(2-Chloroethyl)tri7nethylammoniiim Chloride 785 



is not structurally related to (2-chloroethyl)trimethylammonium chlo- 

 ride except that both are quaternary ammonium salts. Both com- 

 pounds promote short stem growth, and in both cases these changes 

 are reversed with gibberellin. AMO 1618 was not active on wheat, 

 but on the other hand (2-chloroethyl)trimethylammonium chloride 

 was not very active on chrysanthemums. Thymohydroquinone and 

 thymoquinone have been reported to induce wheat to grow with a 

 shorter stem (2). The structure of thymohydroquinone 2-isopropyl- 

 5-methylammonium chloride is also not related to chlorocholine 

 chloride. Thymohydroquinone in our tests on wheat was toxic at 

 \0'"M, caused dwarfing at lO'^M, and induced little effect at \Q'*M. 



Mode of Action 



The effect of the (2-chloroethyl)trimethylammonium chloride de- 

 rivatives as chemicals to induce growth of plants with shorter and 

 thicker stems seems characteristic of a new type of plant growth sub- 

 stance. There is so far no evidence that these chemicals are naturally 

 occurring nor any evidence as to their mode of action. They are not 

 particularly toxic to either plant or animal. Since a minute amount 

 of the chemicals, when applied once to young plants, affected the 

 further growth and development of the plant during an entire grow- 

 ing season, it is likely that the compounds were not rapidly metabo- 

 lized or bound into a part of the cell structure. The high degree in 

 specificity of structure for biological activity suggests that they may 

 affect an equally specific enzyme site. This can be postulated as a 

 protein with one binding site for the trimethylamine end of the mole- 

 cule and one site for the chloro, bromo, or r^CHo group. The two 

 active sites must be about the length of the ethyl, carbon chain apart. 



(2-Chloroethyl)trimethylammonium chloride is structurally related 

 to choline and betaine in that the number 2 carbon of the ethyl chain 

 is halogenated instead of being an alcohol or acid group. From this 

 similarity it may be postulated that these derivatives may be influenc- 

 ing lipid metabolism or transmethylation reactions. Alteration of 

 either of these processes might cause altered cell development which 

 would result in shorter plant growth as has been observed. 



SUMMARY 



Compounds of the structure (CH3)3N+CH2-CH2X are active as 

 plant growth substances when X is CI, Br, or r=CHo group. Solutions 

 of (2-chloroethyl)trimethylammonium chloride, (2-bromoethyl)tri- 

 methylammonium bromide, and (2,3-n-propylene)trimethylammonium 

 bromide were active at IQ-^M when poured on the soil. Treated 

 wheat plants grew with shorter and thicker stems and greener leaves 



