Published Physiology of Seed Deterioration

Transcription

1 Published 1986 Physiology of Seed Deterioration

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3 Physiology of Seed Deterioration Editors M. B. McDonald, Jr. and C. J. Nelson Proceedings of a symposium sponsored by Divisions C-2 and C-4 of the Crop Science Society of America in Las Vegas, NV, 28 Nov Editor-in-Chief CSSA E. S. Horner Managing Editor David M. Kral Associate Editor Sherri H. Mickelson CSSA Special Publication Number 11 Crop Science Society of America, Inc. Madison, Wisconsin, USA 1986

4 Cover Design: Julia M. Whitty Crop Science Society of America, Inc. 677 South Segoe Road, Madison, WI USA Copyright 1986 by the Crop Science Society of America, Inc. ALL RIGHTS RESERVED UNDER THE U.S. COPYRIGHT LAW OF 1978 (P.L ) Any and all use beyond the limitations of the "fair use" provision of the law require written permission from the publisher{s) and/ or the author{s); not applicable to contributions prepared by officers or employees of the U.S. Government as part of their official duties. Library of Congress Cataloging-in-Publication Data Physiology of seed deterioration. (CSSA special publication; no. 11) Includes bibliographies. 1. Seeds-Deterioration-Congresses. 2. Seeds-Physiology Congresses. I. McDonald, M. B. II. Nelson, C. J. (Curtis J.), III. Crop Science Society of America. Division C-2. IV. Crop Science Society of America. Division C-4. V. Series. SB1l8.38.P ' ISBN Printed in the United States of America

5 Table of Contents Foreword... Preface... vii ix 1 Precepts of Successful Seed Storage Eric E. Roos Membrane Changes in Seeds as Related to Germination and the Perturbations Resulting from Deterioration in Storage J. Derek Bewley Nucleotide Alterations During Seed Deterioration James D. Anderson and Kajal Gupta Nucleic Acid and Protein Metabolism During Seed Deterioration Joe H. Cherry and Ronald W. Skadsen Microorganisms and Seed Deterioration John M. Halloin Quantifying Seed Deterioration E. H. Roberts v

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7 Foreword The availability of an adequate supply of crop seeds of uniform high quality is essential for a successful seed industry and the maintenance of a viable and productive agriculture. The deterioration of seed quality of plant cultivars and germplasm is recognized as a major problem contributing to increased costs of crop production. In addition, significant losses occur due to deterioration of feed and food grains caused by seed breakage and microbial spoilage during production, storage, and handling. Continued research is needed to obtain answers on the causes of, and to provide solutions to, the seed deterioration problems. A number of symposia have been held in recent years on the mechanisms of seed deterioration. This book documents information on the physiological factors associated with seed deterioration presented at a symposium held at the 1984 annual meetings of the American Society of Agronomy and Crop Science Society of America. Physiology of Seed Deterioration will serve as a reference for researchers and educators. The society officers commend the organizing committee, the editors, and authors for their contributions. Robert F Barnes, president, 1985 Crop Science Society of America vii

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9 Preface Many facets of agriculture contribute to successful crop production. Today, the agribusiness community is composed of industries which have significant impacts on the economies of the world. These industries provide leadership for a wide spectrum of responsibilities ranging from fertilizer production, pesticide development and utilization, and equipment manufacturing to the rapidly evolving biotechnology arena. Of no less importance, and one of the major leaders responsible for the "Green Revolution", has been the development of the seed industry which began in earnest in the 1930s with the onset of hybrid seed corn production. Since that time, the seed industry, with cooperation and support from public research and educational agencies, has been responsible for providing high quality seed directly to the farmer and for the development and release of improved crop cultivars. A successful seed business is vitally concerned with seed quality control. Since the ultimate role of a seed is to reproduce a healthy, vigorous plant, seed companies and agriculturalists are interested in those factors which modify seed quality. These include the genetic constitution of the parents, as well as influences of the seed maturation environment, harvesting techniques, storage practices, and seed conditioning procedures. Any adverse treatment can result in a diminution of seed quality and an enhancement in seed deterioration. Economically, seed deterioration is a major problem in agricultural production. In the USA alone, seed sales amounted to over $2 billion in It has been estimated that 25% of that value, or approximately $500 million in revenue, was lost due to poor seed quality. Worldwide, these losses are even more staggering, particularly in lesser-developed countries and in geographic regions where high temperatures and high relative humidities prevail during periods of seed maturation and storage. Although the significance of these losses is readily apparent, the overall importance of seed deterioration becomes even more manifest when it is realized that over $800 million is lost annually due to deterioration of feed and food grains as a consequence of breakage and microorganism spoilage during production, storage, and shipping (Salunkhe et ai., 1985, p. 1-8). The gross manifestations of seed deterioration are well documented (Delouche & Baskin, 1973). These are typically exhibited as reductions in seedling growth or vigor, greater susceptibility to microorganisms, emergence of non-uniform stands, and ultimately reductions in crop yield. Despite these organismal responses to seed deterioration, it must be remembered that each physiological effect is governed by closely coordinated individual reactions at the cellular level. It has been speculated, therefore, that seed deterioration is primarily a result of deleterious alterations in cellular physiology/biochemistry, although the precise mechanisms remain to be elucidated. ix

