80 



Fundamentals of Auxin Action 



growth test led to the eventual finding that it probably has its effects 

 on growth partly through its conversion to the free acid and partly 

 through its synergistic action in the presence of acid auxins (Osborne, 



6 - 



4 - 



X 



0.1 



10 



10 M6/L 



CONC OF I Ac 



ORIGINAL CONC OF lAc 



Fig. 39. The effect of indoleacetaldehyde on growth in the Avena straight-growth 

 test. A, growth responses to indoleacetaldehyde; B, the growth responses to the 

 acidic and to the neutral fractions taken from the solutions after completion of A 

 (Bentley and Housley, 1952). 



1952). The most likely pathway for the conversion of the nitrile to 

 indoleacetic acid would be through the oxidation to the acetamide 

 as an intermediate compound: 



CH,CN 



H2O 



N 

 H 



indoleacetonitrile 



MOVEMENT 



CH,C 



NH, 



H,0 



CHgCOOH ^ NH3* 



indoleacetic acid 



indoleacetamide 



Early work on the movement of auxins in the Avena coleoptile 

 demonstrated that no particular type of tissue was exclusively involved 



