Growth-Regulating Substances in Relation to 

 Reproduction of Some Horticultural Plants 



A. E. MURNEEK 



DURING the past third of a century I have been interested in the 

 physiological aspects of sexual reproduction of the higher plants, 

 and for about a quarter of a century my major research project has 

 been, and still is, on the "Physiology and Reproduction of Horticultural 

 Plants." In this activity quite naturally I have been led recently into 

 studies of certain theoretical aspects of the function of plant hormones 

 and the practical application of so-called synthetic growth regulators 

 with special reference to the production of horticultural crops. 



The physiology of sexual reproduction has been till recently, a much 

 neglected field of investigation, as one may judge from inspection of any 

 textbook of plant physiology. The relatively recent discoveries of the 

 striking effects of the photoperiod and temperature, however, have 

 created much interest in this phase of the functional hfe of plants (93,62). 

 Now the naturally occurring auxins and even more the synthetic growth 

 regulators have come under consideration in flower and fruit develop- 

 ment. 



Personally, I dislike the widespread use of the term auxin whose 

 original meaning was that of a catalytic substance (hormone) bringing 

 about growth by cell elongation. Recently it has been used to designate 

 not merely one of the three originally discovered auxins, heteroauxin, 

 but practically all synthetic growth regulators employed in experimental 

 work (68). Surely there are many more native hormones in plants than 

 indoleacetic acid. One cannot conceive that as vital and complicated 

 a process as the formation and development of flowers, seeds, and fruit, 

 with their diverse structures and manifold physiological functions. 



