Table Of ContentSeed dormancy in grasses
Seed dormancy in grasses
G. M. Simpson
Department of Crop Science and Plant Ecology,
University of Saskatchewan, Saskatoon, Canada
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© Cambridge University Press 1990
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permission of Cambridge University Press.
First published 1990
This digitally printed version 2007
A catalogue record for this publication is available from the British Library
Library of Congress Cataloguing in Publication data
Simpson, G. M.
Seed dormancy in grasses / G. M. Simpson.
p. cm.
Bibliography: p.
Includes index.
ISBN 0 521 37288 7
1. Grasses-Seeds-Dormancy. I. Title.
QK495.G74S613 1990
584'.90446-dc20 89-17255 CIP
ISBN 978-0-521-37288-6 hardback
ISBN 978-0-521-03930-7 paperback
Contents
Preface page vii
Acknowledgements ix
Introduction 1
1 The occurrence of dormancy in the Gramineae 3
1.1 Wild grasses 6
1.2 Forage grasses 7
1.3 Cereal grasses 19
1.4 Weed grasses 30
1.5 Dormancy and persistence of individuals and populations 34
1.6 Xerophytes, mesophytes and hydrophytes 42
1.7 Terminology and definitions of dormancy 43
1.8 A conceptual approach for understanding seed dormancy 48
1.9 A venafatua, a prototype model of grass seed dormancy 59
2 Mutual influences of inflorescence and caryopsis parts on
dormancy 60
2.1 Position of the caryopsis on the parent plant 60
2.2 Lemma, palea, glumes and awns 65
2.3 The grain coat - pericarp and testa 83
2.4 Embryo and scutellum 94
2.5 Interrelation between embryo and maternal storage tissue 106
3 Environmental influences on seed dormancy 114
3.1 Water - liquid and vapour phases 114
3.2 Effects of radiation - heat/cold, light, microwaves, magnetism,
photoperiodism 119
3.3 Latitudinal influences - tropical and temperate zones 158
3.4 Gases - oxygen and anoxia, carbon dioxide, ethylene, volatile
organics; pressure 161
3.5 Growth regulators - promoters, inhibitors, limiting and
allelopathic factors 170
3.6 Soil and agricultural practice 187
Contents
4 Timing of dormancy 195
4.1 Semantic considerations 195
4.2 Timing in the induction, maintenance and release of dormancy 197
5 Modelling the induction, maintenance and termination of dormancy
in grass seeds 207
5.1 Modelling theory for biological systems 207
5.2 A 'black box' perspective of seed behaviour 210
5.3 An energy flow model for grass seed dormancy 218
5.4 Similarity and diversity among dormancy states in grass seeds 224
5.5 Conclusion 228
Bibliography 232
Index 281
VI
Preface
A number of books have been published recently on the subject of
germination physiology of seeds. They often have a chapter or two about
seed dormancy, either to demonstrate the diversity of mechanisms among
seed plants, or to try and simplify the complexity of dormancy mechanisms
by establishing general models. A somewhat different approach is used
here. Firstly, the subject is confined to seed dormancy in grasses. Secondly,
experimental evidence is considered in depth for a single species, the wild
oat (Avena fatua L.), probably the most widely studied species for
understanding seed dormancy in the plant kingdom. The evidence for this
member of the family Gramineae is compared with other examples among
the Gramineae to reach some general conclusions about the nature of seed
dormancy in grasses.
There are several reasons for confining the book to grasses. The grass
family is one of the largest (25 tribes and 600 genera) and most diverse in the
plant kingdom. From a human nutrition perspective it is the most
important family. Grasses are the principal plant life form covering more
than 70% of the land surface of the globe and they are of critical importance
to the stability of the fragile arid and semi-arid zones. While seed dormancy
is of great adaptive significance for survival in nearly all plant species with
seeds, it is also the main reason why grass species cause the most serious
weed problems in cultivated crops around the globe. It is paradoxical that
one of the great achievements of the Neolithic Age was selection against
seed dormancy, so that planted crops would germinate quickly and
uniformly. Today we are only beginning to understand the nature of
dormancy in seeds and how we might use this knowledge to better
advantage. Finally, cereal grass seeds in our present age are the main source
of diet for the majority of the human race. It is therefore for reasons of great
practical, economic and human survival interest that we should fully
vn
Preface
understand the trait of seed dormancy because it is a primary means for
survival of populations, indeed of species, in the plant kingdom.
This book is dedicated to the memory of my colleague for 25 years, the
late Prof. J. M. Naylor, who was a pioneer in the field of seed dormancy
studies. I am indebted to my students and research colleagues who
contributed to our present understanding of seed dormancy in A. fatua. The
pathway to our understanding has not been along a straight line but
something akin to a much compressed helix with much energy spent in
going around the circles.
Vlll
A cknowledgemen ts
Permission for reproduction was granted by Annals of Botany Company
and the editors of Annals of Botany (Figs. 3.1,3.13); Association of Applied
Biologists and editors of Annals of Applied Biology (Fig. 2.S(a));
Cambridge University Press, editors of BioEssays and Dr. A. J. Trewavas
(Fig. 4.1); Crop Science Society of America and editors of Crop Science
(Fig. 2.6); Editorial Office of Physiologia Plantarum (Figs. 3.6, 3.7, 3.12,
3.15); editors of New Phytologist (Fig. 3.8); editor of Phytochemistry (Table
2.3); editors of Proceedings of the Association of Official Seed Analysts
(Figs. 2.8(b), 2.&(c)); editors of Seed Science and Technology (Fig. 3.11);
John Wiley and Sons, New York Ltd., (Symbols of Prof. H. T. Odum in
Figs. 5.7, 5.8); National Research Council of Canada and editor of
Canadian Journal of Botany (Figs. 2.1, 2.2(a), 2.10, 3.2, 3.3, 3.14, 3.16);
Professor I. N. Morrison (Fig. 2.1 (b)) and Professor M. V. S. Raju (Fig.
22(b)). I am particularly grateful to Mr. J. Diduck for help with the
figures, to Dr. F. Turel for editorial asistance and to my wife Margarete for
patience with me during preparation of the manuscript.
IX
