784 N. E. Tolbert 



This phenomenon, however, becomes a problem in reproducing 

 the results. All of our first experiments were carried out in the green- 

 house in the winter when the available daylight intensity was low. 

 Later, when the experiments were redone in April and May, the 

 percentage decrease in stem length from the chemical treatments was 

 less. The effects of the chemical had not changed markedly, but the 

 length of the stems of the control plants was less since the plants were 

 then growing in high light intensity. However, the general pattern 

 of shorter and bushier growth after treatment with (2-chloroethyl)tri- 

 methylammonium chloride was still obtained during the summer 

 months. 



Effect of Temperature 



The (2-chloroethyl)trimethylammonium chloride derivatives were 

 most effective at lower temperatures. This was true for the growth 

 of wheat which was tested at temperatures of 56° F. night and 70° F. 

 day, 65° F. night and 75° F. day, and 80° F. night and 85° F. day. 

 Also, wuth tomatoes in the greenhouse the effects were more pro- 

 nounced under relatively cool (55 to 60° F.) temperatures and during 

 the short days of fall and winter. Favorable responses have, however, 

 resulted for both plants at higher temperatures as well as for the 

 other plants so far tested. Thus, although the compounds are most 

 effective near the optimum growth temperature, they may be val- 

 uable when applied to plants at temperatures where satisfactory 

 growth is not readily obtained. 



(2,3-n-Propylene) trimethylammonium Bromide 



Only recently has it been realized that the propylene derivative 

 ^\as active. At this time it appears to be the most promising com- 

 pound, since growth of sturdy plants with broad and green leaves 

 without as great a reduction in over-all height of the plant was ob- 

 tained when it was applied over a range of lO-^M to less than IQ-^M. 

 Further, this (()m[)ound on tomato plants appears to be very effective 

 at the elevated temperatures and light intensities obtained in the 

 summer (6). 



Similarity of Action to Other Chemicals 



Several other chemicals have been reported to cause plants to 

 grow with shorter stems when applied to plants in low concentra- 

 tions, and it was of interest to compare their structure and activity 

 with the (2-chloroethyl)trimcthylammoniiun chloride derivatives. 

 AMO 1618, 2-is()propyl-4-dimethylamino-5-methylphenyl-l-piperidine 

 carboxylate methykhloride has been reported to promote shorter 

 stem growlli of chrysanthemums and other plants (1, 3). AMO 1618 



