Thomas C. Moore

Biochemistry and Physiology of Plant Hormones

Second Edition

With 177 Figures

Springer-Verlag New York Heidelberg Berlin

London Paris Tokyo Hong Kong

Thomas C. Moore Professor of Botany

Department of Botany and Plant Pathology Oregon State University

Corvallis, Oregon 97331-2902 USA

Library of Congress Cataloging-in-Publication Data Moore, Thomas C.

Biochemistry and physiology of plant hormones. Includes bibliographical references. 1. Plant hormones. I. Title.

QK898.H67M66 1989 581.19'27 89-19737

ISBN-13: 978-1-4612-8193-1 DOT: 10.1007/978-1-4612-3654-2

e-ISBN-13: 978-1-4612-3654-2

Printed on acid-free paper

© 1979, 1989 Springer-Verlag New York Inc. Softcover reprint of the hardcover 2nd edition 1989

All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer-Verlag New York Inc., 175 Fifth Avenue, New York, NY 10010, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use of general descriptive names, trade names, trademarks, etc., in this publication, even if the former are not especially identified, is not to be taken as a sign that such names, as understood by the Trade Marks and Merchandise Marks Act, may accordingly be used freely by anyone.

Typeset by Technical Typesetting Inc., Baltimore, Maryland.

987654321

Biochemistry and Physiology of Plant Hormones

Second Edition

Preface to the First Edition

Biochemistry and Physiology oj Plant Hormones is intended primarily as a textbook or major reference for a one-term intermediate-level or advanced course dealing with hormonal regulation of growth and development of seed plants for students majoring in biology, botany, and applied botany fields such as agronomy, forestry, and horticulture. Additionally, it should be useful to others who wish to become familiar with the topic in relation to their principal student or professional interests in related fields. It is assumed that readers will have a background in fundamental biology, plant physiology, and biochemistry.

The dominant objective of Biochemistry and Physiology oj Plant Hor­mones is to summarize, in a reasonably balanced and comprehensive way, the current state of our fundamental knowledge regarding the major kinds of hormones and the phytochrome pigment system. Written primarily for students rather than researchers, the book is purposely brief. Biochemical aspects have been given priority intentionally, somewhat at the expense of physiological considerations. There are extensive citations of the literature-both old and recent-but, it is hoped, not so much documentation as to make the book difficult to read. The specific choices of publications to cite and illustrations to present were made for different reasons, often to illustrate historical develop­ment, sometimes to illustrate ideas that later proved invalid, occasionally to exemplify conflicting hypotheses, and most often to illustrate the current state of our knowledge about hormonal phenomena. The lists of references at the ends of the chapters, containing some references which are cited and others that are not, are not intended as comprehensive bibliographies of the most recent, or even exclusively the most important, publications on each subject. Each list is intended both to document the text and provide other examples of the extensive literature on each topic.

An explanation should be given for inclusion of the subject matter comprising Chapter 1, since it is acknowledged that many readers will regard Chapter 1 as quite elementary information with which they already are familiar. That is fully to be expected. But for those readers whose background may be deficient, as has been found to be true of a fair percentage of students, Chapter 1 will provide a reasonable overall introduction to and perspective about growth and develop­ment of whole plants throughout ontogeny and set the stage for consideration of hormonal regulation.

Books such as this invariably disappoint some readers, which is to say that they cannot be-perhaps should not even purport to be-all things that all readers might wish or expect. In my judgment, Biochemistry and Physiology oj Plant Hormones most likely might disappoint some readers in each of two ways. First, the book does not contain as lengthy and integrated a discussion either of the physiological roles of the different kinds of hormones or of hormonal

vi Preface to the First Edition

interactions as some readers will wish, although, of course, these topics definitely are covered. To the extent that this is true it is by design. For in my ten years of experience teaching a graduate course in hormonal regulation of plant growth and development, I personally have found that it is more effective to guide students from an information base such as this book provides to a more integrated understanding of regulation of growth and development than to undertake the converse approach. Another way this book might disappoint some prospective users is that it lacks detailed and comprehensive coverage of practical uses of synthetic plant growth regulators, except for synthetic auxins and auxin-type herbicides. Such information is largely beyond the scope of this small volume. Moreover, practical uses of plant growth regulators are covered in many specialized books in agronomy, forestry, and horticulture.

It seems to be a good time in some ways, and not so good a time in other ways, for a new book on the biochemistry and physiology of plant hormones. On the negative side, so far during the decade of the 1970s there seems to be a relative lull in the field as regards dramatic new developments-the "acid growth theory" and other important advancements notwithstanding-compared, let us say, to either of the previous two decades. In view of the relative scarcity of "big news," it could be argued that it is not a particularly good time. But, on the other hand, there is really good and highly significant research going on, and there is a steady output of important new knowledge. The literature-the state of the science-probably is in the best shape ever as far as unequivocal validation of facts and concepts is concerned. It is a time of separation of fact from fiction and devising new approaches to old problems, as well as asking new, important, exciting questions. For these reasons, it seems, therefore, timely for a new book to call attention to this healthy state of the science. In any case, it is an excellent time to be a student at any level of the fascinating subject discussed in Biochemistry and Physiology of Plant Hormones.

