Table Of ContentPLANT HORMONES AND THEIR ROLE IN PLANT GROWTH AND
DEVELOPMENT
The cover drawing shows four genetic lines of pea differing in internode length
and gibberellin (GA) content in their vegetative tissue. Left to right: Nana (na):
an ultradwarf containing no detectable GAs; Dwarf (Na Ie) containing GA2o;
Tall (Na Ie) containing GAl; Slender (Ia cryS): an ultratall also with no detect
able GAs (see chapter E4). The inset formula is that for GAl'
(Drawing by Barbara Bernstein from a photograph by Peter J. Davies)
Plant Hormones and their Role in
Plant Growth and Development
Edited by
PETER J. DAVIES
Section of Plant Biology
New York State College of Agriculture and Life Sciences
Cornell University, Ithaca, New York, USA
1987 MARTINUS NIJHOFF PUBLISHERS
a member of the KLUWER ACADEMIC PUBLISHERS GROUP
DORDRECHT / BOSTON / LANCASTER
Distributors
for the United States and Canada: Kluwer Academic Publishers, P.O. Box 358,
Accord Station, Hingham, MA 02018-0358, USA
for the UK and Ireland: Kluwer Academic Publishers, MTP Press Limited,
Falcon House, Queen Square, Lancaster LAI lRN, UK
for all other countries: Kluwer Academic Publishers Group, Distribution Center,
P.O. Box 322, 3300 AH Dordrecht, The Netherlands
Library of Congress Cataloging in Publication Data
Plant hormones and their role in plant growth and
development.
Includes bibliographies and index.
1. Plant hormones. 2. Growth (Plants) 3. P1ants--
Development. I. Davies, Peter J.
QK731.P595 1987 581.3'1 87-5669
ISBN-13:978-90-247-3498-6 e-ISBN-13:978-94-009-3585-3
DOl: 10.1007/978-94-009-3585-3
Book information
Set in type by the Media Services Department, New York State College of Agri
culture and Life Sciences, Cornell University, Ithaca, New York 14853, USA.
Copyright
© 1987 by Martinus Nijhoff Publishers, Dordrecht.
Softcover reprint of the hardcover 1st edition 1987
All rights reserved. No part of this publication may be reproduced, stored in a
retrieval system, or transmitted in any form or by any means, mechanical,
photocopying, recording, or otherwise, without the prior written permission of
the publishers,
Martinus Nijhoff Publishers, P.O. Box 163, 3300 AD Dordrecht,
The Netherlands.
PREFACE
Plant hormones playa crucial role in controlling the way in which
plants grow and develop. While metabolism provides the power and
building blocks for plant life it is the hormones that regulate the speed of
growth of the individual parts and integrate these parts to produce the
form that we recognize as a plant. In addition, they playa controlling role
in the processes of reproduction. This book is a description of these
natural chemicals: how they are synthesized and metabolized; how they
work; how we measure them; and a description of some of the roles they
play in regulating plant growth and development. This is not a conference
proceedings but a selected collection of newly written, integrated,
illustrated reviews describing our knowledge of plant hormones and the
experimental work which is the foundation of this knowledge.
The information in these pages is directed at advanced students and
professionals in the plant sciences: botanists, biochemists, molecular
biologists, or those in the horticultural, agricultural and forestry sciences.
It is intended that the book should serve as a text and guide to the
literature for graduate level courses in the plant hormones, or as a part of
courses in plant or comparative development. Scientists in other
disciplines who wish to know more about the plant hormones and their
role in plants should also find this volume invaluable It is hoped that
anyone with a reasonable scientific background can find valuable
information in this book expounded in an understandable fashion.
Gone are the days when one person could write a comprehensive book
in an area such as plant hormones. I have thus drawn together a team of
forty-one experts who have individually or jointly written about their own
area. At my direction they have attempted to tell a story in a way that
will be both informative and interesting. Their styles and approaches
vary, because they each have a tale to tell from their own perspective. The
choice of topics has been my own. Within each topic the coverage and
approach has been decided by the authors. While the opinions expressed
by the authors are their own, they are, in general, also mine because I
knew their perspective before I invited them to join the project.
