Plant Hormones in Practice 



p. W. ZIMMERMAN 



AS A concept lying along the frontiers of science, plant hormones 

 appeared on the horizon with the pubhcation in 1880 by Charles 

 Darwin of a book called The Power of Movement in Plants. Startling 

 advances have been made and in a way each new phase of the subject 

 has constituted a new horizon. 



My assignment today concerns a chemical revolution in science and 

 horticultural practice; that is chemical regulation of the pattern of 

 growth and development of plants. The subject is new but the progress 

 has been rapid. The chemicals involved are called hormones, auxins, 

 or growth-regulating substances. The early experiments and results were 

 looked upon as laboratory curiosities, but they finally led to botanical, 

 agricultural, and horticultural apphcations which are sweeping the world 

 today. Owing to the varied types of responses induced by plant hor- 

 mones, the subject drew the attention of botanists, horticulturists, and 

 chemists. Professors in universities found the field a fertile one for 

 graduate students and assigned projects which resulted in published 

 theses for advanced degrees. Publications are now pouring out at a 



rapid rate. 



No one person or small group of persons could ever have discovered 

 all the facts that are now known about plant hormones. It is hardly 

 conceivable that extensive horticultural applications could have arisen 

 from the simple but profound researches involving the bending of the 

 oat coleoptile exposed to unilateral illumination and the realization 

 that this was due to an influence of a chemical nature. It was by no means 

 easy for scientists to agree on the meaning of such growth responses, 

 but through fear, envy, suspicion, interest, and curiosity one worker 

 picks up where another leaves off and advances our sphere of knowledge. 