Acknowledgments

The real credit for Biochemistry and Physiology of Plant Hormones ultimately should go to the many Plant Physiologists whose research during the last half century disclosed information comprising the book. While too numerous to mention individually, the names of many of these scientists are contained in the literature lists at the ends of the chapters. Certain specitic contributions by particular authors, of course, are acknowledged also in the forms of citations in the text and notations in legends to figures and tables.

The actual writing and production of the book naturally has involved several forms of assistance by many persons, to all of whom I express my sincere gratitude. For directly supplying or assisting to make available certain illustrations, I thank Douglas O. Adams, James D. Anderson, Gerard W. M. Barendse, Michael L. Evans, Peter Hedden, Hans Kende, Anton Lang, A. Carl Leopold, Morris Lieberman, Bernard O. Phinney, Folke Skoog, Nobutaka Takahashi and Jan A. D. Zeevaart. Donald J. Armstrong and Ralph S. Quatrano are thanked for the advice and technical assistance that they provided regarding various topics. I thank Ellen Witt and Leona Nicholson for typing and clerical assistance, and E. Kay Fernald for photographic service. Mark Licker, Science Editor, and Judi Allen, Production Editor, at Springer-Verlag Inc., New York, and their staff were very helpful throughout the review and production processes. Finally, I wish to acknowledge the financial support provided by the National Science Foundation for those of my own investigations during the past fifteen years which are cited in the book.

Corvallis, Oregon January 1979

Thomas C. Moore

Preface to the Second Edition

Ten years ago, when writing the Preface to the first edition of Biochemistry and Physiology of Plant Hormones, I observed that, "The literature (on plant hormones)-the state of the science-probably is in the best shape ever as far as unequivocal validation of facts and concepts is concerned," and further that, "It is a time of separation of fact from fiction and devising new approaches to old problems, as well as asking new, important, exciting questions." Assuredly, those observations are as valid in 1989 as they were in 1979.

Progress during the last decade has not occurred by dramatic major discoveries, but rather by a careful, methodical, and definitive slow pace. The increasingly widespread application of a large number of techniques of plant molecular biology in hormone investigations has enabled many impressive advances, such as (1) elucidation of the nucleotide sequences of phytochrome cDNA clones and deduction of the amino acid sequences by Peter H. Quail and others; (2) isolation and partial characterization of hormone receptors by Michael A. Venis and others; and (3) identification of early gene products resulting from the action of hormones on chromatin by Gretchen Hagen, Tuan­hua David Ho, and others. We seem to be very close to understanding in precise molecular terms the early events in the mechanisms of action of the auxins, gibberellins, and abscisic acid in particular.

Because of the efforts of Anthony J. Trewavas and others, there is a growing appreciation of the concept that plant responses are not correlated only with the amounts or concentrations of endogenous growth substances but as well to the state of sensitivity of the tissues to those substances. The increasing use of mutants in hormone research by Bernard O. Phinney, James B. Reid, and others is enabling an ever closer connection between genes and the hormones they control. Through the efforts of N. Bhushan Mandava. Nobutaka Takahashi, Takao Yokota, and others we are gaining increased appreciation of the brassinosteroids, which, in the" opinion of many plant physiologists, deserve to be treated as a new class of plant growth substances. And problems of long standing continue to receive attention. Kenneth V. Thimann and an associate only recently reported new evidence concerning the role of ethylene in apical dominance, for example.

As exciting and important as the emerging discoveries of plant molecular biology are, the challenge to understand hormonal regulation at the organismal level is ever present. We still seem a long way from understanding the role of hormones in phenomena such as photoperiodic induction of flowering, endogenous circadian and other rhythms, gravitropism, and senescence.

The changes made in the second edition of Biochemistry and Physiology of Plant Hormones are substantial. Part of the former Chapter 1 has been deleted, as that subject matter has become common knowledge; a new chapter on

x Preface to the Second Edition

brassinosteroids has been added, and every other chapter has been revised and updated. The use of references continues to be as it was described in the Preface to the first edition, in that I have not attempted to provide comprehensive lists of references on each subject. The chapters are not comprehensive reviews but rather guides for students to what I believe to be the most relevant and important subject matter on each topic.

