-4613-0617-7
DOI:l0.l007/978-1-4613-0617-7
1. Seeds--Development--Congresses. 2. Gerlinatlon--Congresses.
I. Taylorson. RaYlond B. II. North Atlantic Treaty Organization.
III. Title. IV. Series, NATO ASI series. Series A. Life sciences
v. 187.
QK661. 156 1989
582' .0467--dc20 90-33668
CIP
© 1989 Plenum Press, New York
Softcover reprint of the hardcover 1s t edition 1989
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All rights reserved
No part of this book may be reproduced, stored in a retrieval system, or transmitted
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PREFACE
These Proceedings are a product of the International
Workshop on Seeds held in Williamsburg, Virginia, USA, at the
College of William and Mary, during the week of August 6-11,
1989. Sixty-eight participants attended. The location
provided a scenic and historical setting for the excellent work
presented. Good facilities and amenities also contributed to
the success of the meeting.
The Proceedings present the substance of the main lectures
given at this meeting. In addition, there were 29 brief paper
presentations and 30 poster presentations which have been
summarized in abstract form in a separate publication.
This meeting represents the third such meeting of a diverse
group of scientists interested in the behavior of seeds, both
in an agricultural sense and as tools for the advancement of
more particular matter. The first meeting was held in
s~bject
Jerusalem, Israel in 1980 and the second in Wageningen, The
Netherlands in 1985. A fourth meeting is being planned.
The Editor and Organizer wishes to thank not only the
contributors to this volume for their efforts but also all the
other participants whose combined efforts made this meeting a
great success.
R. B. Taylorson
Beltsville, Maryland
v
CONTENTS
Seed Research-Past,Present and Future .... ..... ... .... 1
M. Black
Use of Transgenic Plants for Studies of
Seed-Specific Gene Expression.. .......... ..... 7
P.A. Lessard, R.D. Allen, F. Bernier and
R.N. Beachy
Impact of Simulated Drought stress on Protein Body
Cycle in Radicles of Developing and
Germinating Cotton Seeds ...................... 19
E.L. Vigil
Synthetic seed for Clonal Production of Crop
Plants ........................................ 29
D.J. Gray
Synthesis of Acid-Soluble,ABA-Inducible Proteins
in Wheat Embryos from Dormant Grain ........... 47
M. Walker-Simmons, R.E. Crane and S. Yao
Hormones, Genetic Mutants and Seed Development .. ..... 57
J.D. Smith, F. Fong, C. W. Magill, B.G. Cobb
and D.G.Bai
Membrane Behavior in Drought and Its Physiological
Significance .................................. 71
F.A. Hoekstra, J.H. Crowe and L.M. Crowe
The Basis of Recalcitrant Seed Behaviour: Cell
Biology of the Homoiohydrous Seed Condition 89
P. Berjak, J.M. Farrant and N.W. Pammenter
Phytin Synthesis and Deposition 109
J.S. Greenwood
Calcium-Regulated Metabolism in Seed Germination ..... 127
S.J. Roux
Transport and Targeting of Proteins to Protein
Storage Vacuoles (Protein Bodies) in
Developing Seeds 139
M.J. Chrispeels and B.W. Tague
Biochemical Adaptations to Anoxia in Rice and
Echinochloa Seeds ............................. 151
R.A. Kennedy, T.C. Fox, L.D. Dybiec and
M.E. Rumpho
Some Aspects of Metabolic Regulation of Seed
Germination and Dormancy... ................... 165
D. Come and F. Corbineau
Phytochrome and Sensitization in Germination
Control ....................................... 181
W. VanDerWoude
The Role of Light and Nitrate in Seed Germination .... 191
H.W.M. Hilhorst and C.M. Karssen
Water-Impermeable Seed Coverings as Barriers to
Germination ................................... 207
G.H. Egley
Control of Germination and Early Development in
Parasitic Angiosperms .......... .......... ..... 225
M.P. Timko, C.S. Florea and J.L. Riopel
Factors Eliciting the Germination of Photoblastic
Kalanchoe Seeds ............................... 241
J.A. De Greef,H. Fredericq, R. Rethy, A.
