Investigation of natural auxins and growth inhibitors 



markedly increases the response of oat coleoptile sections to lAA, though 

 Schneider (1941) reported that first internodes were almost insensitive to 

 sucrose. A study of this point, conducted with both coleoptiles and internodes, 

 demonstrated beyond any doubt that the growth of first internodes as well as 

 that of coleoptiles is strongly increased by sucrose in the presence of lAA and 

 that the optimum sucrose concentration is 2 per cent {Figure 14). 



w 



3-0- 



"1 2-0 



1-n 



I 2-5 

 Z-0 

 I 

 t^ 1-0 



(a) 



/ \lAA50yl\ 



y 



/ ~° 





Con. \ 



Avena coleoptile 



I I I I I I L 



_a 



(t) 



/7l I I I I I I 



I I I 



(c) 



IAA30y/\ 





o o^ Con. 



° Sorghum first intern ode 



II I I \ \ I L 



Cd) 



II I I 



^- 



s 



Con.\> 



Avena f/nst internode 



\\ I I \ \ \ L 



'I I I 



100 



50 



--3 



^ 



'^ J 







1 



5 



' 2 3 

 % of M or OSS 



5 



1 



Figure 14. Effect q/" sucrose concentration on the growth of sections in buffer without added I AA 

 [white circles, dotted lines) and with lAA (black circles, solid lines), and on the difference between these 

 growths (curves (b), (d), and (/))■ Scales are in mm (left ordinate) and in per cent of the initial ^r mm 

 length (right ordinate). 



Figure 15. Effect of pH on 

 the growth of oat sections in buffer A- 

 sucrose without lAA (white circles, 

 dotted lines) and with lAA (black 

 circles, solid lines) , and on the differ- 

 ence between the two (curves (b) and 

 id)). 



Coleoptile 



First inter node 



^ 

 ^ 



I 



J 



(b) 



\ \ 



V ^ Con. "° 



J l_J _l I L 



7 8 



J L_l_ 



361/. 



pH units 



21 



