Plant Architecture and Its Manipulation Annual Plant Reviews A series for researchers and postgraduates in the plant sciences. Each volume in this series focuses on a theme of topical importance, and emphasis is placed on rapid publication. Editorial Board: Professor Jeremy A. Roberts (Editor-in-Chief), Plant Science Division, School of Bio- sciences, University of Nottingham, Sutton Bonington Campus, Loughborough, Leicestershire LE12 5RD, UK; Professor Hidemasa Imaseki, Obata-Minami 2 4 19, Moriyama-ku, Nagoya 463, Japan; Dr Michael T. McManus, Institute of Molecular BioSciences, Massey University, Palmerston North, New Zealand; Dr Jocelyn K.C. Rose, Department of Plant Biology, Cornell University, Ithaca, New York 14853, USA. Titles in the series: 1. Arabidopsis Edited by M. Anderson and J.A. Roberts 2. Biochemistry of Plant Secondary Metabolism Edited by M. Wink 3. Functions of Plant Secondary Metabolites and their Exploitation in Biotechnology Edited by M. Wink 4. Molecular Plant Pathology Edited by M. Dickinson and J. Beynon 5. Vacuolar Compartments Edited by D.G. Robinson and J.C. Rogers 6. Plant Reproduction Edited by S.D. O’Neill and J.A. Roberts 7. Protein–Protein Interactions in Plant Biology Edited by M.T. McManus, W.A. Laing and A.C. Allan 8. The Plant Cell Wall Edited by J.K.C. Rose 9. The Golgi Apparatus and the Plant Secretory Pathway Edited by D.G. Robinson 10. The Plant Cytoskeleton in Cell Differentiation and Development Edited by P.J. Hussey 11. Plant–Pathogen Interactions Edited by N.J. Talbot 12. Polarity in Plants Edited by K. Lindsey 13. Plastids Edited by S.G. Møller 14. Plant Pigments and their Manipulation Edited by K.M. Davies 15. Membrane Transport in Plants Edited by M.R. Blatt 16. Intercellular Communication in Plants Edited by A.J. Fleming 17. Plant Architecture and its Manipulation Edited by C.G.N. Turnbull Plant Architecture and its Manipulation Edited by Colin G.N. Turnbull Department of Agricultural Sciences Imperial College London Wye Campus, Kent UK © 2005 by Blackwell Publishing Ltd Editorial Offices: Blackwell Publishing Ltd, 9600 Garsington Road, Oxford OX4 2DQ, UK Tel: ϩ44 (0)1865 776868 Blackwell Publishing Asia Pty Ltd, 550 Swanston Street, Carlton, Victoria 3053, Australia Tel: ϩ61 (0)3 8359 1011 ISBN 1-4051-2128-9 Published in the USA and Canada (only) by CRC Press LLC, 2000 Corporate Blvd., N.W., Boca Raton, FL 33431, USA Orders from the USA and Canada (only) to CRC Press LLC USA and Canada only: ISBN 0-8493-2353-3 The right of the Author to be identified as the Author of this Work has been asserted in accordance with the Copyright, Designs and Patents Act 1988. 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, electronic, mechanical, photocopy- ing, recording or otherwise, except as permitted by the UK Copyright, Designs and Patents Act 1988, without the prior permission of the publisher. This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use. Trademark notice: Product or corporate names may be trademarks or registered trade- marks, and are used only for identification and explanation, without intent to infringe. First published 2005 Library of Congress Cataloging-in-Publication Data: A catalog record for this title is available from the Library of Congress British Library Cataloguing-in-Publication Data: A catalogue record for this title is available from the British Library Set in 10/12 pt Times by Newgen Imaging Systems (P) Ltd, Chennai, India Printed and bound in India by Replika Press Pvt Ltd, Kundli The publisher’s policy is to use permanent paper from mills that operate a sustainable forestry policy, and which has been manufactured from pulp processed using acid-free and elementary chlorine-free practices. Furthermore, the publisher ensures that the text paper and cover board used have met acceptable environmental accreditation standards. For further information on Blackwell Publishing, visit our website: www.blackwellpublishing.com Contents Contributors xi Preface xiii 1 Cellular architecture: Regulation of cell size, cell shape and organ initiation 1 ANDREW J. FLEMING 1.1 Introduction 1 1.2 Growth and cell proliferation are related but separable components controlling cellular architecture 1 1.3 Meristems as a source of cells in the plant 3 1.4 Patterning of cellular architecture 6 1.5 The cellular decision to proliferate or not to proliferate 8 1.6 The cytoskeleton as an intermediary in the regulation of cellular architecture 11 1.7 The supracellular organisation of growth 15 1.7.1 The relationship between cell architecture and organ size and shape 15 1.7.2 Cell division and organ initiation 17 1.7.3 