rv^ k ^ Physiology of CM'^Rchids llmwa^llilm^ VOAfcwll.WH.fcng World Scientific

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1 rv^ k ^ Physiology of CM'^Rchids llmwa^llilm^ VOAfcwll.WH.fcng World Scientific

2 Che Physiology op *CRopic<\( ORchids m Relation ro rhe IndusrRy

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4 The Physiotogy of rropicd( ORchids m Retorion ro rhc IndustRy CS.HewM.W.H.Yong Department of Botany National University of Singapore World Scientific Singapore New Jersey London Hong Kong

5 Published by World Scientific Publishing Co. Pte. Ltd. P O Box 128, Farrer Road, Singapore USA office: Suite IB, 1060 Main Street, River Edge, NJ UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE Library of Congress Cataloging-in-Publication Data Hew, Choy Sin. The physiology of tropical orchids in relation to the industry / C. S. Hew & J. W. H. Yong. p. cm. Includes bibliographical references and index. ISBN ISBN (pbk.) 1. Orchid culture ~ Asia, Southeastern. 2. Orchids Asia, Southeastern Physiology. 3. Orchid culture Tropics. 4. Orchids - - Tropics--Physiology. I. Yong, J. W. H. (Jean W. H.) II. Title. SB409.5.A785H '344--dc CIP British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. Copyright 1997 by World Scientific Publishing Co. Pte. Ltd. Allrights reserved. This book, or parts thereof, may not be reproduced in anyformor by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the Publisher. For photocopying of material in this volume, please pay a copying fee through the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, USA. In this case permission to photocopy is not required from the publisher. Printed in Singapore by Uto-Print

Foreword I take great pleasure in writing the foreword to this book, The Physiology of Tropical Orchids in Relation tt the Industry, which relates to a thriving industry.

6 Foreword I take great pleasure in writing the foreword to this book, The Physiology of Tropical Orchids in Relation tt the Industry, which relates to a thriving industry. Cut-flower orchid production and potted orchid cultivation have been a mainstay agro-industry in South East Asia and indeed, throughout the world. In order to sustain and nurture the growth of the industry, new and improved agro-technology is needed. The scientific disciplines that contribute to improving orchid production technology have been developed to such sophisticated and specialised levels that the trial-and-error approach generally adopted by orchid hobbyists and commercial growers can no longer be depended upon to meet the demands of a global cut-flower market. Scientific studies on orchid biology are paving the way for the orchid industry. If orchid researchers, hobbyists and commercial growers can be provided with convenient access to more recent research findings, clearly these would greatly enhance their efforts in meeting the challenge of improving the production technology. There are very few orchid books in the world that deal specifically with the scientific aspects of orchid biology and cultivation. In South East Asia, there is not, as yet, an organised source of tropical orchid literature suited for the study of orchid biology and the direct application of this knowledge to serve the industry. The contribution of Professor Hew Choy Sin and Mr Jean Yong to tropical orchid biology and industry is therefore both valuable and timely. This book is written in response to the growing demand for an orchid physiology book with a tropical perspective both in Singapore and her neighbouring South East Asian countries. This pioneering book aims at defining the status of our present knowledge of orchid physiology, with an emphasis on tropical orchids, and considers how existing knowledge can be put to greater and more practical use. The authors have identified the gaps in our knowledge and discussed how V

7 vi Foreword these gaps can best be filled through additional research. The Physiology of Tropical Orchids in Relation to the Industry will be an important and useful source of information for university students, orchid researchers and commercial orchid growers. I congratulate the authors for sharing their expertise. Professor Leo Tan Director National Institute of Education Nanyang Technological University President Singapore National Academy of Science

8 Preface The fundamental aim underlying the writing of this book is the desire to provide a comprehensive and exclusive text of tropical orchid physiology relevant to commercial growers, research workers and graduate students. Over the past few decades, the orchid industry is growing at a steady pace in the South East Asian and East Asian regions, and it is becoming an essential export item in some Asian countries. To maintain this progress, there is an urgent need for a comprehensive book that is relevant to the region to guide orchid growers in improving their cultivation and management skills, and to guide new students in understanding orchid physiology. There are scientific books written on orchids that are very good, in our opinion, such as The Orchids: A Scientific Survey, Orchids: Scientific Studies, Fundamentals of Orchid Biology and the book series Orchid Biology: Reviews and Perspectives. We hope that this book would complement the existing scientific literature available to improve orchid cultivation and to set new research agenda especially in the tropics. The bulk of the text is based on the research effort of past graduate students, research associates and visiting scientists working with Professor C. S. Hew in Nanyang University and later, in the National University of Singapore. The duration of orchid research spans 26 years, first started in 1970, and is still been actively pursued till today. To fill the relevant gaps in information and for comparison purposes, relevant publications from other research groups are also included. This inevitably includes some discussion of the temperate orchids. The idea of this book was conceptualized when we were making a computer database of publications related to orchid physiology in We decided to take a step further and to produce an integrated and unifying theme of tropical orchid physiology with a clearly written factual text and illustration. The present cultural technology has given growers and hobbyists the opportunity to grow vii

