168 



A. POLJAKOFF-MAYBER 



ages were extracted and the extracts fractionated and separated 

 with the aid of paper chromatography using the conventional 

 methods for lAA isolation'-. The various parts of the chromato- 

 gram were assayed using the extension growth bioassay. The 

 results are summarized in Fig. 1. 



140 

 120H 



100 



140- 

 120 



D 100 



100 



J L 



140- 

 120t^^^ 



._^j^r^ 



01 



12 



24 



t_ 



D 



o 



48 



72 



96 



100 



O 0.1 0.2 03 0.4 0.5 0.6 0.7 0.8 0.9 1.0 /?.. 



Fig. 1. Histograms showing the chromatography separation of acid 



growth-active substances in lettuce seeds germinated for various lengths 



of time. The biossay used was the oat coleoptile extension growth test. 



The broken Hne gives the growth of the controls—. 



It is evident that dry seeds do not contain any lAA or any 

 other acid growth promoter. They do contain growth inJiibitors. 

 lAA appears between Rf 0.35-0.45, when the seedling already 

 shows appreciable development. 



Parallel to our work on the relation between growth promoting 

 and growth inhibiting substances and dormancy, other groups 

 have been engaged on the same problem. 



