GEORGE L. McNEW 



Boyce Thompson Institute 



The Broader Concepts of Plant 



Growth Regulation 



Men and plants have come a long way together down through the 

 ages. The association has long since changed from the casual contact 

 of a nomad with a quick meal to that of almost complete interde- 

 pendence. One of the major goals of civilization has always been to 

 improve the usefulness and reliability of plants in promoting human 

 welfare. Those societies that have failed to achieve this improvement 

 in proportion to the material needs of a growing population have 

 crumbled and perished from the earth. 



THE PLASTICITY OF THE GROWING PLANT 



The plant scientist of the twentieth century has come to look 

 upon the major crop plants as so many plastic materials of life that 

 can be shaped and altered by skilled hands. Much of the altered 

 design of plant development has been achieved by genetics — first by 

 studying natural variants and selecting the preferred races and varie- 

 ties, and more lately by selection of suitable building blocks for syn- 

 thesizing new varieties with highly specialized attributes. 



This synthetic process of hastening or diverting the ordinary pro- 

 cesses of evolution has come to be considered entirely inadequate. 

 The natural processes of inherited growth regulation fail in so many 

 respects that the geneticist has sought new tools such as gene muta- 

 tion by irradiation or induction of polyploidy by chemicals or other 

 means. The heritable processes of plant regulation are very desirable 

 in that they are spontaneously self-reproducible and hence very eco- 

 nomical to use once they are properly established. 



As men have gradually unravelled the mysteries surrounding nor- 

 mal metabolism and growth processes in plants it has become clear 

 that nearly all regulatory processes depend upon underlying chemical 



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