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VAN OVERBEEK 



227 



components of the smoke showed that its effect is due to unsaturated 

 hydrocarbons, principally ethylene (35). Acetylene also was found to be 

 active. These unsaturated hydrocarbons found a widespread use in the 

 pineapple industry. At present their use has declined considerably, as 

 they are being replaced by synthetic plant hormones. 



In 1939 it was discovered that naphthaleneacetic acid (NAA)* could 

 force pineapple plants into flower (10). This compound has been accepted 

 by many growers as the best of the flower-inducing agents which are 



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 80 

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MONTH OF TREATMENT 



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 MONTH OF OBSERVATION 



Figure 2. Experiment showing flower induction in pineapples of the Red 

 Spanish variety in Puerto Rico. Each month 125 plants were treated with 

 5 different concentrations of naphthaleneacetic acid (NAA), 5 cc. of which was 

 poured in the center of the plant. The amount of NAA per plant which gave 

 maximal flower induction is shown above each point of the curve; one treat- 

 ment was washed out by rain. The course of normal flowering is indicated by 

 the control curve. The results show that by the use of NAA nearly 100 per 

 cent flowering can be obtained throughout the entire year. 



*Editor's Note: In this paper as originally submitted, the abbreviations for 

 naphthaleneacetic acid and indoleacetic acid were NA and lA. For consistency, 

 these have been changed to NAA and lAA, respectively. 



