Metallic Ions, Auxin Action, and Chelating Agents 369 



of Avena first internodes were used, since these have been found 

 more responsive to very low auxin concentrations (15, 18). However, 

 to our surprise, first internode sections showed no marked response, 

 either to EDTA or 8-HOQ, over the whole range of concentrations 

 up to lO-^M. They showed excellent response to lAA, however, at 

 a concentration which showed only a small growth promotion in 

 coleoptiles. 



I- 

 < 

 (3 



O 



_J 

 Ixl 



120 



no 



100 



T 



T 



T 



Su 2% 

 + EDTA 



.001 .01 0.1 1.0 10 



CONCN. OF lAA (MG/L) 



Fig. 3. Effect of EDTA on promoting the elongation of coleoptile sections, as 

 a function of lAA concentration and presence of sucrose (Su). All experiments 

 in O.OIM phosphate, pH 5.5. 



