306 Auxins in Agriculture 



auxin today is that so much is known about the gross effects of auxins 

 and so little is known concerning the mechanism underlying these 

 actions. Surely a knowledge of the means by which auxins act at the 

 metabolic level will have immense implications in the intelligent ap- 

 plication of auxins in the technology as we know it today. Further it 

 seems very likely that a knowledge of the mechanism of auxin action 

 will open up new possibilities for auxin applications which have re- 

 mained undiscovered to date. All these considerations make it par- 

 ticularly remarkable that more attention has not been given toward 

 improving our fundamental understanding of the mechanism of 

 auxin action. 



WHAT CAN AUXINS DO FOR AGRICULTURE? 



Examination of the uses of auxins in agriculture indicates tli 

 auxins present the agriculturist with three types of tools. 



The first tool is the ability of auxins to overcome certain limita- 

 tions of growth and development imposed by brief insufficiencies of 

 the environment. The most obvious examples of this type of usefulness 

 of auxin are in the control of fruit-set and of fruit drop. When 

 weather conditions are unfit for normal pollination and setting in the 

 tomato, the application of auxins can initiate the growth phase 

 which would normally take place at the time. Likewise if weather 

 conditions at the end of the summer are such as to encourage prema- 

 ture drop of apple fruits, the application of auxins can retain fruits 

 on the trees until harvest. 



The second tool which auxins supply is a control of the type of 

 growth which will take place. The simplest example of this type of 

 usefulness is in the rooting of cuttings where the capacity to grow is 

 inherent in the cutting, but this capacity needs to be directed toward 

 the development of roots to attain the goal of successful propagation. 



The third tool which auxins present is the property of facilitating 

 the mechanization of agriculture. This is perhaps the most importan' 

 tool of all in that it is the basis for the greatest use of auxin, the her- 

 bicidal use, and it makes possible the most widespread economic gains. 

 The thinning of flowers and fruits is another instance where an auxin 

 spray is substituted for manual labor. The chemical control of flower 

 initiation in pineapple is another good example of auxins facilitating 

 mechanization — in this case the mechanization of harvesting. 



While these three tools may be very useful under certain circum- 

 stances, it is quite clear that two major reservations should be kept in 

 mind concerning their usefulness. In the first place the agricultural 

 uses of auxins are liable to create new^ agricultural problems of their 



