76 Fawcett, Wain, and Wightman 



mined in each experiment. The results obtained are recorded in his- 

 togram form which shows clearly the position on each chromatogram 

 of compounds with growth-promoting activity. 



EXPERIMENTAL RESULTS AND DISCUSSION 



The activity shown by members of the series of acids, amides, ni- 

 triles, and methyl esters in the wheat and pea tests are shown in 

 Table 2. For convenience, the results for each series will be discussed 

 below in separate sections together with the evidence obtained in chro- 

 matographic studies on the metabolism of these compounds in wheat 

 and pea tissues. 



Chromatographic analysis of the extracts of solutions of all the 

 compounds incubated for 48 hrs. at 25° C. in the absence of tissue 

 showed that with the exception of certain methyl esters, all were ef- 

 fectively stable under these conditions. In the case of the ester series, 

 indications were obtained to show that several of these compounds 

 will hydrolyze to a slight extent to the corresponding carboxylic acid 

 when solutions are left in an incubator for 48 hrs. The production 

 of the corresponding carboxylic acid in untreated solutions, however, 

 was in no way comparable with the amount produced when the solu- 

 tions were exposed to wheat or pea tissues. 



a)-(Indole-3-)alkanecarboxylic Acids 



With the exception of indole-3-carboxylic acid, all members of 

 this series are highly active in the wheat cylinder, pea segment, and 

 pea curvature tests (Table 2) . The acetic, butyric, and caproic homo- 

 logues are the most active members of the series, and this result 

 is consistent with the probable degradation of the side-chain of the 

 latter two acids by j3-oxidation to yield the highly active acetic deriva- 

 tive. The activity shown by the propionic, valeric, and heptanoic 

 derivatives appears, at first, to be inexplicable in terms of (3-oxidation 

 of the side-chain within the test tissues since the expected end-product, 

 namely indole-3-carboxylic acid, has no growth-promoting activity. 



When solutions of all these acids were exposed to wheat coleop- 

 tile or pea stem tissues, the chromatograms obtained using extracts 

 of the residual tissues and solutions provided clear evidence that (3- 

 oxidation of the side-chain of the higher homologues had occurred 

 ill Ijoth tissues employed (Figure 1). Thus both chromatograms 

 showed evidence of a blue spot corresponding to the acetic acid in 

 extracts from treated butyric and caproic acid solutions, and further- 

 more, the caproic derivative also yielded the butyric acid presum- 

 ably as an intermediate degradation product. Similarly, a blue spot 

 corresponding to the propionic acid was obtained in both tissues from 

 the valeric and heptanoic acids, the latter acid also producing the 



