Characteristics of an Inhibitor From Woody Shoots 



131 



X 



I- 

 o 



UJ 



100 



80 



U 60 



< 



UJ 



cr 



O 40 



UJ 



o 

 u 



20 



CONCN. OF INHIBITOR 



i 



None (water) 

 5 Internodes /ml 

 I .0 Internodes /ml. 

 10.0 Internodes/ml. 



i 



IN 



13 



INHIBITOR 



19 



Fi"-. 2. Percentage increase in growth of wheat coleoptile sections during expo- 

 sure to different concentrations of inhibitor (shaded portion at base of each 

 column) and after washing in water and subsequent incubation in 5 p.p.m. solu- 

 tion of sodium indole-3-acetate (unshaded). From left to right at each time inter- 

 val the concentration of inhibitor was (water control), 0.5, 1.0, and 10.0 mts/inl. 



Coleoptile Curvature 



While Avena coleoptile sections are affected by the inhibitor in 

 the same way as wheat sections, curvature due to lAA is much less 

 curtailed, as seen from the examples in Table 1. The inhibitor 



Table 1 . The eflFect of inhibitor on Avena coleoptile curva- 

 ture induced by 0.1 p.p.m. lAA. 



Average Curvature, Degrees 



Concentration of inhibitor (ints/ml) 



causes no curvature alone, its effect being estimated by comparing the 

 curvatures induced by agar blocks containing NalAA with or with- 

 out inhibitor; the test method employed was that of Rawes and 

 Hatcher (13). 



Wheat Leaf-Base Extension 



Using a modification of Radley's method (12), 10 mm. sections 

 were cut 2 mm. from the base of wheat coleoptiles 4 to 6 cm. long. 



