CHAPTER I 



Development of Knowledge 

 of Auxins 



The development of the knowledge of auxins, as in the case of nearly 

 all major scientific advances, originated in experimental inquiries by 

 scientists seeking answers to fundamental questions. If any one worker 

 could be identified as first in the field, perhaps it would be Charles 

 Darwin, who in 1881 published his book The Power of Movement in 

 Plants. His investigations of fundamental questions about plant tro- 

 pisms opened a minute gate in the dike of the unknown which ulti- 

 mately led to the flood of information concerning not only tropisms, 

 but the whole general field of plant growth and the growth hormone 

 as well. In the seventy years following this modest beginning, the role 

 of the growth hormone in plants has been clarified to an almost star- 

 tling degree. The revealed capacity of many chemical compounds to 

 exploit the same mechanisms in plants has led to a situation nearly 

 approaching an agricultural revolution. Auxins and growth regulators 

 promise to have an impact on agriculture as great as the advent of the 

 windmill or perhaps even of the mechanical harvester. At the same 

 time the impact on the science of plant physiology is as great as that 

 of any other single development since the turn of the century. 



DEFINITIONS 



There has been a considerable confusion among physiologists and 

 agriculturists concerning the terminology of auxins and growth hor- 

 mones. Before entering into an extensive discussion of these com- 

 pounds, it will be well to define our terms. 



A hormone has been accepted for many years as being "a sub- 

 stance which, produced in any one part of an organism, is transferred 

 to another part and there influences a specific physiological process" 

 (Went and Thimann, 1937, p. 3). It may be advisable to emphasize 

 that hormones are produced in the organism, and have the property 

 of serving as chemical messengers, i.e., they are transported from a site 

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