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 Essay - may/june 2005
Thoughts and reflection seed storage
James C. Delouche
Professor Emeritus Mississippi State University
Seed longevity and dormancy were among my first and, perhaps, most lasting interests in seed biology. I "discovered" these fascinating aspects of seeds in the many publications of Barton and Crocker during my first year (l950-51) of graduate studies in Botany at Iowa State University. William Crocker, Director of the Boyce Institute for Plant Research, Yonkers, N.Y., a privately endowed institute now under Cornell University, and Lela Barton a senior scientist of the Institute, were the foremost seed biologists and technologists of their times (circa 1920-1965). While my early interests in seed longevity and dormancy were mostly academic, ironically, Crocker and Barton's researches on seeds were more applied than basic. They worked out the very complex mechanisms of dormancy in seeds of temperate climate trees and shrubs, developed means of assessing their viability, efficient and effective procedures for commercial scale storage of the seeds and production of seedlings and young plants by nurseries and arboretums. And, they were among the first to investigate the biological potential and economic feasibility of climate control technology for the long-term storage of seeds. Much of their work and ideas was summarized in the first modern references on seeds published in the USA: Physiology of Seeds, Wm. Crocker and L. Barton, 1953, and Seed Preservation and Longevity, L. Barton, 1961.
My academic interest in seed longevity changed rather quickly to an applied, problem-solving interest in seed storage when I joined the Seed Technology group at Mississippi State University in 1957. Seed producers and companies were experiencing substantial and "unexpected" decreases in germination of seed lots during storage and were urgently seeking technical assistance to reduce their losses of seeds and profits. Many of them turned to the seed technology group at MSU that was then emerging as the principal seed technology center in the country. I recall that we were literally besieged with requests and personal visits from seed producers and companies seeking advice, information and technical assistance on ways to eliminate or at least minimize seed storage losses. Many of the seed producers and companies seeking assistance began by described in detail the physical facilities, i.e., storerooms, used for storing seeds, or showing them to us during visits because in their view that was the site of their problems. This view was not surprising. Seed lots determined to be low in germination before or after processing were usually diverted to non-seed uses or discarded, and would not have been packaged and placed in the seed storeroom. Packaged seed lots placed in storage, therefore, had acceptable germination and were expected to maintain it through the marketing process. Since germination was good when the seeds were placed in the storeroom, most decreases in germination to unacceptable levels determined or detected anytime thereafter were attributed to something that occurred in the storeroom or during distribution and marketing.
After a year or so of visits with and to seed producers and companies, inspections of their facilities, reviews of many sampling and testing records, making a lot of inspections and tests ourselves, and considerable thinking we realized that many, perhaps most, of the germination loss problems detected in the storeroom or in distribution channels originated during operations that preceded packaging. We began to recognize and appreciate the many factors, economic, technical, biological, and professional, involved in what were being called "seed storage problems." Agriculture had begun to change rapidly and profoundly in many developed and developing countries after World War II, especially beginning in the 1950s. In the USA crop agriculture was becoming much more mechanized, technical, diversified and market-oriented. Planting and harvesting of most crops were essentially fully mechanized. Soybean was becoming a major crop, hybrid varieties of maize were dominant and sorghum hybrids were becoming available. Special government problems were increasing the planting of forage and conservation crops, and the agribusiness sector was rapidly expanding to supply farmers with the technical inputs they needed such as fertilizer, herbicides, pesticides and seeds.
Many kinds and varieties of seeds in large quantities were being produced by an increasing number of producers and companies, some of them new to the seed business and most of them dependent on contract seed producers. Inexperience and insufficient knowledge and expertise, i.e., inadequate professionalism, on the part of both seed companies and contract seed producers turned out to be the major factor in most of the quality problems labeled "seed storage problems." As a result of inexperience, lack of knowledge, inadequate technical expertise and supervision of operations, seeds were subjected to a variety of physical and physiological traumas. In some cases the traumas were so severe that their effects were obvious, germination was immediately reduced and the seeds were rejected for seed use. In many other cases, however, the effects of the traumas were not noticeable and immediate but subtle and latent. They initiated deteriorative processes that did not affect germination until much later, until the seeds were in the storeroom or distribution and marketing channels.
Seeds were subjected to many sorts and degrees of traumas. Unnecessary delays in harvesting exposed seeds to climatic conditions in the field that were sometimes very unfavorable for maintenance of germination and vigor, e.g., rain, warm temperatures, high humidity. Improper and inexpert management of mechanical harvested operations subjected seeds to high incidences of mechanical abuse of varying severity. Aeration and drying facilities needed to reduce high moisture content seeds to levels safe for handling and processing were frequently not available, aeration or drying operations were sometimes unnecessarily delayed or they were technically inadequate. Seeds of soybean were physically more delicate and physiologically shorter-lived than those of the older crops such as maize, wheat, and sorghum with which producers had much more experience. High quality soybean seeds were difficult to produce, handle and store in most areas but especially in warm, humid climates. Acid delinting technologies used to improve the flowability of cotton seeds for processing and planting caused heat and acid burn damage to the seeds when the processes were not properly controlled, especially on seeds that were damaged during mechanical harvesting and ginning. Even the newly available moisture vapor resistant plastic packages marketed for safer seed storage turned out to be very unsafe when seed moisture content was not reduced to the relatively low levels needed for safe seed stored of seeds.
When the MSU seed technology group became involved in technical assistance to developing countries in the late 1950s, they soon encountered "seed storage problems" that were much more common, severe, complex and limiting than in the USA and other countries with temperate climates. The rapid deterioration of seeds in the humid tropics and sub-tropics was and still is a major impediment to use of improved seeds for development of crop agriculture. Much of the development assistance on seed program development to the tropical and subtropical countries during the 1960s and 1970s had to be focused on producing seeds of acceptable quality under warm, wet and humid conditions.
The seed storage problems in the USA, other countries with temperate climates and in the humid tropics and subtropics were reduced to manageable levels by the proven methods used for resolving and/or managing all sorts of problems: training and education, problem solving research, professionalism of supervisors and key technicians, adaptation, development, and adoption of effective and efficient technologies, and informed, responsive and responsible management. In the seed production and supply sector these problem solving methods have evolved into the quality assurance and control systems that presently undergird all operations in progressive seed companies.
I am pleased and very satisfied to have been a member of the MSU seed technology group that contributed in so many ways during the last half of the last century to improvements in the quality of seeds supplied to farmers in the USA and in many other countries throughout the world. Reflecting on these times I realize how very fortunate I was in choosing seed longevity and dormancy for my first, foremost and longest interests in seed biology for they led to the development of concepts and technologies that contributed significantly to improvements in seed quality and performance. These and related contributions of others will be the subject of additional thoughts and reflections on seed longevity, storage and dormancy in the next several essays.
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