Chemical configuration and action. Paste method 



The other form is characterized by 2:3:6-trichlorobenzoic acid or the 

 corresponding aldehyde ; no other growth-promoting substance of this form 

 is yet known. We do not know if there is only one gap in the growing 

 system being filled by each of these two types of molecule, or two different 

 gaps which when occupied show the same growth effect. There is also the 

 possibility that one type of molecule is converted to the other in plant 

 metabolism. It is probable, in the latter case, that the trichlorobenzoic acid 

 would be transformed into the indole-3-acetonitrile type, for this latter 

 type includes a considerable number of chemically different substances 

 which show similarities in form but not so much in chemical behaviour. 



Figure 14. The molecular model of tetraiodofiuorescein {left) compared with that of 2:3 -.b-tri- 

 iodobenzoic acid. 



In the case of growth inhibitors, we can state that the inhibiting action of 

 fluorescein depends on its ly-like molecular form, which results when halogen 

 substitution is made as in eosine. Another type of inhibitor shows the 

 molecule form of 4:6-dinitro-o-cresol. We see, therefore, that there are also 

 two different types of molecular form consistent with growth inhibition. A 

 comparison of the forms of these two inhibitor types showed that the H'-like 

 structure of substituted fluorescein is composed of two molecules of the form 

 type of 2:3:5-substituted benzoic acid. Eosine looks like a Siamese twin, with 

 the two If^-building molecules very similar in form to 4:6-dinitro-o-cresol or 

 to 2:3:5-triiodobenzoic acid respectively {Figure 14). 



The above results show that our work has led us to some interesting 

 points of view concerning the similarities between active molecules and 

 corresponding similarities between inhibitor molecules. But it also shows 

 that much more has to be done in the future and we hope to find 

 the opportunity to study these problems further. 



REFERENCES 



Bentley, J. A. (1950). Growth regulating effect of certain organic compounds. 



Nature, 165, 449. 

 Jones, E. R. H., Henbest, H. B., Smith, C. F., and Bentley, J. A. (1952). 3-Indolyl- 



acetonitrile; a natural occurring plant growth hormone. Mature, 169, 485. 



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