82 PLANT GROWTH SUBSTANCES 



However, no man's word is law; all claims must be tested and proven 

 before they are acceptable in science. 



Interest in the subject of plant hormones from the standpoint of 

 fundamental science is still uppermost in the minds of many workers. 

 It is increasingly evident, however, that an attack on practical problems 

 in the field of plant hormones also contributes to fundamental science. 

 It may be said that when practical problems are properly studied, the 

 results of the investigation contribute to both science and practice. 

 Laboratory curiosities pointed the way to horticultural applications. 

 To show the wide interest in the field of plant hormones, the following 

 titles of publications which recently came to my desk are taken at 

 random: 



Inducing fruit set and seedless tomatoes 

 Hormones retard bud development 



Hormone sprays and their effect upon the shipping and keep- 

 ing quahty of Bartlett pears 



Effects of certain growth-regulating compounds on Irish 

 potatoes 



Inhibition of bacterial growth by auxins 

 Apple-bloom thinning with chemicals 

 2,4-D hits cotton again 

 New weed killer plant for Australia 



Direct introduction of chemical substances into herbaceous 

 plants 



2,4-D injury to trees 



Spraying is a new method of applying root-promoting sub- 

 stances 



The use of 2,4-D in rice fields for the control of weeds 

 Quack grass conquered by new chemical powder 

 Method of defoliating 



The enzymatic inactivation of indoleacetic acid 

 Synthetic plant hormones and the pineapple industry 

 Foresee new uses for 2,4-D 



The groups of chemicals best known as growth regulators are as 

 follows: Indole compounds involving ,S-indoleacetic and /3-indolebutyric 

 acids; naphthalene compounds involving a-naphthaleneacetic acid and 

 its derivatives, /3-naphthoxyacetic and j8-naphthoxypropionic acids and 



