CRC REVIVALS CRC REVIVALS A. Mozafar Plant Vitamins Plant Vitamins Agronomic, Physiological, and Nutritional Aspects A. Mozafar ISBN 978-1-315-89670-0 ,!7IB3B5-ijghaa! www.crcpress.com PLANT VITAMINS Agronomic, Physiological, and Nutritional Aspects A. Mozafar Boca Raton London New York CRC Press is an imprint of the Taylor & Francis Group, an informa business First published 1994 by CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 Reissued 2018 by CRC Press © 1994 by CRC Press, Inc. CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. 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CCC is a not-for-profit organization that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging-in-Publication Data Mozafar, Ahmad. Plant vitamins: agronomic, physiological, and nutritional aspects / Ahmad Mozafar. p. cm. Includes bibliographical references and index. ISBN 0-8493-4734-3 1. Plant vitamins. I. Title. QK898.V5M63 1993 581.19’26—dc20 93-8744 A Library of Congress record exists under LC control number: 93008744 Publisher’s Note The publisher has gone to great lengths to ensure the quality of this reprint but points out that some imperfections in the original copies may be apparent. Disclaimer The publisher has made every effort to trace copyright holders and welcomes correspondence from those they have been unable to contact. ISBN 13: 978-1-315-89670-0 (hbk) ISBN 13: 978-1-351-07580-0 (ebk) Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com PREFACE Vitamins are organic molecules that participate (directly or indi- rectly) in biological reactions in all living organisms. Organisms that cannot synthesize their own vitamins receive their vitamins through their foods or absorb some vitamins synthesized in their digestive tracts by various microorganisms. Humans depend on higher plants for most of their vitamin needs. Thus any factor that could reduce or increase the content of plant vitamins could eventually affect the vitamin intake by humans. Increasing numbers of reports indicate that some vitamins, such as vitamins A, C, and E, because of their antioxidative properties, may also play some important nonvitamin roles in living organisms by reducing the risks of some forms of cancer. This has resulted in a new surge of interest by the public and scientific community in the roles of various vitamins in our overall health and thus in the vitamin content of our food. There is a growing need to improve our knowledge of the agronomic and environmental stress factors that may alter the content of vitamins in the plant foods we consume. For example: (a) What are the natural variabilities in the content of vitamins in different varieties of the same plant? (b) Do plants vary in their vitamin content when grown in different geographical locations or in different years? (c) Does the use of chemical fertilizers, plant protection chemicals, and exposure of plants to various stress factors such as air and pollutants affect the plant vitamin contents? and (d) Are organically grown plants higher in vitamins? The aim of this book is manifold: (a) to provide a concise synthesis of the available information on the factors acting on plants during the course of their growth that affect their vitamin contents at the time of their harvest, (b) to highlight those factors that have a negative or positive effect on plant vitamins so that the proper decision can be made to alter or avoid the conditions that may reduce the plant vitamins, and finally (c) to present the available information on the effects of various stress factors on the content of plant vitamins and the roles vitamins may play in the tolerance of plants to abiotic and biotic stress factors. It is justifiable to argue that, postharvest handling and losses being equal, a plant with a relatively higher vitamin content at the time of its harvest would also contain a proportionally higher amount of vitamin when it eventually reaches the dinner table. This may especially be true for vitamins such as ascorbic acid, especially in the socioeconomic situations where proper refrigeration of food prod- ucts is not feasible. Thus any agronomic practices that could increase the content of this or other vitamins in plants at the time of their iii iv Preface harvest may have a particular relevance for improving vitamin nutrition in cases where plant foods are consumed with the minimum amount of processing and facilities for proper storage are not available. A relatively large portion of the literature on the factors affecting plant vitamins has been published in non-English (e.g., German, Rus- sian, etc.) journals and has thus gone mostly unnoticed by English- speaking scientists. It was thus decided to cite all of the literature that could be collected irrespective of "age" (a) because there is no other literature available or (b) in order to be as comprehensive as possible. Since some of the classic works on agronomic factors influencing plant vitamins are published in non-English languages, it was decided to include a sample of the data in the form of tables or graphs so future readers should not need to go to the trouble of translating the cited works, some of which have appeared in journals hard to find in most libraries around the world. I express my appreciations to the Hoffmann-La Roche of Basel (Switzerland) and the Swiss government grant for the advancement of industry (KWF) for providing assistance in my studies on the uptake of vitamins by the plant roots. I am grateful to Dr. Cyrus Abivardi for his valuable comments and encouragement during the course of writing this book. I am indebted to my family for their support and patience throughout this project. Ahmad Mozafar THE AUTHOR Ahmad (Alex) Mozafar, Ph.D., is currently docent in the Division of Agronomy, Institute of Plant Sciences, at the Swiss Federal Institute of Technology in Zurich, Switzerland. Dr. Mozafar obtained his B.S. degree in Horticulture (1964) from the University of Tehran, Iran, M.S. degree (1967) in Horticulture, and Ph.D. degree (1969) in Plant Physiology from the University of Califor- nia, Riverside. He served as assistant and associate professor at the University of Rezaiyeh (presently Urmieh), Iran, from 1965 to 1978. He served as Chairman of the College of Sciences from 1976 to 1978 at Rezaiyeh University before taking up his post as Adjunct Professor at Texas Tech University in Lubbock from 1979 to 1980. In 1991, he joined the Swiss Federal Institute of Technology. His current research inter- ests are the physicochemical and biological factors in the rhizosphere affecting the uptake of inorganic and organic compounds by the plant roots and the effects of agricultural practices on the quality and espe- cially the vitamin content of plants. Dr. Mozafar is a member of the American Society of Agronomy, Soil Science Society of America, Sigma Xi Society of America, and Swiss Society of Plant Physiology. He has authored two books in the Persian language and has authored numerous scientific papers. to my family CONTENTS 1. Nutritional Aspects ................................. 1 I. Vitamin Sources for Human Nutrition ............... 1 II. Terminology and Units .......................... 4 A Ascorbic Acid ............................. 4 B. {3-Carotene ............................... 5 C. Other Vitamins ............................ 7 III. Nonvitamin Roles ............................. 7 IV. Presence in Plants ............................. 8 V. Losses after Harvest ........................... 10 References ...................................... 13 2. Distribution of Vitamins in Different Plant Parts ........... 19 I. Leaves, Roots, and Fruits ....................... 19 II. Longitudinal Gradients ........................ 21 III. Peel Versus Flesh of Fruits; Outer Versus Inner Leaves of Vegetables . ......... 23 A Ascorbic Acid ............................ 23 B. Other