Acknowledgments

Many persons have contributed in many ways to the production of the second edition of Biochemistry and Physiology of Plant Hormones, and my sincere gratitude is extended to them all. In particular I wish to thank Donald J. Armstrong, Derek J. Baisted, Ronald C. Coolbaugh, Tuan-hua David Ho, Terri L. Lomax, N. Bhushan Mandava, Noboru Murofushi, B. W. Poovaiah, Peter H. Quail, Nobutaka Takahashi, and Takao Yokota. I thank Ellen Witt for her typing of the manuscript and clerical assistance.

Corvallis, Oregon January 1989

Thomas C. Moore

Contents

CHAPTER 1 INTRODUCTION 1

Fundamental Terms and Concepts Patterns and Kinetics of Growth in Cells, Tissues, Organs, and Whole

Plants 3 Discontinuities in Growth, Growth Periodicities, and Problems of

Relative Growth Rate 12 Mechanisms Controlling Cellular Differentiation 14 Introduction to Plant Hormones 23 References 25

CHAPTER 2 AUXINS 28

Brief History of Discovery 28 Went's A vena Coleoptile Curvature Test 31 Early Isolations of IAA 32 Synthetic Auxins 33 Controversy Surrounding the Use of Certain Chlorophenoxy Acids as

Herbicides and Defoliants 34 Natural Occurrence of Auxins 38 Auxin Biosynthesis 39 "Free" and "Bound" Auxin 42 Destruction of lAA 44 Auxin Transport 47 Relationships between Auxin Content and Growth 54 Correlative Differences in Auxin Relations between Etiolated and

Light-Grown and Dwarf and Normal Plants 58 Mechanism of Auxin Action 61 References 85

CHAPTER 3 GIBBERELLlNS

Brief History of Discovery Chemical Characterization of GAs Natural Occurrence of GAs GA Biosynthesis in Seeds GA Biosynthesis in Systems Other Than Seeds Effects of Light on GA Biosynthesis Role of GAs in Dwarfism Other Aspects of GA Metabolism

94

94 96

104 104 108 113 114 121

xiv Contents

Quantitative Changes in GA Content during Development Sites of GA Biosynthesis in Seed Plants Transport of GA Anatomical and Biophysical Basis of GA-Induced Growth Mechanism of Action of GA References

CHAPTER 4 CYTOKININS

123 134 136 136 139 150

158

History of Discovery 158 Terminology 159 Isolation of Kinetin and the Search for Other Naturally Occurring

Cytokinins 159 Discovery of Natural Cytokinins 160 Effects of Cytokinins and Other Hormones in Organisms Other Than

Seed Plants 166 Structure/Activity Relationships of the Cytokinins 167 Biosynthesis and Metabolism 170 Auxin and Cytokinin Biosynthesis in Crown Gall Tumors 174 Mechanisms of Origin in tRNA 174 Metabolic Consequences of the Presence of Cytokinins in tRNA 178 Hormonal Activity of Free Cytokinins 179 Cytokinin Binding Protein 180 Effects on Moss Protonemata 181 Some Physiological Effects on Seed Plants 184 Translocation 188 References 189

CHAPTER 5 ABSCISIC ACID AND RELATED COMPOUNDS 196

Introduction 196 History of Discovery 197 Chemical Characterization 201 Biosynthesis and Other Features of Metabolism 202 Natural Occurrence of ABA 207 Physiological Effects 208 State of Chromatin in Dormant Tissues and the Mechanism of Action of

ABA 220 References 221

CHAPTER 6 ETHYLENE

Historical Background Ethylene and Fruit Ripening Interaction between Auxin and Ethylene

228

228 229 235

Contents

Ethylene and Apical Dominance Inhibition of Root Growth and Role in Root Gravitropism Role in Emergence of Dicot Seedlings Role in Abscission Effects of Ethylene on Planes of Cell Expansion Other Effects of Ethylene Ethylene Biosynthesis and Mechanism of Action Ethylene Receptor References

CHAPTER 7 BRASSINOSTEROlDS

Introduction Brief History of Discovery Chemistry of BRs Natural Occurrence of BRs Biological Effects Effects on Nucleic Acid and Protein Metabolism Practical Applications in Agriculture Some Problems and Prospects References

CHAPTER 8 PHYTOCHROME

Introduction History of Discovery and Modern Description Sequence Analysis of Phytochrome Occurrence, Distribution, and Intracellular Localization Induction-Reversion versus High Irradiance Responses Non-Phytochrome-Mediated Photoresponses to Blue Light Introduction to Mechanism of Phytochrome Action Phytochrome Action in Nonphotoperiodic Photoresponses Phytochrome and Photoperiodic (Flowering) Responses Calcium Messenger System in Plants References

Index

xv

238 239 240 242 244 244 248 249 250

255

255 255 256 256 260 263 263 264 264

267

267 267 275 278 280 281 283 284 293 308 312

321