238 



CHEMICAL AGENTS AND GROWTH 



D 

 25 



.2 .4 .6 a 1 



LONG DAYS i N I 



.2 -4 < -8 IP 



T 1 1 1 1 1 1 1 1 



20- 



lA- 



IjO- 



-l 0-5 



I WEEK SHORT DAYS 



2 WEEKS SHORT DAYS 



Fig. 10. Histograms corresponding to tips of the Rhus typhina plants 

 used in the experiment of Fig. 6. Methanol extracts of 25 mg dry weight 

 in each case. Chromatography on 3 MM Whatman paper strips in iso- 

 propanol (80) + ammonia (1) + water (19). Assay: oat first internodes. 

 Left, controls. Right, plants treated with about 10 /ig of GA. The posi- 

 tions of lAA and GA on the chromatograms have been indicated, as well 

 as the amount of growth obtained with 1 and 10 thousandths of a micro- 

 gram of lAA. 



As was shown in Fig. 6, when 10 /xg of gibberelHc acid was applied 

 to sumac tips, the growth rate of the plants increased under both long 

 and short days. The tips (including ail the unfolded leaves) of these 

 plants were lyophilized, extracted, and chromatographed as previously. 

 The first internode test showed that the level of the auxin which 



