Natural auxins 



Figure 9. Thimanns guillotine, which allows exact sectioning of coleoptiles and first iniernodes. 

 Avena coleopfile Sorghum first infernode Avena first internode 



13 3 



f 5 

 Tn.iri. 



yj" W 1 2 3 5 



Distance from tip or node 



Figure 10. Effect of the location o/4 mm section on the growth in sucrose+ buffer without added I AA 

 {black circles, dotted lines) and with lAA {white circles, solid lines), and on the difference of these two 

 elongations {curves {b), {d), and (/)). Left ordinate: scale in mm. Right ordinate: scale inper centof 

 the original 4 mm length. On the abscissa of the curves (c). {d). {e), and (/). 'xV means that the section 

 includes the coleoptilar node. Each point is the mean of ten replicates. 



16 



