Metabolism and mode of action 



was not detected by Stowe and Thimann (1954) during their chromato- 

 graphic study of the breakdown of IAN by oat tissue. The results from the 

 present investigation show that pea and tomato tissues are unable to hydrolyse 

 IAN to lAA, though they can convert the amide to the acid. Wheat tissue, 

 on the other hand, is able to hydrolyse the nitrile to the acid, but apparently 

 can only effect slight conversion of the amide to the acid {Figures 3 and 4). 

 This evidence, coupled with the complete absence of any chromogenic 

 indication of lAAm formation during the hydrolysis by IAN by wheat 

 tissue, strongly indicates that free amide is not an intermediate in the 

 hydrolysis of IAN in plant tissues. 



The slight hydrolysis of the nitrile and ready conversion of the amide to 

 lAA by maize tissue when compared with the effects of wheat tissue on these 

 two compounds, suggests interesting differences in the enzymatic make-up of 

 these closely related species. On the other hand, celery tissue which effects 

 only slight hydrolysis of both amide and nitrile, appears to differ from all 

 other tissues examined. All the tissues under discussion, however, appear to 

 have one property in common, they are all capable of readily converting 

 lAMe to lAA. 



One of the most interesting observations recorded in this work is the 

 appearance of a substance during the metabolism of IAN by wheat tissue 

 which behaves on the chromatogram like indole-3-carboxylic acid. The 

 identification of this substance, which is also produced, though to a lesser 

 extent, when IAN is treated with the other tissues employed, has received 

 further study. Since treatment with wheat tissue appears to effect the 

 best conversion of IAN to this compound, extracts of nitrile solutions 

 treated in this manner have been used to confirm its identity with 

 indole-3-carboxylic acid. 



It was shown, by chromogenic estimation, that the amount of this substance 

 formed by a given amount of wheat tissue (50 X 1 cm coleoptile segments) 

 markedly increased when the supply of IAN in the test solutions (50 ml) was 

 increased (i.e. the amount formed was proportional to the concentration of 

 IAN up to 4 mg/1.). Similarly, the compound was never formed from IAN 

 in the absence of living tissue, maximum conversion being achieved with 

 50 coleoptile segments per 200 jig IAN. 



When an extract of wheat-treated IAN was run in two different solvents 

 (butanol:ammonia:water, and f^opropanol: ammonia: water) and using two 

 different types of chromatographic paper (Whatman No. 1 and 'Devon 

 Valley' 431 Mill blotting paper) the compound always moved the same 

 distance as authentic indole-3-carboxylic acid. Since blotting paper permits 

 a fairly rapid movement of the solvent a wider separation of lAA and 

 suspected ICA could be achieved by allowing the solvent front to flow off 

 the paper. Using this technique, it has been possible to separate and 

 extract ca. 0-1 mg of the suspected ICA from large volumes of wheat-treated 

 IAN solutions. This extract was submitted to Professor E. A. Braude 

 (Imperial College, London) for ultra-violet spectrographic analysis, the 

 results of which strongly suggest its identity with indole-3-carboxylic acid. 

 In a later experiment, the infra-red absorption spectrum was shown by 

 Mr. J. G. Reynolds (Woodstock Research Station, Sittingbourne) to be 

 identical with that of ICA. Finally, the />-phenylphenacyl ester of the acid 



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