CHAPTER 2 



Life Span of Seeds 



How long do seeds live? This is a very complex question to answer, for 

 there are many species of seeds varying greatly from one to the other in 

 life span under any one condition of storage. ^^ The condition of storage 

 modifies the life span of seeds tremendously. A given storage condition may 

 lengthen the life span of one species and shorten that of another. 



In his well known and excellent book, "On the Longevity of Seeds," 

 published in 1908, Alfred J. Ewart^^ gives a rather pessimistic view of the 

 accuracy of the knowledge in this field. He says: ''Probably few sections 

 of human knowledge contain a larger percentage of contradictory, incor- 

 rect and misleading observations than prevail in the works dealing Avith 

 this subject, and, although such fables as the supposed germination of 

 mummy wheat have long since been exploded, equally erroneous records are 

 still current in botanical physiology. In addition, there are considerable dif- 

 ferences of opinion as to the causes which determine the longevity of seeds 

 in the soil or air. The works of de Candolle, Duvel, and Becquerel are the 

 most accurate and comprehensive dealing -with the question, and, in addi- 

 tion, Vilmorin has published very useful data in regard to the seeds of culi- 

 nary vegetables. The subject is still, however, in an incomplete and fragmen- 

 tary condition." 



Since Ewart's classic work was written, many new data and much evi- 

 dence have been accumulated in this field, and definite advances have been 

 made in several phases of the subject, including the nature of the changes 

 involved in the degeneration of seeds with age and the effect of storage con- 

 ditions on their rate of degeneration. Many new records have appeared on 

 life span of seeds of mid plants in herbaria and seed cupboards and of seeds 

 of cultivated plants in storage. We also now have available a good deal of 

 reliable data on the life span of seeds in soil. 



On the basis of their life span under optimum conditions, Ewart divides 

 seeds into three biological classes: (a) microbiotic, whose life span does not 

 exceed 3 years; (b) mesobiotic, whose life span ranges from 3 to 15 years; 

 and (c) macrobiotic, whose life duration ranges from 15 to more than 100 

 years. As we shall see later, we do not have final information on the opti- 

 mum storage conditions of many kinds of seeds, and in spite of the great 

 amount of research that has been done on seed storage in recent years it is 

 questionable whether anyone can give optimum conditions for the storage 

 of any sort of seed, although one can give good conditions that will greatly 



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