A volume such as this cannot be encyclopedic. For this sort of
coverage the reader is refered to the Encyclopedia of Plant Physiology
(new series, volumes 9, 10, and 11). Nevertheless, we have covered the
majority of topics in which active research is taking place. The author of
each chapter has provided a set of references which will guide the reader
to more detailed recent reviews, as well as classical papers and the latest
advances in that area. The number of references has, however, been
limited so as not to disrupt the narrative excessively. The subject matter
ranges from basic biochemistry and molecular biology to the use of
natural and synthetic plant growth regulators in agriculture and
horticulture, with a preview of the potential manipulation of plant
hormone content via prokaryotes. It is most noticeable as one progresses
through the chapters that while we know a lot, though certainly not
everything, about the action of plant hormones at the molecular and
cellular level, our knowledge of hormones in the whole plant functions of
importance to agriculture and horticulture, such in flowering,
tuberization and dormancy, is at a very superficial level. Only when such
systems are fully understood can we hope to manipulate plant growth to
human advantage.
I would like to thank the authors who made this volume possible. The
production of the final copy was accomplished from author-submitted
computer discs by Marilyn Kelly, Donna Vantine, Anne Mac Arthur, and
Parrish Kelley at Cornell University Media Services, whose efforts are
gratefully acknowledged. I would also like to thank Linda DeNoyer for
the translation of several computer discs and for assistance in the
preparation of the index and Barbara Bernstein for preparing some of the
artwork.
Peter J. Davies
Ithaca, New York
December 1986
VI
PLANT HORMONES
AND THEIR ROLE IN PLANT GROWTH
AND DEVELOPMENT
Contents
A. INTRODUCTION
1 The plant hormones: Their nature, occurrence, and functions
P.J. Davies 1
2 The plant hormone concept: Transport, concentration, and
sensitivity-P.J. Davies 12
B. HORMONE SYNTHESIS AND METABOLISM
1 Auxin biosynthesis and metabolism
D.M. Reinecke and R.S. Bandurski 24
2 Gibberellin biosynthesis and metabolism-V.M. Sponsel 43
3 Cytokinin biosynthesis and metabolism-B.A. McGaw 76
4 Biosynthesis and metabolism of ethylene
T.A. McKeon and S.F. Yang 94
5 Abscisic acid biosynthesis and metabolism-D.C. Walton 113
~ HOW HORMONES WORK
1 Auxin and cell elongation-R.E. Cleland 132
2 The control of gene expression by auxin-G. Hagen 149
3 Gibberellin and abscisic acid in germinating cereals
J. V. Jacobsen and P.M. Chandler 164
4 Hormone binding and its role in hormone action
K.R. Libbenga and A.M. Mennes 194
D. HORMONE ANALYSIS
1 Instrumental methods of plant hormone analysis-R. Horgan 222
2 Immunoassay methods of plant hormone analysis
V.C. Pence and J.L. Caruso 240
E. THE FUNCTIONING OF HORMONES IN PLANT GROWTH
AND DEVELOPMENT
1 Ethylene in plant growth, development, and
senescence-M.s. Reid 257
2 Polyamines as endogenous growth regulators
A. W. Galston and R. Kaur-Sawhney 280
3 Gibberellins and plant cell elongation-J-P. Metraux 296
4 The genetic control of growth via hormones-J.B. Reid 318
5 Auxin transport-P.H. Rubery 341
6 The induction of vascular tissues by auxin-R. Aloni 363
7 Hormones and the orientation of growth
P.B. Kaufman and I. Song 375
8 Hormonal regulation of apical dominance-l.A. Tamas 393
9 Hormones as regulators of water balance-T.A. Mansfield 411
10 Hormones and reproductive development-J.D. Metzger 431
11 Hormones and heterosis in plants
S.B. RoodandR.P. Pharis 463
12 The role of hormones in photosynthate partitioning and
seed filling-M.L. Brenner 474
13 The role of hormones during seed development
R.S. Quatrano 494
14 The role of hormones in potato (Solanum tuberosum L.)
tuberization-E.E. Ewing 515
15 The hormonal control of bud and seed dormancy
in woody plants-L.E. Powell 539
16 Hormones in plant senescence-J.J. Goldthwaite 553
17 Postharvest hormone changes in vegetables and fruit
P.M. Ludford 574
18 Hormones in tissue culture and micropropagation
A.D. Krikorian, K. Kelly andD.L. Smith 593
19 Natural and synthetic growth regulators and their use in
horticultural and agronomic crops-T.J. Gianfagna 614
20 Genes specifying auxin and cytokinin biosynthesis
in prokaryotes-R.O. Morris 636
INDEX 656
A. INTRODUCTION
AI. The Plant Hormones: Their Nature,
Occurrence, and Functions
PeterJ. Davies
Section of Plant Biology, Cornell University, Ithaca, Ne w York 14853,
USA.
