Chemical structure and biological activity 



1/100 of that of indole-3-acetic acid. Weaver (1952; 1954) observed that 

 benzothiazol-2-oxyacetic acid applied to grape plants at flowering resulted 

 in a high percentage set of rather small fruits. We tested this substance with 



Figure 4. The concentration-action 

 curves of 2-oxybenzthiazoleacetic acid 

 (BTOES) and indole-'i-acetic acid 



{lAA). 



10-" 10" 



log con en. 



the paste test and found slight growth-promoting activity, about 1/100 that 

 of indole-3-acetic acid {Figure 4). In all, we have tested about one hundred 

 different synthetic substances which seemed to be of some interest in 

 comparing the form of the molecule with its activity. 



Figure 5. The concentration-action 

 curves of 3-arnino-triazole (3 AT), 

 imidazole-4-acetic acid (Im-4-£), and 

 indole-'i-acetic acid {lAA). 





+ (?^ 



*eo 



9^ 



*¥0 



% 



:S ^20 





I 



5 



-20 



lAA 



10 



-w 



--2 



10-'- 10" 



log concn. 



In further experiments we found 3-aminotriazole to possess a very small 

 activity not more than 1/1000 of indole-3-acetic acid {Figured). iViV-phenyl- 

 methylglycine ethyl ester showed a good activity as a growth promoter, 

 whereas that of 2-methylbenzimidazole and 2:4-dichlorophenoxyacetic 

 acid-bisoxyethylamide was slight. In this group of 2:4-D derivatives, in 



144 