Dedonder, E. De Petter and L. Van Wiemeersch
Factors Influencing the Efficacy of Dormancy-
Breaking Chemicals ............................ 261
M.A. Cohn
Physiological Mechanisms Involved in Seed Priming 269
C.M. Karssen, A. Haigh, P. van der Toorn and
R. Weges
Germination Research Towards the Nineties: A
Summary and Prognosis ......................... 281
A. M. Mayer
Index ................................................ 289
viii
SEED RESEARCH -PAST. PRESENT AND FUTURE
Michael Black
Division of Biosphere Sciences
King's College (University of London)
Campden Hill Road
London W8 7 AH. England
THE PAST LEADING TO THE PRESENT
Research on seeds has a long history. Most botanists know about the
writings of the Greek scholar Theophrastus (372-287 BC). He displayed an
awareness of seed physiology that would not disgrace the pages of books
written two millenia after his death. Dormancy. reserve deposition. the
effects of environmental factors on seed development and germination. seed
longevity and priming - topics which are in the forefront of modern
research - all received his comments (see Evenari. 1984). Relatively little
new knowledge was added until the end of the 18th century: and from the
late 19th and early 20th century studies on seeds grew apace to meet the
demands of agriculture. horticulture. forestry. malting and brewing and as
part of the search for an understanding as to how the physical and biological
worlds function.
Seeds have been the objects of many different kinds of research. As
they are quantitatively the most important parts of the human diet (cereals.
pulses. etc.) nutritionists demanded detailed knowledge of their chemical
composition. Applied chemistry (phytochemistry. cereal chemistry)
provided information about the starch. protein and fat reserves, which later
became the immensely valuable starting point for studies by plant
biochemists and molecular biologists on the biochemical and molecular
mechanisms involved in reserve deposition.
Most of our important economic crop plants (food plants. forest trees)
are grown from seeds and so from a purely practical view it has been
necessary to learn about their germination physiology. This includes how
germination is affected by physical and chemical factors in the seed's
environment - temperature. water. light. inhibitors. etc. - and also how it is
regulated by factors within the seed itself. i.e. its dormancy. These
considerations are of course important to the ecologist as they can tell him
about the processes involved in plant establishment. And the success of
seeds also rests on their viability. and on their quick and uniform
development into healthy. well-growing seedlings. i.e. their vigour. Both of
these depend substantially upon conditions experienced by the seeds in
storage (or in nature. in the seed banle:) and so much research has been
carried out on the relationship between factors such as temperature and
humidity. seed moisture content. and viability and longevity.
Recent Advances in the Development and Germination of Seeds
Edited by R.B. Taylorson
Plenum Press, New York
As seedling establishment involves the mobilisation of the seeds'
storage reserves the processes occurring here have attracted the seed
researcher's attention. In an economic context one aspect of mobilisation
has received particularly intensive study the modification of the
endosperm in the first few days following germination of barley, i.e.
malting. And to this time it is the mobilisation in the cereal grain which of
all seed types is best understood. Arising out of this is an example of how
seed research has contributed to fundamental knowledge about plant
processes. The observations made early in the 20th century concerning
embryo/endosperm interactions in malting barley eventually became
explicable in terms of action of a hormone secreted by the embryo,
gibberellin, upon the aleurone tissue surrounding the starchy endosperm.
This is still the best understood hormone/target tissue system in plants. one
which has contributed enormously to our understanding of the biochemistry
and molecular biology of hormone action and the regulation of gene
expression (Jacobsen and Chandler. 1987). It is worth mentioning in this
context that the plant hormones themselves were discovered as a result of
research on seeds. Auxins. gibberellins and cytokinins were first isolated
from seed tissues of higher plants; and seeds are also known as rich sources
of abscisic acid and ethylene.
Much fundamental research on plant biochemistry has been carried
out with seeds. mostly in respect of metabolic processes concerned with
reserve synthesis and utilisation. Hence, much of our knowledge about the
synthesis and breakdown of fatty acids. triacylglycerols and starch. and
about protein processing comes from studies on seeds. Sub-cellular events
involved in reserve metabolism - protein packaging. secretion. spherosome,
glyoxysome. peroxisome and lysosome functions - have been elucidated using
seed and seedling material.
One of the greatest contributions that seed research has made to
botanical science is undoubtedly concerned with the discovery of
phytochrome, the pigment involved in a myriad of light-controlled
developmental processes occurring at all phases in the plant's life history.
