230 PLANT GROWTH SUBSTANCES 



slip production as a result of NAA treatment. It is entirely possible that 

 among the auxins a compound, or combination of compounds, may be 

 found which does cause flower initiation, and yet does not suppress the 

 lateral bud development. 



Crop control in the pineapple is not complete without a means 

 whereby it is possible to prevent precocious flowering. This has been 

 accomplished by the application of large quantities of auxins. Theo- 

 retically this is understandable as it seems to be a general rule that 

 auxins stimulate at low concentrations, while they inhibit these same 

 reactions at high concentrations (27). From a practical standpoint this 

 principle has not worked out satisfactorily for the control of undesired 

 flowering in the pineapple. It is not impossible that growth inhibitors 

 such as maleic hydrazide (36) might supply the solution to this problem. 



As a result of the rapid progress in chemical growth regulation our 

 fundamental concepts of which characteristics in a plant are desirable 

 and which are not must undergo considerable change. Prior to chemical 

 growth regulation it was desirable for a plant to flower readily during the 

 natural flowering season, as this insured a high average annual yield per 

 acre. At present, with cheap and efficient chemical growth regulation 

 at our disposal, we would prefer plants which would not flower at all, 

 except after chemical treatment. This would do away with the problem 

 of precocious flowering, making planting throughout the entire year 

 possible, thereby permitting fruit production on a commercial scale 

 throughout the entire year. The Cabezona variety of Puerto Rico 

 approaches these qualifications. It produces flowers readily after treat- 

 ment with minute quantities of synthetic auxins, yet does not flower 

 abundantly in the natural season (48). 



Physiology of Jlower formation in the pineapple. — The pineapple is the 

 only plant in which the application of known compounds will cause 

 flower formation. Since, with the exception of ethylene and acetylene, 

 these compounds belong to the group of the auxins, a study of the 

 physiology of flowering is of more than local interest. Auxins are not 

 species specific, and experience has taught that when an auxin elicits a 

 certain reaction in one plant species it is likely to do likewise in most 

 other species. Thus, when auxin causes pineapples to flower, it is most 

 likely that in other plant species also it is involved in the process of 

 flowering. 



