Metabolism and mode of action 



attempts at identification have not been made and in the experiments 

 described above assays have been confined almost entirely to the lAA spots. 



(b) The effects qf2-A-D treatments 



Experiments on runner beans (leaf treatment), sunflowers (leaf or cotyle- 

 don treatment), and peas (applications to roots) showed no detectable 

 effects of treatments on I AA levels in the bean or sunflower shoots or in pea 

 roots and shoots. Table 1 shows the mean values obtained for a number of 

 sets of experiments. An analysis of variance of the data revealed no significant 



effect of treatment. 



Table 1 



These results are strongly opposed to the theory of Skoog and suggest also 

 that 2: 4-D has no significant effect on lAA metabolism. There seems little 

 reason therefore to doubt that 2: 4-D is an auxin in its own right and is 

 exerting its growth-modifying actions directly at the growth centres. 



2:4-D has an R^ of about 0-7 and in the chromatogram is superimposed on 

 inhibitor-^, which could not then be assayed in treated extracts. In the 

 neutral fractions of extracts from treated plants an inhibitor was found 

 giving a spot on the chromatogram at the same Rf value as 2: 4-D. It is 

 suggested that 2: 4-D in the plant forms a neutral complex with some cell 

 constituent. This complex is extracted with alcohol and is decomposed to 

 Hberate 2: 4-D during the running of the chromatogram. 



{c) The effects of maleic hydrazide treatment 



Maleic hydrazide has an R^ of about 0-2 in the solvent mixture used and 

 so both lAA and inhibitor were assayed in these experiments. Only pea 

 roots were studied. Table 2 shows the results. Levels of inhibitor (in terms of 



Table 2 



250 