Coordination of organ initiation 18 1.8 Conclusions 19 2 Leaf architecture: Regulation of leaf position, shape and internal structure 23 JULIE KANG and NANCY G. DENGLER 2.1 Introduction 23 2.2 Phyllotaxis 24 2.2.1 Helical phyllotaxis and the Fibonacci series 26 2.2.2 Regulation of phyllotaxis 26 2.3 Leaf initiation 29 2.3.1 Role of expansin in leaf initiation 29 2.3.2 Molecular markers of leaf initiation 30 2.4 Development of leaf symmetry 30 2.4.1 Adaxial domain 31 2.4.2 Abaxial domain 33 2.5 Development of simple leaf architecture 33 2.5.1 Dicots 33 2.5.2 Monocots 34 2.6 Development of compound leaf architecture 35 2.6.1 Molecular regulation of blastozone activity 38 2.6.1.1 KNOX genes 38 vi CONTENTS 2.6.1.2 Phantastica 38 2.6.1.3 Floricaula, Leafy, Unifoliata and Falsiflora 39 2.7 Leaf expansion 41 2.8 Development of internal leaf architecture 43 2.8.1 Cell division and tissue patterning 44 2.8.2 Vascular pattern formation 45 2.8.3 Epidermal cell pattern 46 2.8.3.1 Stomate pattern 47 2.8.3.2 Trichome pattern 48 2.9 Concluding remarks 48 3 Shoot architecture I: Regulation of stem length 57 JOHN J. ROSS, JAMES B. REID, JAMES L. WELLER and GREGORY M. SYMONS 3.1 Introduction 57 3.2 Plant growth hormones and genes regulating their levels 57 3.2.1 Auxin, gibberellin and brassinosteroid 57 3.2.2 Ethylene and cytokinin 65 3.3 Hormone signal transduction 65 3.4 Dwarfism not mediated by hormones 66 3.5 The green revolution 67 3.6 Interactions between hormones 70 3.7 Regulation of stem length by environmental factors 73 3.7.1 Effects of light on stem growth 73 3.7.1.1 De-etiolation 74 3.7.1.2 Shade-avoidance 76 3.7.1.3 Photoperiod 78 3.7.2 Mediation of light effects by hormones 78 3.7.3 Effects of other factors, including flooding and decapitation/grazing 83 3.8 Concluding discussion – are hormones regulators of plant growth or merely permissive factors? 84 4 Shoot architecture II: Control of branching 92 COLIN G.N. TURNBULL 4.1 Introduction 92 4.1.1 Species differ widely in propensity for branching during normal ontogeny 92 4.1.2 Responses to decapitation 93 4.2 Branch positions and morphologies 95 4.2.1 Developmental zones 95 4.2.2 Shoot dimorphism: orthotropic vs. plagiotropic development 96 4.2.3 Relative timing: proleptic vs. sylleptic branching 98 4.2.4 Reiteration: monopodial vs. sympodial systems 99 4.3 Bud initiation 101 4.3.1 Bud initiation genes 103 4.3.1.1 Lateral suppressor (Ls) 103 CONTENTS vii 4.3.1.2 Blind (Bl) 103 4.3.1.3 Revoluta (REV ) 104 4.3.1.4 LAX and SPA 104 4.3.1.5 SAX loci 104 4.3.1.6 Interaction of initiation genes 105 4.4 Bud dormancy and branch outgrowth 105 4.4.1 Branch outgrowth genes 106 4.4.2 Physiology of branching mutants 107 4.4.3 Shoot branching and apical dominance models 110 4.4.4 Branching control: more than auxin and cytokinin 112 4.5 Environmental influences 113 4.5.1 Light effects 113 4.5.1.1 Photoperiod 113 4.5.1.2 Light intensity and spectrum: shade and neighbour responses 114 4.5.2 Nutrition 114 4.6 Conclusions and prospects 115 5 Floral architecture: Regulation and diversity of floral shape and pattern 121 ELENA M. KRAMER 5.1 Introduction 121 5.2 Phyllotaxy and merosity 121 5.2.1 Genetic control of floral phyllotaxy 123 5.2.2 Genetic control of merosity 124 5.2.3 Evolutionary aspects of phyllotaxy and merosity 125 5.3 Floral symmetry 126 5.3.1 Genetic control of floral symmetry 127 5.3.2 Evolutionary aspects of floral symmetry 128 5.4 Floral organ identity 130 5.4.1 Genetic control of floral organ identity 130 5.4.2 Evolutionary aspects of floral organ identity 133 5.4.2.1 Patterns of gene duplication and their functional significance 134 5.4.2.2 Patterns of gene expression and their morphological significance 136 5.5 Elaboration of organ identity 138 5.6 Sex determination as a modification of floral architecture 139 5.7 Future perspectives 140 6 Inflorescence architecture 149 ANUJ M. BHATT 6.1 Determinate and indeterminate inflorescence types 149 6.2 Simple and compound inflorescences 150 6.2.1 Simple inflorescences 150 6.2.2 Compound inflorescences 152 6.3 Growth and branching patterns of shoots 152 6.4 Vegetative to reproductive transition 154 viii CONTENTS 6.5 Meristem identity 155 6.5.1 Shoot/inflorescence meristem identity 155 6.5.2 Flower meristem identity genes 156 6.6 Genetic regulation of inflorescence architecture 157 6.6.1 Maize inflorescence development 157 6.6.2 Pea mutants 163 6.6.3 Tomato inflorescence development 165 6.6.4 Petunia inflorescence development 166 6.6.5 Capitulum development 168 6.6.6 Arabidopsis inflorescence development 169 6.7 Evolution of inflorescence architecture 174 7 Root architecture 182 J.