10 The mechanism(s) of seed deterioration has been the focus of much recent experimental investigation and at least two symposia (American Society for Horticultural Science, 1980; American Phytopathological Society, 1983). It is now known, for example, that seed deterioration is a consequence of the genetic constitution of the seed, the environment during seed development, and the biochemical composition of the seed. Each of these is being actively researched at the tissue and cellular level, and progress is being made. Many studies have shown that susceptibility to seed deterioration is genetically linked and that marked differences exist between species-indeed, between cultivars-in the level and rate of seed deterioration in a given environment. Of these parameters, storage temperature and the relative humidity of the storage environment as they affect seed moisture content appear most crucial. Chapter 1 of this publication considers these effects and their interactions. Physiology of seed deterioration is no longer confined to research methodologies based on standard techniques. Since genetic and biochemical features are closely associated with the process, the entire area is amenable to molecular biology approaches to understand the pivotal reactions. Likewise, biotechnology techniques can be used to pinpoint genetic solutions to the problems. These criteria open new dimensions and point to the need for an in-depth look at the physiology/ biochemistry of the problem, especially at the cellular level. The mechanisms by which environmental conditions influence seed deterioration at the cellular level, however, remain unknown. It has been postulated that seed deterioration is a consequence of active deleterious alterations in membrane organization, nucleotide synthesis, and maintenance of DNA and protein integrity. Significant research efforts have been directed at more fully understanding these situations in deteriorating seeds and results are reported in chapters 2, 3, and 4 of this publication. Perhaps one of the most important, yet often ignored, components of seed deterioration is the influence of microorganisms on this process. Seed deterioration and microorganism invasion are often associated, but the relative role of microorganisms as the cause or consequence of seed deterioration remains unresolved. This issue is comprehensively addressed in chapter 5. Finally, a consideration of seed deterioration clearly indicates that many independent physiological and environmental factors interact to influence this process. In some cases, these factors may act synergistically while in others, they may be additive. Chapter 6 integrates these parameters into a predictive model which quantifies seed deterioration under given environmental conditions. This special publication, Physiology of Seed Deterioration, is a product of a symposium presented at the 1984 annual meetings of the American Society of Agronomy Meetings in Las Vegas, NV. The symposium was sponsored jointly by Div. C-4, Seed Physiology, Production, and Technology, and Div. C-2, Crop Physiology and Metabolism. As Ofx

11 ganizers of the symposium and editors for this publication, we wish to acknowledge the excellent assistance, cooperation, and suggestions provided by the authors, and the support of the membership from the respective divisions. REFERENCES American Phytopathological Society Deterioration mechanisms in seeds. Phytopathology 73: American Society for Horticultural Science Seed quality: An overview of its relationship to horticulturists and physiologists. Hortic. Sci. 15: Delouche, J.C., and C.C. Baskin Accelerated aging techniques for predicting the relative storability of seed lots. Seed Sci. Techno!. 1: Salunkhe, O.K., J.K. Chavan, and S.S. Kadam Postharvest biotechnology of cereals. CRC Press, Boca Raton, FL. Miller B. McDonald, Jr., C-4 chair, Curtis J. Nelson, C-2 chair, xi