As every botanist knows, the first steps on the road to the discovery of
phytochrome. in lettuce seeds, were taken in Beltsville. not many miles from
the site of this meeting. by Flint and McAlister, culminating in the
momentous research of Borthwick. Hendricks. the Tooles and their
colleagues (Borthwick. 1972). Seed researchers can justly be proud of the
contributions that their system continued to make to plant photophysiology.
for example in the discovery of the high energy reaction.
As mentioned above. seeds have been a focus of attention of ecologists.
Individual plant and community establishment depend on seed dispersal, and
all facets of seed physiology play a part thereafter. The relationship
between the seed and its environment is an important determinant of the
quality and quantity of the seed bank, and the eventual emergence of
seedlings depends upon longevity, germination physiology, dormancy and
effective reserve utilisation. The conservationist, too. is much concerned
with seeds. The urgent need for genetic conservation is now appreciated
and, central to the developing technology for maintaining germ plasm
collections. are studies on seed viability and longevity (Roberts. 1989).
It can rightly be claimed that a branch of biological science was
founded on studies of seeds. We all know that Mendel used the appearance of
pea seeds in his investigation of inheritance. Now we understand the
biochemical basis of the wrinkled and smooth surface and. more notably, the
r locus has recently been cloned. Mendel's gene from pea seeds can now be
studied with all the sophistication afforded by molecular genetics.
2
THE PRESENT LEADING TO THE FUTURE
In modem times the area of activity covered by the / term seed
research has become fairly well circumscribed to include seed development
and maturation, dormancy and germination, viability and longevity, and
reserve mobilisation. Of course, these are all approachable in appropriately
different ways by ecologists, physiologists, crop scientists, horticulturists,
biochemists and molecular biologists.
It has to be said that much of seed research still takes the form of
descriptive physiology. Cases in point are, dormancy and germination
ecophysiology. Seeds have a remarkable sensitivity to the environment
unrivalled by any other phase in the plant's life history. Seeds can detect
light quality, quantity, photoperiod, temperature, alternations of
temperature, oxygen levels, different chemicals, water precipitation and
water potential (Bewley and Black 1982). All of these can determine whether
or not a seed germinates and the time and place for doing so, so that the
resulting seedling is formed in the most clement situation and favourable
time to support its further development. Such a complex sensitivity
understandably occupies the attention of seed ecologists, through whose
efforts we have already learned much, and we will continue to do so, about
the germination behaviour of very many plant species. Similar approaches
have proved valuable in crop physiology too and we can cite several cases,
for example various species of vegetable seeds, whose responses to the
environment are now well enough understood to enable growers to produce
crops at times and in situations which previously were unsuitable. But
although we know much, in an empirical way, about what determines
germination we have very little understanding of the mechanisms involved.
We cannot explain the temperature regulation of germination and
dormancy, the perception and action of temperature alternations and the
mechanism of action of promotive or inhibitory light. Similarly, although
we can make mathematically-derived predictions about changes in viability
(Ellis, 1988) we still have only a relatively superficial understanding about
the degenerative changes which can occur in a stored seed leading to
diminution in vigour or eventually death.
These remarks are not intended to imply that seed physiologists are
satisfied simply with making descriptions about germination. In some ways,
physiological mechanisms have become clearer. For example, coat effects in
dormancy (leaving aside hard coats which are poorly permeable to water)
are very likely to be due to interference with oxygen access to the embryo;
and indeed, we know that diffusion of this gas across the enclosing tissues is
impeded, sometimes as a result of enzymic oxygen consumption. But the next
step in the syndrome - why this leads to the inhibition of germination that
we call dormancy - is unfortunately still a mystery. Ingenious hypotheses
have been propounded to link the oxygen requirement with the
particularities of metabolism of the embryo that are required for ultimate
axis extension (the culmination of germination) but the final, integrated
explanation still eludes us (Ross, 1984).
The responsibility for progress does not, however, fall entirely on the
seed biologist alone. To understand how a seed germinates I believe that we
need to know more about the regulation of cell elongation, for it is from the
occurrence of this event that we recognise that germination has taken place.
This process, fundamental to plant growth, is still incompletely understood.
Information is slowly being gathered about wall extensibility, cell wall
biochemistry, pH effects, hormonal action, proton secretion, water uptake,
and so on, but we are still far from having a unified picture of cell extension.
When this is available we should then be in a better position to begin to
analyse, with more sophistication than hitherto, the critical events which
3
