lAA OXIDASE INHIBITOR AND MORPHOGENESIS 



155 



20 40 60 80 100 120 



FRACTION B CONCENTRATION 



(MG EQUIV. F. W./ML REACTION MIXTURE) 



mo •qui*, f. «. / aI 

 tlon mlitur* 



GO nt^ aqulv. f w. / ml 

 rtaetion mlirur* 



15 30 45 60 



FRACTION A CONCENTRATION 



(MG EQUIV. F. W. / ML REACTION MIXTURE) 



Fig. 6. Reconstitution of cofactor activity by combination of precipitate 

 (fraction B) and supernatant (fraction A): (a) supernatant constant, 

 precipitate varied; (6) precipitate constant (2 levels), supernatant varied. 



tivity is restored (Fig. 6). This situation parallels that described 

 recently by Romberger (1957) for the DPNH oxidase cofactor. 



The pea cofactor obviously differs from Waygood's wheat leaf co- 

 factor in being insoluble in ethyl ether and in yielding no active pre- 

 cipitate with basic lead acetate. 



SUMMARY 



1. A substance which inhibits lAA oxidation by the lAA oxidase 

 of etiolated peas occurs in pea buds, its synthesis being apparently con- 

 trolled by the red-far red reversible photoreaction which also controls 

 morphogenesis. This inhibitor is easily extracted from tissue by dialysis 

 of a brei or by boiling of intact tissue. 



2. In green pea seedlings, the inhibitor is most concentrated in 

 young buds, young stem and young leaf tissue. 



3. The greater the daily duration of illumination, the greater is the 

 inhibitor content of young leaves. Transfer of the plant or of excised 



