ROBERT M. MUIR 3^1 



TABLE 2 



Auxin yields from 20 mg. ovary tissue of Nicoiiana tabacum 75 hours after 



anthesis 



Ml. of Avena test Curvature 



AGAR curvature PER OVARY 



Pollinated 0.4 i6.6±i.5 184 



Unpollinated 0.4 ly.Srbi.y 198 



pollen for the production of auxin in the ovary is not part of the enzyme 

 system concerned with the transformation of tryptophan to indoleacetic 

 acid, although the possibility that it might be a part of a system re- 

 sponsible for the formation of tryptophan is not precluded. 



Further information on the production of auxin in unfertilized ovary 

 tissue of Nicotiana is obtained by incubation of the tissue at varying pW 

 levels with and without an aqueous extract of pollen as shown in Table 

 3. Small amounts of auxin are obtained from the ovary tissue incubated 

 at /?H 5.9 but large amounts are obtained if the tissue is incubated at 

 pW 8.0. This is in agreement with our knowledge of tryptophan convert- 

 ing enzymes in plant tissues, for, as Wildman et al. (19) have shown, the 

 optimal pH for the enzyme system in spinach cytoplasm is pY{ 7.5, and 

 below pH 6.0 or above pW 8.5 the activity of the enzyme is greatly 

 restricted. However, if a small amount of an aqueous extract of ground 

 pollen (containing no detectable auxin) is added to the medium, con- 

 siderable auxin is produced at pW 5.9. Apparently the auxin production 

 under acid conditions is not one of tryptophan conversion but involves 



TABLE 3 

 Auxin yields from Nicotiana tissue following incubation at 37° C. for 24 hours 



Avena test 



CURVATURE 



Buffer solution, pW 5 . 9 



20 mg. ovary tissue 5.5±i.2 



Extract of 10 mg. pollen 0.0 



Ovary tissue + pollen extract i5.odbi.3 



Buffer solution, pW 8.0 



20 mg. ovary tissue 34.6 ± 1.7 



Extract of 10 mg. pollen 0.0 



Ovary tissue + pollen extract 40.2 ± 3.2 