9 Vlll Preface orchids anywhere in the world. As such, the strict demarcation of whether an orchid is a tropical or a temperate one is no longer possible. We proposed that the term "Tropical orchids" be perceived in a broad sense. There are nine chapters in this book. Each chapter is designed to provide a comprehensive, up-to-date information on an aspect of orchid physiology. References in the text are reduced to include only the leading authorities in the appropriate fields. Whilst it is recognised that the study of biological science follows no set pattern, the content of different chapters is written using a similar approach. Unlike the earlier chapters, Chap. 9 is a unique chapter where it deals with the problems and recent advances in orchid tissue culture. This chapter looks at the problems created by growing orchids in an artificial environment and offers practical solutions and new research directions to improve in vitro orchid growth. C.S.Hew&J.W.H.Yong Singapore, March 1996

10 Contents Foreword Preface Acknowledgements v vii xiv 1. The Relevance of Orchid Physiology to the Industry Introduction Orchid Cultivation and Industry How Basic Orchid Physiology Can Help the Industry Concluding Remarks 8 2. A Brief Introduction to Orchid Morphology and Nomenclature Introduction Growth Habit Orchid Plant Parts 13 Pseudobulbs 13 Flowers 15 Seeds 22 Leaves 22 Roots Growth Cycle of Orchids Under Greenhouse Conditions Nomenclature 30 Species 30 Hybrid Summary Photosynthesis Introduction Photosynthetic Pathways 37 IX

11 X Contents 3.3. What is 5 13 C Value? Patterns of C0 2 Fixation in Orchids 45 Thin-leaved orchids 45 Thick-leaved orchids Photosynthetic Characteristics of Non-Foliar Green Organs 52 Aerial roots 54 Stems 61 Pseudobulbs 62 Flowers and fruit capsules 64 Varying S 13 C values in non-foliar green organs Factors Affecting Photosynthesis 68 Effects of light 68 Effects of age 69 Effects of water stress 75 Effects of temperature 77 Effects of sink demands 81 Effects of pollutants 82 Effects of virus infection 84 Effects of elevated carbon dioxide Concluding Remarks Summary Respiration Introduction Respiratory Processes Respiration in Plant Parts 96 Protocorms and Seedlings 96 Leaves 99 Flowers 101 Roots Respiratory Drift During Flower Development Photorespiration Other Oxidases in Relation to Orchid Respiration Concluding Remarks Summary 123

12 Contents XI 5. Mineral Nutrition Introduction Mineral Requirements and Tissue Analysis Fertiliser Application Practices 136 Effects of organic fertilisers on orchid growth 138 Effects of mulching on orchid growth 139 Effects of inorganic fertilisers on orchid growth Foliar Application and Root Absorption Ion Uptake 152 Ion uptake by orchid tissues 152 Ion uptake by orchid roots Concluding Remarks Summary Control of Flowering Introduction Differentiation of Flower Bud Factors Affecting Flower Induction 170 Juvenility in orchids 172 Response to low temperature 172 Photoperiodic response 177 Hormonal control Seasonality in Flowering Application of Flower Induction at the Commercial Level Bud Drop Controlling Orchid Flower Production Concluding Remarks Summary Partitioning of Assimilates Introduction The Source-Sink Concept of Phloem Translation 198 Sources and sinks 199 Phloem loading 200

13 Xll Contents Along the path 201 Phloem unloading Patterns of Assimilate Movement in Most Higher Plants Patterns of Assimilate Movement in Tropical Orchids 204 Assimilate partitioning in the sympodial orchids 205 Assimilate partitioning in the monopodial orchids Import of Assimilates by Mature Orchid Leaves The Role of Non-Foliar Green Organs in Assimilate Partitioning Improving the Harvestable Yield of Orchids Concluding Remarks Summary Flower Senescence and Postharvest Physiology Introduction Senescence in Plants Growth and Development of Orchid Flower and Inflorescence Flower Senescence in Orchids 254 Post-pollinated phenomena 254 Ethylene and senescence Postharvest Handling of Cut-Flowers 267 Preharvest conditions 269 Extension of vase-life 270 Formulation of various solutions 271 Bud opening Storage and Transport 276 Low-temperature storage 277 Hypobaric storage/controlled storage Concluding Remarks Summary 280

14 Contents Xlll 9. Recent Advances in Orchid Tissue Culture Introduction Factors Affecting Orchid Growth in Vitro 289 Sugar 290 Carbon dioxide 292 Ethylene 293 Nitrogen sources 296 Light 297 Other factors Improving Orchid Cultures 300 Gas-permeable culture system 300 Alternative supporting media 306 Carbon dioxide enrichment 308 Development of a flow system In-Vitro Flowering Thin-Section Culture Synthetic Seeds Concluding Remarks Summary 317 Subject Index Plant Index

15 Acknowledgements We thank Mrs. Hew Yik Suan and Miss Gan Kim Suan for their help in preparing and editing the manuscript. The technical support of Mr. Ong Tang Kwee over the years is greatly appreciated. We are grateful to the following for their help in many ways: Multico Orchids Private Limited, Lee Foundation, Professor M. Tanaka, Dr. Hugh Tan and Dr. S. C. Wong. We are grateful to the publishers and journals for allowing us to reproduce their illustration and acknowledgement is given beside the illustration. The strong institutional support provided for orchid research by Nanyang University, and later, the National University of Singapore, is acknowledged. XIV

A FIRST COURSE IN INTEGRAL EQUATIONS

A FIRST COURSE IN INTEGRAL EQUATIONS This page is intentionally left blank A FIRST COURSE IN INTEGRAL EQUATIONS Abdul-M ajid Wazwaz Saint Xavier University, USA lib World Scientific 1M^ Singapore New Jersey