INTRODUCTION
The Meaning of a Plant Hormone
Plant hormones are a group of naturally occurring, organic substances
which influence physiological processes at low concentrations. The
processes influenced consist mainly of growth, differentiation and
development, though other processes, such as stomatal movement, may
also be affected. Plant hormones have also been refered to as
'phytohormones' though this term is seldom used.
The term "hormone" comes originally from the Greek and is used in
animal physiology to denote a chemical messenger. Its original use in
plant physiology was derived from the mammalian concept of a hormone.
This involves a localized site of synthesis, transport in the bloodstream to
a target tissue, and the control of a physiological response in the target
tissue via the concentration of the hormone (14). Auxin was similarly
thought to produce a growth response at a distance from its site of
synthesis, and thus to fit the definition of a transported chemical
messenger. It is now clear that plant hormones do not fulfil the require
ments of a hormone in the mammalian sense. In a controversial article
that has caused a rethinking of much dogma in the area, Trewavas (14)
has argued that plant physiologists have been so concerned with making
plant hormones fit the same characteristics as animal hormones that we
have overlooked their unique characteristics in controlling growth and
development. The synthesis of plant hormones may be localized (as
occurs for animal hormones) but may also occur in a wide range of tissues,
or cells within tissues. While they may be transported and have their
action at a distance this is not always the case. They may also act in the
tissue in which they are synthesized or even within the same cell. At one
1
Nature, occurrence and functions
extreme we find the transport of cytokinins from roots to leaves where
they prevent senescence and maintain metabolic activity, while at the
other extreme the production of the gas ethylene may bring about changes
within the same tissue, or within the same cell, where it is synthesized.
Thus, we must abandon the concept of transport as being an essential
property of a plant hormone. Trewavas has also strongly argued that
control is not by concentration but by a change in sensitivity of the tissue
to the compound. This issue is more hotly debated and will be discussed
later. However, as a result of the lack of direct rigid parallels with animal
hormones he has argued that we should abandon the term "plant
hormone". In a rebuttal Cleland (15) has characterized this argument as
"semantic quibbling". Trewavas suggests we should replace the term
hormone with "plant growth substance".! The disadvantage of this name,
besides being cumbersome and containing the rather vague term
"substance," is that it does not describe fully what these natural
regulators do. Growth is only one of the many processes influenced.
Changing the name to "plant growth and development substances"
becomes even more awkward and still may not cover all cases. While the
term plant growth regulator is a little more precise this term has been
(unfortunately?) usurped by the agrichemical industry to denote synthetic
plant growth regulators (see chapter E19) as distinct from endogenous
growth regulators. Thus the term plant growth regulator is largely
unused in reference to endogenous regulators of growth and
differentiation. One could invent an entirely new single word name for
this group of compounds but, rather like the international language
Esperanto, that would seem to be unlikely to catch on in the face of over
fifty years of habit. Thus we are left with the imperfect term "plant
hormone" and all that it implies. We must break with the characteristics
expected of animal hormones: plant hormones are a unique set of
compounds, with unique metabolism and properties, that form the subject
of this book. Their only universal characteristics are that they are
natural compounds in plants with an ability to affect physiological
processes at concentrations far below those where either nutrients or
vitamins would affect these processes. In fact, this notion of a plant
hormone is much closer to the meaning of the Greek origin of the word (to
set in motion or to stimulate) than is the current meaning of the word
hormone used in the context of animal physiology. The Greek origin of the
word does not have in it the implicit idea of either transport or action at a
distance. The term plant hormones has, therefore, been retained in this
book.
1 The international society for the study of plant hormones is named the "International
Plant Growth Substance Association" (IPGSA).
2
